ABSTRACT 
 
 
 
Title of Document: EFFECTS OF CHANNEL MORPHOLOGY ON 
FLOODPLAIN INUNDATION AND 
SURFACE-GROUNDWATER 
INTERACTIONS IN AN URBAN 
WATERSHED 
  
 Dorothea Lundberg, Master of Science, 2011 
  
Directed By: Dr. Karen L. Prestegaard, 
Department of Geology 
 
 
The purpose of this study is to evaluate groundwater-surfacewater interactions 
between a stream and the adjacent floodplain.  The study site includes two reaches on 
Paint Branch Creek: an incised reach with inset gravel bars and a non-incised reach 
with active accretion of gravels bars onto the floodplain and off channel features.  
Topography, sediment grain size and hydraulic conductivity, groundwater head, and 
floodplain/channel characteristics were measured. Groundwater head data in gravel 
bars and adjacent floodplains were monitored for one year to determine seasonal 
variations in groundwater flow directions, rates, and to develop groundwater 
probability curves. Identification of groundwater-surfacewater interactions and off 
channel features roles was determined.  In the reach with attached gravel bars, water 
flows from the creek into the adjacent gravel bars for the most of the year.  
Evapotranspiration and tropical storms influence seasonal reversals in flow directions 
between the gravel bar and the floodplain.   
  
 
 
 
 
 
 
 
EFFECTS OF CHANNEL MORPHOLOGY ON FLOODPLAIN INUNDATION 
AND SURFACE-GROUNDWATER INTERACTIONS IN AN  
URBAN WATERSHED    
 
 
 
By 
 
 
Dorothea June Lundberg 
 
 
 
 
 
Thesis submitted to the Faculty of the Graduate School of the  
University of Maryland, College Park, in partial fulfillment 
of the requirements for the degree of 
Master of Science 
2011 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Advisory Committee: 
Professor Karen L. Prestegaard, Chair 
Professor Naijun Zhou 
Professor Kaye Brubaker 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
? Copyright by 
Dorothea June Lundberg 
2011 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ii 
 
Acknowledgements 
I would like to thank my advisor, Dr. Karen Prestegaard and committee 
members, Dr. Naijun Zhou, and Dr. Kaye Brubaker for their continual academic 
encouragement in writing and conducting the research for this thesis. I am very 
thankful for the time and efforts Dr. Karen Prestegaard has provided in seeing this 
project through start to finish and giving me a chance to grow as a hydrologic 
researcher. Much gratitude goes to Alan Leslie and Marcie Occhi for their assistance 
in installing and surveying some of the piezometers needed for this research.  I would 
also like to thank my mom and dad for their love, support and daily encouragement. 
Without my parents, I would not be who or where I am today, and I am truly thankful 
to have such great parents that I can make proud.  You are the best parents a daughter 
could ask for. I love you.  
 
 
 iii 
 
Table of Contents 
 
 
Acknowledgements ...................................................................................................ii 
Table of Contents .....................................................................................................iii 
List of Tables.............................................................................................................v 
List of Figures ..........................................................................................................vi 
List of Illustrations ..................................................................................................vii 
List of Symbols ......................................................................................................viii 
1. Introduction ...........................................................................................................1 
1.1. Introduction and Definitions............................................................................1 
1.1.1. Influence of floodplain hydrology on ecological processes .......................4 
1.1.2. Effects of urbanization on floodplain processes ........................................5 
1.2. Scope of study ................................................................................................7 
1.3. Objectives.......................................................................................................7 
1.4. Review of previous studies..............................................................................8 
1.4.1. Importance of floodplains in urbanized systems .......................................8 
1.4.2. Effects of urbanization on watershed hydrology .......................................9 
1.4.3. Effect of channel morphology on floodplain hydrology..........................11 
1.4.4. Groundwater-surfacewater interactions within floodplains .....................12 
2. Study Site and Methods .......................................................................................14 
2.1 Floodplain study site ......................................................................................14 
2.2. Methods........................................................................................................15 
2.2.1. Channel cross sectional surveys..............................................................15 
2.2.2. Groundwater monitoring ........................................................................16 
3. Results.................................................................................................................23 
3.1. 2009-2010 Precipitation and stream discharge...............................................23 
3.1.1. Precipitation ...........................................................................................23 
3.1.2. Topography and grain size distribution at Site 1 .....................................24 
3.2. Identification of hydrological units................................................................27 
3.2.1. Determination of hydraulic conductivity values......................................28 
3.2.2. Spatial distributions of grain size, and hydraulic conductivity values......30 
3.2.3. Map of average hydraulic conductivity...................................................31 
3.2.4. Cross sectional view of grain size data ...................................................32 
3.3. Seasonal distributions of groundwater heads depicted as both time series 
diagrams and seasonal groundwater equipotential maps .......................................32 
3.3.1. Groundwater head data...........................................................................32 
3.3.2. Time series data of total head .................................................................33 
3.3.3. Seasonal Equipotential Maps..................................................................35 
3.3.4. Cross section diagrams...........................................................................37 
3.4. Probability distribution of groundwater heads ...............................................39 
3.5. Piezometric and stream responses to storm events.........................................41 
3.5.1. Precipitation from a major tropical storm................................................42 
3.5.2. Floodplain piezometric response to the tropical storm ............................42 
4. Discussion ...........................................................................................................45 
 
 iv 
 
4.1. Effects of channel morphology on floodplain-channel characteristics............45 
4.2. Importance of chute channels ........................................................................47 
4.3. Groundwater reversal-seasonal variations .....................................................48 
4.4. Soil hydraulic conductivity estimates ............................................................50 
4.5. Limitations....................................................................................................50 
5. Conclusion...........................................................................................................53 
Appendices A-Figures .............................................................................................54 
Appendices B-Additional Figures not used in text. ..................................................78 
Appendices C-Data..................................................................................................83 
Citations ..................................................................................................................90 
 
 
 
 
 
 
 
 
 
 
 v 
 
List of Tables 
 
Table 1: Ranges of hydraulic conductivities of sediment types.................................28 
Table 2: Hydraulic conductivities calculated from grain-size analysis.................28/29 
Table 3: Three scenarios seen in cross section equipotential diagrams of 
corresponding piezometers for Site 1 .......................................................................37 
 
 vi 
 
List of Figures 
Figure 1: Floodplain conceptual diagram .......................................................... 54 
Figure 2: Gaining and losing stream conceptual diagrams showing groundwater flow 
direction from a stream. .................................................................................... 54 
Figure 3:  Differences between an attached active floodplain and incised floodplain
......................................................................................................................... 55 
Figure 4:  Study site of intact floodplain along Little Paint Branch Creek upstream of 
the junction with Paint Branch Creek................................................................ 56 
Figure 5: Upstream study site showing gravel bars accreting onto floodplain .... 57 
Figure 6: Topography of the floodplain adjacent to the stream channel. ............ 58 
Figure 7: Precipitation at the Beltsville Gauge for the study period. .................. 59 
Figure 8: Cumulative precipitation for the Beltsville Gauge.............................. 59 
Figure 9: Daily Average discharge in little Paint Branch................................... 60 
Figure 10: Examples of soil profiles used to find D10 and D50 values.............. 61 
Figure 11: Hydraulic conductivity values and average D50 values for Site 1..... 62 
Figure 12: Soil profile- (A) floodplain soil profiles; (B) upland soil profiles ..... 63 
Figure 13: Transect time series ......................................................................... 64 
Figure 14: Site 2 Water Level Elevations. ......................................................... 65 
Figure 15: Complete time series........................................................................ 66 
Figure 16: Site 1 equipotential maps-Seasons. .................................................. 67 
Figure 17: Site 1 equipotential maps-Summer/Fall conditions........................... 68 
Figure 18: Site 1 equipotential maps-Winter/Spring conditions......................... 69 
Figure 19: Seasonal groundwater flux............................................................... 70 
Figure 20: Site 1 Groundwater elevation plots .................................................. 71 
Figure 21: Seasonal change in groundwater head.............................................. 72 
Figure 22: Annual flow duration curves............................................................ 73 
Figure 23: Site 1 equipotential maps-Highs and Lows conditions...................... 74 
Figure 24: Time plot of fall tropical storm ........................................................ 75 
Figure 25: Detailed time plot of fall tropical storm (15 min intervals) ............... 75  
Figure 26: Hyetographs distribution of rainfall with time.................................. 76 
Figure 27: Tropical storm time series graph ...................................................... 77 
A1: Extra complete time series ......................................................................... 78 
A2: Extra complete time series ......................................................................... 79 
A3: Extra groundwater elevation plots.............................................................. 80 
A4: Extra groundwater elevation plots.............................................................. 81 
A5: Extra annual flow duration curves.............................................................. 82 
 
 
 
 
 
 
 vii 
 
List of Illustrations 
Illustration 1: Photo showing floodplain characteristics of Site 1 ...................... 25 
Illustration 2: Photo looking down chute channel for Site 1 .............................. 26 
Illustration 3: Photo-various channels during storm event on Site 1 ............. 26/41 
Illustration 4: Photo showing evapotranspiration............................................... 36 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 viii 
 
List of Symbols 
K  Horizontal hydraulic conductivity 
AH   Dimension coefficient (= 1.0 for m/d) 
C  Empirical constant 
T  Temperature 
D10   Effective grain size 
I0  Intercept of grain size distribution curve between D10 and D50 
D50   Median grain size 
V  Darcy velocity 
dh/dl  Horizontal groundwater gradient 
Q  Groundwater discharge 
A  Area of groundwater flow 
 
 1 
 
1. Introduction 
1.1. Introduction and Definitions 
 Stream valleys commonly contain floodplains, active stream channels, and 
sometimes abandoned floodplains or terraces.  Leopold et al., 1964, defined 
floodplains as valley flats built and maintained by an active channel.  Junk et al., 
1989, added a hydrologic component to the definition: floodplains are periodically 
inundated by lateral overflow, direct precipitation, or groundwater inputs (Figure 1).  
Stream channels build floodplains by either (or both) lateral migration or vertical 
accretion of sediment carried onto the floodplain.  Models of floodplain development 
are based on these sediment depositional styles.  Common floodplain evolution 
models include meander migration as a driving force (through bank erosion and point 
bar formation or overbank deposition as an accretion mechanism (e.g. Howard, 
1992).  Although models of floodplain formation have mainly addressed meandering 
rivers, floodplains, form along most rivers, with a variety of plan-view morphologies 
and accretion mechanisms.  In more recent years, rivers and their floodplains have 
been studied as integrated channel-floodplain systems that influence sediment, water, 
and organic budgets (Junk et al., 1989).  
Most definitions of active alluvial channels emphasize that they are self-
formed and that they tend towards equilibrium or quasi-equilibrium morphology 
(Lane, 1955; Leopold et al., 1964).  Given a naturally-varying range of discharge and 
sediment characteristics, fluvial geomorphic systems appear to maintain equilibrium 
channel geometry through time, although the channel form may migrate through 
 
 2 
 
space (Hack, 1960; Leopold et al., 1964; Osterkamp and Hedman, 1977; Knighton, 
1998).  This quasi-equilibrium condition is defined as an equilibrium channel form 
(although not position), that is maintained while neither aggrading nor degrading the 
bed (Strahler, 1957; Hack, 1960; Leopold et al., 1964). No explicit equilibrium 
conditions have been defined for the hydrologic processes in the channel-floodplain 
system. 
Recent research on hydrologic interactions between floodplains and stream 
channels has focused on documentation of various hydrological processes (e.g. 
evapotranspiration, groundwater response to precipitation, etc.) or on evaluation of 
the hydrological connectivity between floodplains and stream channels (e.g., Poole, 
2006; Lautz, 2008; Park 2008).   Groundwater systems, in particular, can provide 
continuous exchanges between stream water and adjacent groundwater flow systems.   
Groundwater and stream water can interact in several ways (Figure 2). First, 
groundwater can flow through the floodplain and discharge into the stream.  In this 
case, stream baseflow discharge increases downstream between tributary inputs, 
creating a ?gaining? stream segment.  Alternatively, stream water can flow into the 
adjacent floodplain or hyporheic zone under the stream.  This creates a ?losing? 
stream that recharges the local groundwater system.  A third condition is a floodplain 
aquifer that transports groundwater largely parallel to the stream.  Stream-floodplain 
flow directions can be spatially and/or temporally heterogeneous. Both gaining and 
losing stream segments can exist within the same stream system or at various times 
within the same stream reach (Winter et al., 1998; Woessner, 2000; Sophocleous, 
2002).  Flow directions of floodplain groundwater depend on the distribution of 
 
 3 
 
hydraulic heads relative to the stream surface elevation. In a gaining stream, the 
elevation of the groundwater is higher than the elevation of the stream water surface.    
The opposite is true for losing streams. Seasonal variations in precipitation patterns 
and/or evapotranspiration can alter the stream levels relative to groundwater 
elevations, and thus groundwater flow directions.  
The timing, magnitude, duration and frequency, and source of water to 
floodplains reflect both local floodplain processes and the overall watershed 
processes (Poff et al., 1997; Wroblicky et al., 1998; Malard et al., 1999; Wondzell 
and Swanson, 1999).  Floodplain characteristics, (Poff et al., 1997), climate, 
hydrologic processes, erosion and aggradation, land use channel morphology, and 
hydrological events affect streamflow, sediment transport, and exchanges of water 
and sediment between the stream and floodplain (Johnson et al., 1976; Tyus, 1990; 
Hill et al., 1991; Sparks, 1995; Castleberry et al., 1996; Stanford et al., 1996; Richter 
et al., 1997). Floodplains can regulate surface runoff rates and amounts (Woessner, 
2000; Butturini et al., 2002), and can provide sources or storage of water during 
hydrological extremes (Wondzell and Swanson, 1999; Sophocleous, 2002; Krause 
and Bronstert, 2004, 2007).   
A limited number of studies have identified the hydrological pathways, 
particularly groundwater flow patterns, within floodplains (Nortcliff and Thornes, 
1984; Hill, 1990; Haycock and Burt, 1993; Waddington et al., 1993; Squillace, 1996; 
Burt, 1997; Mertes, 1997; Burt et al., 1999).  Due to their topographic location and 
geomorphology, most floodplains are characterized by shallow water table levels. 
Gillham, (1984), Burt and Haycock (1996) and Burt (1997) have described the water 
 
 4 
 
balance of a floodplain in significant detail.  Floodplain water tables are maintained 
by a variety of hydrologic processes including: tributary inflow, groundwater 
discharge from local or regional flow system, inflow from the channel (overbank 
bank inundation, etc), and direct precipitation, which is especially important in large 
floodplains.  Low hydraulic gradients and often complicated hydraulic gradients 
within floodplains help to sustain saturated conditions, especially in wide, complex 
floodplains.  Flow directions between floodplain groundwater and surface streams 
can change seasonally or during storms as the elevation of the groundwater changes 
with respect to the stream-surface elevation (Rosenberry and Winter, 1997; Zhang 
and Schilling, 2006). With continued evapotranspiration and lower contributions of 
groundwater from hill slopes, hydraulic gradients may reverse from flowing towards 
the stream during winter conditions to a summer condition, with discharge from the 
river to the floodplain (Haycock and Burt, 1993; Bates et al., 2000; Burt et al., 2002. 
In the lower reaches of some watersheds, including coastal streams such as Little 
Paint Branch, floodplains can remain inundated for long periods such as weeks to 
month (e.g., Benke, 2000). Therefore, floodplains often support seasonal wetlands 
with saturated conditions that persist throughout the year (Burt, 1997). 
1.1.1. Influence of floodplain hydrology on ecological processes 
The importance of hydrology in controlling riparian zone functions has been 
reviewed by Haycock et al. (1997), Hill (1997), and Cirmo and McDonnell 
(1997).Floodplains are also important sites for biogeochemical alteration of solutes 
and particulates, such as nutrients and pollutants (Lowrance et al., 1984; Triska et al., 
1989, 1993; Duff and Triska, 1990; Haycock and Burt, 1993; Gilliam, 1994; 
 
 5 
 
Lowrance et al., 1995; Hill, 1996; Brunke and Gonser, 1997; Komor and Magner, 
1996).  Exchanges between surface and groundwater sources have significant 
influence on structural and functional quality of stream ecosystems (Brunke and 
Gonser, 1997) and are produced by physical and biological processes. 
Hydrological processes (e.g. surface water dynamics, groundwater flux, etc.) 
affect local soil moisture characteristics that can affect biological heterogeneity and 
diversity of flora and fauna in floodplain systems (Bencala, 2000).  Channel bars, 
channel steps, flow obstacles (i.e., debris), and meander bends are all features that 
generate local hyporheic flow (Hendricks & White, 1988; White, 1990; Harvey & 
Bencala, 1993; Wroblicky et al., 1998). These geomorphological units are often sites 
with high rates of hydrological exchange with the surface stream. Due to grain size 
heterogeneities and permeability variation, different sediment bars can provide a 
range of hydrological exchange rates within the stream system (Rouch, 1992).  Thus, 
variations in channel geomorphology and sediment permeability can result in a 
variety of hydrological processes and hydrological exchange rates.  Inter-relationships 
among the hydrological and biological systems can be complex.   Therefore, 
disruption in individual system components can have short and long term effects on 
ecological processes.   
1.1.2. Effects of urbanization on floodplain processes 
Urbanization, particularly in unmitigated watersheds, often causes an increase 
in storm runoff, which can affect channel morphology, sediment mobility, and the 
relationship between the channel and the floodplain (Leopold et al., 1964; Hammer, 
1972).  Common stream responses to urban runoff include channel widening 
 
 6 
 
(Hammer, 1972) and channel incision (Rosgen, 1994).  Incised stream channels can 
contain floods larger than the bankfull (~1.5 years recurrence interval) within the 
channel, resulting in high shear stress during flood flows, which can lead to further 
channel incision (Darby and Thornes, 1992; Hupp, 1992). The bed erosion that 
creates incised channels may facilitate drainage of the groundwater from the 
floodplain.  These hydrological changes, particularly the lowering of groundwater 
tables and changes in the frequency of floodplain inundation result in only one 
direction of groundwater flow: from the floodplain to the channel (disconnection of 
the floodplain). These hydrological changes may cause decreases in nutrient and 
sediment retention along channelized reaches (Noe and Hupp, 2005) which may 
translate into accelerated storage of sediment and nutrients in channels and 
floodplains downstream of incised reaches (Darby and Thornes, 1992; Shankman and 
Smith, 2004; Noe and Hupp, 2005).    
Modification of channel morphology therefore can influence exchanges of 
water, sediment, and nutrients between surface and groundwater systems (Harvey and 
Bencala, 1993; Wondzell and Swanson, 1996; Hill et al., 1991, Wroblicky et al., 
1998, Wondzell and Swanson, 1999).  Recently, restoration scientists have begun to 
consider the role of floodplain hydrology in restoration designs (e.g. Kaplan et al., 
2010).  For example, ?cutting down the floodplain? is a procedure used to facilitate 
water, nutrient, and sediment exchanges between the floodplain and channel (Palmer 
et al. 2005). Restoration of exchanges between floodplain and channel can also occur 
due to natural deposition of sediment bars on the stream beds and banks. These 
attached sediment bars (of gravel, sand, etc.) can build up the channel bed and 
 
 7 
 
accomplish these re-connections without causing disturbances of the natural 
floodplain.   Although the effects of urbanization on channel morphology have been 
examined for several decades, the long-term effects of urbanization on floodplain 
hydrology and hydroecology have only recently gained attention. 
1.2. Scope of study 
The purpose of this study is to examine floodplain hydrological processes in 
an urban stream channel that has undergone a series of morphological changes.  The 
study is conducted on a channel-floodplain remnant of a once extensive floodplain 
along the Northeast Branch of the Anacostia River and its tributaries. The stream 
channel in the Little Paint Branch watershed has experienced widening, channel 
incision, and recently local aggradation and formation of sediment bars in and along 
the channel (Blanchet, 2009).  Stream channel incision and sediment characteristics 
of the floodplain and stream channel provide major local controls on fluxes between 
the stream and the adjacent floodplain (Figure 3). 
1.3. Objectives 
In this study, the processes that influence exchanges of water between a 
stream and floodplain are examined in Little Paint Branch creek, which is a tributary 
to the Anacostia River, MD.  Although two sites are examined, most of the study will 
focus on the upstream site where recent channel aggradation has caused bar formation 
to build up the level of the floodplain and re-attach the channel to the floodplain. I 
hypothesize that these attached gravel bars facilitate exchanges of water between the 
channel and the floodplain.  The other site contains an incised channel with a low 
 
 8 
 
width to depth ratio and high banks that restrict overbank flooding deposition. A 
gravel bar is also present at this site, but I hypothesize that it does not facilitate 
exchanges with the floodplain.  The objectives of the study are: 
1.  To evaluate water exchanges between the stream channel and adjacent floodplain 
by examining stream water surface elevation and groundwater heads for sites with 
incised and non-incised channel morphology. 
2.  To examine seasonal variations in groundwater flow directions in the floodplain 
and stream channel sediment bars. 
3.  To evaluate the effects of storm events on groundwater flow directions and rates. 
 
1.4. Review of previous studies 
1.4.1. Importance of floodplains in urbanized systems  
Floodplains can provide temporary and long term storage for water, sediment, 
and contaminants (Hupp et al., 2008).  Vegetation and soils within a floodplain can 
store, transform or filter pollutants; shade and cool the stream; and reduce flood by 
storing or reducing the velocity of flood waters.  Within a river-floodplain system, 
stream banks, chute channels, and other features are created and maintained through 
the wide range of stream discharges.  Stream channels and floodplains and gravel bars 
are formed and maintained by both bankfull and overbank discharges (Poff et al.,, 
1997) that carry sediment, and thus modify the channel and floodplain (Wolman and 
Miller, 1960). Streams with a low range of bankfull flows intensities, have active 
floodplains that often migrate laterally and thus maintain the morphology of the 
floodplain (Leopold et al. 1964).  Streams with a wide range of flood flows produce 
 
 9 
 
floodplains that contain major bar deposits formed during large flood events (Miller, 
1990). Urbanized streams (e.g. Little Paint Branch), in particular, show signs of 
increased magnitude and frequency of high flows (Hammer, 1972), downward 
incision and floodplain disconnection (Prestegaard, 1988), reduced baseflows, bank 
erosion and channel widening (Hammer, 1972) and reduction in the infiltration ability 
of the soils within the floodplain (Dunne and Leopold, 1978).  
Floodplains are natural buffer zones alongside stream channels (Hill 1996; 
Lowrance et al., 1995), creating hotspots of ecological function within an area of 
urbanization. There is tremendous variability of the conditions of urban streams and 
floodplains, depending on historic development, redistribution of sediments, and the 
overall hydrogeologic conditions of the watershed (Booth, 1990; Trimble, 1997; 
Pizzuto et al., 2000). However, the conversion of floodplains to urban land use and 
the subsequent increase in impervious surfaces within the watershed cause stream 
incision. Incised streams in urban watersheds are typically disconnected from their 
floodplains (Riley, 1998; Booth et al., 2001), and possess low riparian groundwater 
levels. Reduction in groundwater levels then drastically affects soils, plants, and the 
microbial processes found in floodplains (Groffman and Crawford, 2003) by 
increasing the area of unsaturated soil levels below the surface. The watertable within 
a floodplain is critical for control of the ecosystem structure and function.   
1.4.2. Effects of urbanization on watershed hydrology 
Urbanization is one of the most dramatic alterations of ecosystems (Grimm et al. 
2000; Pickett et al., 2001). Streams and groundwater are particularly vulnerable to 
altered hydrology in urban landscapes. The increase in impervious surfaces can alter 
 
 10 
 
the rates and flow of water moving into, through, and out of stream and groundwater 
systems (Arnold and Gibbons, 1996; Dale et al., 2000; Paul and Meyer, 2001). These 
impervious surfaces decrease interception, infiltration, percolation and storage of 
water in watershed, which leads to increased runoff during storm events (Dunne and 
Leopold, 1978). Watersheds with large amounts of impervious cover typically 
experience decreases in groundwater recharge, stream base flow, and surfacewater 
groundwater connectivity than undeveloped watersheds (Lazaro, 1990, Bohlen and 
Friday, 1994; Braune and Wood, 1999; Paul and Meyer, 2001).   
Stream and floodplain systems are responsible for the transfer of energy and 
materials (Gleick, 1998; Palmer, 2000; Naiman et al., 1995). Urbanization of 
watersheds can decrease baseflow and increase the magnitude of floods (Groffman et 
al., 2003; Walsh et al., 2005).  Geomorphic alterations, and nutrient pulses are two of 
the specific effects on the floodplains ecosystem attributes due to flooding events 
(Tockner et al., 2000).  Geomorphic alterations specifically, may impact the 
interactions of the channels with the floodplains and the depth to the groundwater 
table in floodplains.  Changes to groundwater table and interactions between 
surfacewater and groundwater have effects on floodplain functions and ecological 
processes (Groffman et al., 2003).   
Overbank flooding and floodplain features such as riparian vegetation, chute 
channels, soils characteristics are closely mutually dependent and these physical 
characteristics shape the amount of overbank flooding, flows and patterns.  The 
amount of overbank flooding also depends on direct rainfall, tributary water, runoff 
from the nearby upland areas, and height of groundwater tables (Tockner et al., 
 
 11 
 
2000).  The patterns of overbank flooding can affect topography and soil 
stratification.  Flood discharges that spill onto floodplains can recharge local 
groundwater, therefore, gravel bar formation and floodplain accretion, are important 
channel processes that mediate the connectivity of channels to the floodplain.   
1.4.3. Effect of channel morphology on floodplain hydrology 
Channel morphology is influenced by sediment input of upstream sources and 
ability of the channel to transport sediment loads to downstream reaches. Potential 
channel adjustments in response to altered discharge and sediment load include 
changes in width, depth, velocity, slope, roughness, and sediment size (Leopold and 
Maddock, 1953).  Wide, shallow channels have more contact with the bed, which 
creates an increase in friction. Incised channels have less friction due to low contact 
with channel bed. Natural channels increase in width when sediment supply exceeds 
transport capacity. Smooth stream bottoms allows for higher velocities while gravel 
slows the flow.  The size of particles on the streambed is a function of the gradient 
and confinement.  
Channel morphologies have been comprehensively studied and classified 
(Shumm, 1963; Church, 1992; Rosgen, 1994). Change in stream channel morphology 
caused by watershed land-use change and channelization, is the basis of river and 
riparian ecosystem degradation (Naiman et al., 2005; Steiger et al., 2005). Channel 
morphology is the principal determinant of streamflow and sediment transport rate, 
where sediment transport rate equals sediment supply (e.g., Lane, 1955; Blench, 
1957; Schumm, 1971). Changes in channel morphology that alter groundwater-
 
 12 
 
surfacewater interactions between the stream and floodplain can change soil and 
groundwater flow regimes across the floodplains (Loheide and Booth, 2010).   
1.4.4. Groundwater-surfacewater interactions within floodplains 
Patterns of surfacewater and groundwater interactions across floodplains are 
shaped by local and regional watershed and stream channel geomorphology and 
hydrology. The degree of interaction is determined by the sediment characteristics 
and hydraulic conductivity of the streambed and associated floodplain soils (Valett et 
al., 1996, Dahm et al., 1998, Boulton et al., 1998).  Understanding surfacewater-
groundwater interactions require the identification of groundwater flow paths and 
their connectivity to streams, rates of exchange between stream and groundwater 
systems, and seasonal variations (Wroblicky et al., 1998). 
Geomorphic characteristics, such as off-channel features (chute channels) and 
topographic structures of the streambed and floodplains, can influence groundwater 
and surface-subsurface rates and patterns within the associated floodplain?s hyporheic 
zone (Harvey and Bencala, 1993; Wondzell and Swanson, 1999; Woessner, 2000; 
Kasahara and Wondzell, 2003; Anderson et al., 2005; Gooseff et al., 2006a,b; Poole 
et al., 2006). In addition, timing, duration, magnitude, and source of water input and 
delivery across the floodplain influences the groundwater fluctuation (Wroblicky et 
al., 1998; Malard et al., 1999; Wondzell and Swanson, 1999).  
Hydrologic studies done at small scales focus on near stream interactions with 
a particular focus on stream geomorphic characteristics, such as bed form and its 
influence on the hydrologic exchange between streams and their associated floodplain 
groundwater systems. Studies have documented hydrologic relationships focused on 
 
 13 
 
either variation in groundwater flow pathways with changing river stage (Wondzell 
and Swanson, 1996, Wroblicky et al., 1998; Malard et al. 1999) or on the variation in 
geomorphic structure and patterns (Harvey and Bencala, 1993; Wroblicky et al., 
1994; Wondzell and Swanson, 1999; Kasahara and Wondzell, 2003). Harvey and 
Bencala, (1993) established that topographic variations in stream mountain 
catchments are hydrologically isolated at the head of riffles pools from floodplain 
groundwater under baseflow conditions. Another study showed that meander bends in 
streams are expected to generate floodplain flowpaths depending on their orientation 
relative to the local groundwater flow system (Larkin and Sharp, 1992). Another 
study showed that hyporheic flow in coarse-grained rivers have been conducted, 
mainly through field experiments and modelling (Harvey and Bencala, 1993; 
Wondzell and Swanson, 1996; Worman et al., 2002; Storey et al., 2003; Gooseff et 
al., 2006a,b). Although multiple studies strengthen the view of the hyporheic zone as 
a dynamic system (Gibert et al. 1994, Jones and Mulholland 2000), studies that 
consider geomorphology and groundwater flow regime concurrently (Henry et al. 
1994, Storey et al. 2003) are scarce and analyses on larger gravel dominated 
floodplains excluding Poole et al. (2006). 
 
 
 
 
 
 
 14 
 
2. Study Site and Methods  
 
2.1 Floodplain study site  
The purpose of this study is to examine the effects on channel morphology 
and sediment bar accretion on the interactions between stream flow and groundwater 
flow in a floodplain-channel system.  Therefore, requirements for the study site 
include:  a) presence of an intact floodplain, b) variations in stream channel 
morphology within the floodplain site, and c) lack of rip-rap or channelization 
features that could influence channel-floodplain interactions. With these criteria in 
mind, a study site was chosen along the lower reaches of Little Paint Branch, a 
tributary of the Northeast Branch of the Anacostia River (Figure 4).  The relationship 
between the channel and floodplain changes along the length of the study reach.  The 
upstream portion of the site is not incised and the stream flows overbank during 
bankfull and higher flood events.  The downstream reaches of the river are incised 
and overbank flooding is less frequent.  Both sites have been gauged, thus partial 
hydrographs are available for storm events at the upstream and downstream locations.   
 
Two sites were chosen within the floodplain-channel system in which to 
monitor groundwater flow and its relationship to the stream (Figure 4).  The upstream 
site is at the location of active gravel bar formation.  Blanchet (2009) found that bar 
formation has caused shoaling of the channel bed and that the river overtops the 
banks 3-4 times per year.  At the downstream site, gravel bars are inset into a channel 
with higher banks than those at the upstream reach.  Site 1 at the upstream reach has 
 
 15 
 
banks ranging from 0.01 to 1 meter above streambed whereas at Site 2 the bank 
height ranges from 0.6 to 1.56 meters above streambed. During the study period, 
overbank flooding occurred only during very large flood events, while the upstream 
site exhibits overbank flooding during bankfull and higher events that have occurred 
several times a year during the study period. 
 Gravel bars have recently formed and accreted onto the floodplain at the 
upstream site; this creates a veneer of gravel and sand over the floodplain sediments 
(Blanchet, 2009).  At depth, both the stream bed and adjacent floodplain are underlain 
by compacted fine-grained (clay) sediment.  Along the stream, this clay layer is 
overlain by sand and gravel.  The recently accreted gravel bars have created a bar and 
chute topography.  The small chute channels carry flow from Little Paint Branch onto 
the floodplain during flow events, including events that are below bankfull stage.  
The largest of the adjacent chute channels runs parallel to the channel in the 
northwest corner of the study site (Figure 5A). There are also two active gravel bars 
present at this site (Figure 5A.-a, c). Figure 5B shows the downstream study site and 
gravel bars.  
2.2. Methods  
2.2.1. Channel cross sectional surveys  
Channel and floodplain topography was surveyed to determine channel 
elevations and the relationship of the channel morphology to the adjacent floodplain.  
This survey included a total of 11 channel-floodplain transects.  A tripod was setup at 
a central location and multiple transects were surveyed using a surveying level.   
Horizontal distances along each transect were measured with a taut measuring tape 
 
 16 
 
that extended from along the entire transect of the floodplain-channel system.  A 
stadia rod was used to obtain the elevations measurements and was held along the 
bottom of the stream bed or floodplain topography. Topography was measured at 1 m 
interval across both the floodplain and stream channel. 
2.2.2. Groundwater monitoring 
2.2.2.1. Piezometer installation:  
At both sites, piezometers were installed in a series of transects that extended 
from the stream edge into the adjacent floodplain.  The locations of the piezometer 
transects were chosen to provide groundwater elevations and flow directions in the 
floodplain. Groundwater piezometers were installed on both vegetated and non-
vegetated gravel bars.  The upstream site, Site 1, includes eight transects, labeled A-H 
and the downstream site, Site 2, contains five transects labeled V-Z.  Transects varied 
from one piezometer to eight piezometers.  The length of the sites and the width of 
the monitored sites were determined by the length and width of the gravel bars.  
Distances between piezometers in each transect ranged from 4 to 6 meters.  Distances 
between transects varied from 12 to 20 meters. A total of fifty-one piezometers were 
installed at Site 1.  A total of nine piezometers were installed at Site 2.  The 
differences in size of the piezometer networks are based on the observed stream water 
excursions onto the floodplain at the two sites as well as floodplain size. A simplified 
version of the topographic map of Site 1 is shown in Figure 6 along with the location 
of the piezometers.  Piezometers are distributed along transects between the stream 
and the higher level floodplain.  The map also shows the position of the chute channel 
that enters the stream above the study site and reenters the stream slightly 
 
 17 
 
downstream of the study site.  This chute channel conveys a secondary channel 
during flood events and is active at least four times a year.  Cross section 
equipotential diagrams will show the relationship between flow in the chute channel 
and the adjacent groundwater during high flow periods.  Piezometers were installed in 
holes bored with a 2.54cm auger to a depth of approximately 1.3 meters. All the 
piezometers were installed above the basal clay layer and were installed to depths at 
or greater than the mid summer water table, which is the expected minima for the 
period of study.  Each piezometer was ventilated to allow for proper pressure 
equalization with the insertion of a hole near the top of each piezometer in the above 
ground section. 
 2.2.2.2. Surveys of ground surface and piezometer elevations: 
After the piezometers were installed, the ground surface and piezometer 
elevations were surveyed starting at the stream bank.  Elevations of the ground 
surface was measured at one meter intervals along transect locations using a stadia 
rod.  At each piezometer, the elevations of each piezometer top and base were 
surveyed in order to depict piezometer locations along transects. Once again a 
measuring tape was stretched from the stream bed to approximately 2 meters passed 
the last piezometer in each transects. The tripod was minimally relocated in order to 
avoid error in calculating back sites and foresights.  
2.2.2.3. Monitoring of Piezometric head: 
Measurements were taken from July 15th, 2009 through August 19th, 2010 in 
the morning hours between 9am and 11am to minimize diel influences. Total head in 
the piezometers was determined using a steel measuring tape that was used to 
measure the depth of water in the piezometers relative to the top of the piezometer.  
 
 18 
 
Measurements were made at least once a week to determine seasonal variations.  
Measurements were also made before, during, and following a storm event in late 
September to October to determine piezometric response to a tropical storm. Total 
head is calculated from the water depth measurements: 
Total Head = Piezometer Bottom Elevation + Depth of water in piezometer 
2.2.2.4. Determination of hydraulic conductivity:  
 Hydraulic conductivity is a property of both the fluid and the porous media. 
Hydraulic conductivity can be measured in the lab, measured in the field, or estimated 
from grain size.  In shallow groundwater systems, the presence of macropores 
increases the hydraulic conductivity of silt, clay, and mixtures of sand, silt and clay.  
Thus, the hydraulic conductivity is not a simple function of grain size and hydraulic 
conductivity should be measured in-situ.  Macropores, however, collapse in coarse 
sediment (sand and gravel) and thus hydraulic conductivity is more closely related to 
grain size for study site such as this one.  Due to the high hydraulic conductivity, slug 
tests are often difficult to conduct for sand and gravel mixtures as found at Little 
Paint Branch field site.  Therefore, hydraulic conductivity was estimated from grain 
size.    
Samples of gravel bar sediments and floodplain soils were collected along 
each transect.  Samples were collected for each geomorphic surface along each 
transect.  In all, 14 samples were collected and analyzed to determine grain size 
distribution, which was used to estimate hydraulic conductivity. Once collected, 
samples were taken to the lab and spread out within individual trays and allowed to 
air dry for two weeks.  Sediments were sieved to determine particle size distributions.  
Nested sieves at half phi intervals (16mm through 0.063 mm) were used to determine 
 
 19 
 
the weight percentage in each size class.   Grain size distributions were plotted as 
semi-logarithmic graphs to determine grain-size distribution curves and grain size 
statistics for each sample. Empirical relationships were then used to estimate 
hydraulic conductivity from standard grain size parameters. The grain size diameter at 
which 10% of the sediment is finer (D10) could be applied using empirical formula, 
initially developed by Hazen (1892): K=AHCT(D10)2 (Equation 1) where AH is a 
dimension coefficient (= 1.0 for m/d), C is an empirical constant (=860) and T is a 
temperature correction factor (=1 at 10? C).  A second empirical relationship that 
utilizes the grain size distribution was also used.  This empirical relationship,  
developed by Alayamani & Sen (1993), uses the slope and intercept (I0) of the grain 
size distribution curve between D10 and the median grain size (D50):  K= 1300(I0 + 
0.025(D50-D10))2  (Equation 2).  Where K is the hydraulic conductivity (m/day), Io is 
the intercept (in mm) of the line formed by D50 and D10 with the grain-size axis, D10 is 
the effective grain diameter (mm), and D50 is the median grain diameter (mm). 
  2.2.2.5. Analysis of groundwater head data 
 Groundwater head was analyzed by a) plotting time series graphs of total head 
data to determine seasonal changes in groundwater heads, b) by constructing 
groundwater probability graphs that depict the amount of time that the groundwater 
table is at various depths below the ground surface, and c) by constructing flow nets 
of equipotential and flow lines of groundwater flow in the floodplains.    
Time series graphs of total head 
During the course of study period between July 15th, 2009 and August 19th, 
2010, each measurement of total head for each piezometer was graphed as a function 
of time to obtain time series graphs of water table elevations for each piezometer.  
 
 20 
 
Over the period of the study, these time series measurements were used to determine 
seasonal variations in the elevation of the groundwater table. Seasons were broken 
down as follows: June, July, August for the summer season; September, October, 
November for the fall season; December, January, February for winter season; March, 
April, May for the spring season. In addition, the data was used to evaluate steady 
state conditions in addition to identify storm influences indicated by peaks in the time 
series graphs during the year. Piezometer total head data from steady state periods can 
be used to determine equipotential maps of the water surface. 
2.2.2.6. Construction of flow nets: 
Flow nets were constructed from equipotential maps of groundwater head that 
are used to determine groundwater flow directions. These maps were constructed 
using the topographic base map and head data for individual dates and piezometers 
using ArcGis version 10.0 (ESRI, Redlands, California, USA). Maps were made for 
steady state conditions determined from time series data over the past year to depict 
groundwater flow. High groundwater conditions during winter and summer months, 
and low groundwater conditions of late summer, have also been constructed.   
The groundwater flow nets and hydraulic conductivity data were used to 
determine groundwater flow in the flood plain.  For each steady state condition, 
groundwater flow rates were determined using Darcy?s law:  v = K(dh/dl).  Where K 
is the horizontal hydraulic conductivity, dh/dl is the difference in height over the 
change in length, and v is the Darcy velocity.  Groundwater discharge carried by the 
floodplain is calculated as:   Q = vA = A*K(dh/dl).  Where A is the cross sectional 
area perpendicular to flow, this analysis can be simplified through the use of flow 
nets.   
 
 21 
 
 
2.2.2.7. Use of GIS to determine flow patterns and elevations 
ArcMap was used to determine the flow patterns and elevation gradients along 
Little Paint Branch floodplain. Using the results from the time series graph created 
above, steady state conditions for each season was obtained as well as the year?s high 
and low conditions. These six conditions and corresponding dates were then 
formatted in a excel spreadsheet. In addition to adding a shapefile of a satellite map of 
Little Paint Branch, I added tabular data that contained geographic locations in the 
form of x,y coordinates to the map.  Latitude and longitudinal values were determined 
using Google Earth and then the values were converted to decimal degrees.  In order 
to have spatial reference, the longitude and latitudes were projected from GCS North 
American 1983 coordinate system, state plane of Maryland, creating a shapefile. 
In order to minimize ArcMap response and estimation, the study site was 
fitted with a mask that encompasses the piezometers. Two masks were created, a full 
mask with all the piezometers, and a partial piezometer mask to accommodate the 
partial data set of piezometers from July to December.  Some steady state conditions 
had data for all piezometers for the full year, where as some piezometers were 
installed later in the study consisting of half of a year worth of data for each 
piezometer.  These masks were fitted based off the area surrounding the piezometers 
and minimized empty space.  Setting an analysis mask allowed processing of only the 
selected locations. All other locations were assigned values of NoData and cells with 
values were only considered in the interpolation. 
The water level elevations were then interpolated using kriging spatial 
analysis. Kriging interpolation uses geostatistical models including autocorrelation. 
 
 22 
 
Kriging allowed for the surface prediction while providing some measure of certainty 
or accuracy of the predictions. Kriging assumes the direction between piezometer 
points reflects a spatial correlation that can be used to explain variation. The Kriging 
tool was set to the specified points located with the determined mask and given an 
output value for each location. Using a Gaussian influenced semivariogram depicting 
the spatial autocorrelation of the sampled piezometers, the nugget (intercept of y-
axis), range (where model flattens), sill (value on y-axis at range) and lag size (size of 
a distance class) were calculated and added into the interpolation. Each of the six 
conditions were fitted to a kriging interpolation output and displayed with use of four 
classification groups determined by natural breaks.  Natural classes are based on 
natural cluster present in the data. ArcMap identifies break points by picking the class 
breaks that best group similar values and maximize the differences between classes. 
The features were then divided into classes whose limits are set where there are 
values relatively different. 
 Using the contour lines function and the created kriging interpolation output 
raster, equipotential lines were created based off of the piezometers hydraulic head 
elevational values with intervals of 0.05 and 0.1 meters.  This was completed for 
every condition for both sites. Next 3D maps were created using ArcScene using the 
kriging interpolation from the previous step.  Here the layers were stacked on top of 
each other based on the kriging output to show the water levels and topography over 
the course of time in a 3D view.  
 
 
 
 23 
 
 
3. Results  
 
 
The results section is organized as follows: 1) Hydrological framework 
(precipitation and streamflow), 2) Hydrostratigraphic units, 3) Seasonal distributions 
of groundwater head depicted as both time series diagrams and seasonal groundwater 
equipotential maps, 4)  Probability distributions of groundwater head at various 
distances the channel, and 5) Response to fall storm event.  
3.1. 2009-2010 Precipitation and stream discharge 
3.1.1. Precipitation  
Precipitation data were obtained from the NWS Beltsville gauge.  A total of 
111.6 cm of precipitation occurred throughout the monitoring period from July 15th, 
2009 to August 19th, 2010 with a mean of 0.24?0.76 cm (Figure 7), which 
corresponds to an annual precipitation of 80.2 cm.  Precipitation in Maryland does not 
usually exhibit pronounced seasonality, and this was observed during the study 
period, note the nearly constant slope of the cumulative precipitation diagram (Figure 
8).   
Major storm events generated overbank flooding onto the floodplain and 
activation of the chute channel, which also brought water into the floodplain. 
Although baseflow showed some seasonal variation (Figure 9), overbank flooding 
was generated only by storm events. A minimum of 2.2 cm of precipitation per day 
appeared to be required to initiate overbank flooding events.  Daily precipitation 
 
 24 
 
exceeded 2.2 cm seven times during the study period.  These major storms occurred 
in both summer and winter periods.  In late summer, tropical storms occurred on: 
9/26/09, 8/12/2010, 8/18/10, and 9/30/10.  Several major winter storms occurred on 
12/9/09, February 5-6 and February 9-10.  The February storms were snowfall events, 
and snowmelt was distributed over a period of time, which attenuated the flood 
events.   The largest daily rainfall total of 7.04 cm of precipitation occurred on 
August 18, 2010.   The largest snow event occurred on February 6, 2010, with a total 
of 8 cm of water equivalents of snowfall. Storm flow hydrographs were generated by 
storm events throughout the year, with the largest events occurring in late summer 
and winter periods (Figure 9). 
3.1.2. Topography and grain size distribution at Site 1 
The movement of water between the floodplain and the stream channel is 
facilitated by both topography and the permeability of the sediment.  Therefore, maps 
of a) gravel-bar and floodplain topography and b) of the spatial distributions of 
surface grain size were constructed for Site 1.  This upstream study site contains two 
gravel bars that have been accreted into the floodplain.  A simplified version of Site 1 
topography is shown in Figure 6.  This map of the topographic surface shows the 
distribution of topography relative to the stream channel as well as the locations of 
piezometers and chute channels.  Piezometers are distributed along eight transects 
that extend from the stream channel, across the accreted gravel bars and into the 
higher level floodplain are also shown on this map (Figure 6; Illustration 1).   Surface 
topography controls stream flow advection onto the floodplain.  Streamflow could be 
transported onto the floodplain in two distinct ways: overbank flooding directly onto 
 
 25 
 
the floodplain and via a chute channel that occupies the space between the two 
accreted gravel bars (Figure 6).  The main chute channel flows from the stream onto 
the floodplain and then reenters the stream slightly downstream of the study site.  
This chute channel (Illustration 1) conveys flow into two secondary channels during 
flood events (Illustration 3). The chute channel actively conveyed water onto the 
floodplain at least four times during the period of study. 
 
 
Illustration 1: Photo showing floodplain characteristics of Site 1. (A) Little Paint 
Branch stream channel; (B) immediate floodplain/gravel bar; (C) Primary chute 
channel; (D) Uplands. Photo shows view looking downstream. 
A C 
B 
D 
 
 26 
 
 
Illustration 2: Photo looking down chute channel for Site 1. (A) Little Paint Branch 
stream channel; (B) immediate floodplain/gravel bar; (C) Primary chute channel; (D) 
Uplands. Photo shows view looking downstream. 
 
 
 
A 
C 
B D 
 
 27 
 
 
Illustration 3: Photo showing various channels during storm event on Site 1. (A) Little 
Paint Branch stream channel; (B) secondary chute channel; (C) Primary chute 
channel (D) uplands. Photo taken during a major storm event.  Photo shows cross 
sectional view from uplands towards stream. 
 
3.2. Identification of hydrological units 
Hydrostratigraphic units are defined as a stratigraphic formation or groups of 
formations that have similar hydraulic characteristics (Fetter, 2001).  
Hydrostratigraphic units are usually defined by hydraulic conductivity or grain size 
similarities for heterogeneous alluvial floodplain sediments.   In this section, grain 
size distributions of floodplain and gravel bar materials are presented.  These data are 
used to estimate hydraulic conductivity values and to define hydrostratigraphic units. 
A 
B 
C 
D 
 
 28 
 
3.2.1. Determination of hydraulic conductivity values  
The hydraulic conductivity of floodplain and gravel bar systems often reflects 
underlying stratigraphic characteristics (Rovey, 1990; Rovey and Cherkauer, 1994a, 
b; Rovey and Cherkauer, 1995).  Floodplain hydraulic conductivity is often measured 
in the field or estimated from grain size data for representative samples of identified 
hydrostratigraphic units.  A variety of methods have been used to estimate hydraulic 
conductivity from grain size data.  These methods use mean grain size or a smaller 
size fraction (D10) that is thought to represent equivalent pore sizes (e.g. Hazen, 1892; 
Fetter, 2001).  An alternative method uses the entire grain size distribution rather than 
a single ?representative? grain size (e.g. Alyamani and Sen, 1993).  Both the 
representative method (D10) and the grain size distribution method were used to 
estimate hydraulic conductivity for the sediment in the gravel bars and floodplains at 
the study sites. These methods were compared and were considered to give different 
results when K values estimated by the two methods placed the soil sample in 
different classes (Table 1). These differences occurred for 42 percent of the time of 
the samples tested.  Reference size and hydraulic conductivity classes were based 
from studies presented by Lappala, 1978 and Schwartz et al. 2003 using ranges of 
hydraulic conductivities for unconsolidated sediments (Table 1).  Sediment and soil 
samples were sieved and D10 and D50 values were obtained from grain size 
distribution curves (Figure 10).   Hydraulic conductivity values for the various 
sediments vary over orders of magnitude (Table 2), as would be expected for 
sediment sizes that range from silt to gravel.  Hydraulic conductivity values that were 
estimated by the two grain-sized based methods varied by less than one order of 
 
 29 
 
magnitude, indicating a relatively homogeneous hydrostratigraphic unit. The greatest 
difficulty was with the estimate of hydraulic conductivity for gravel samples, which 
are difficult to measure by in-situ field tests, and are not well-defined by most grain-
size dependent methods.  The value of C for the Hazen method was estimated to be 
120 for the gravel samples.  A value of C for most of the other samples was estimated 
to be 60, because they were fine sands.   Comparison of the two methods suggests 
that the methods diverge significantly for the coarser samples suggesting grain-size 
based estimates of hydraulic conductivity for this site may be improved by calibration 
with in-stiu field tests.  
Table 1: Ranges of hydraulic conductivities of sediment types  
Sediment Class Hydraulic Conductivity K (m/d) 
Sandy silt 1-2 
Fine to medium sand 2-10 
Course sand 10-20 
Fine to medium gravel 20-50 
Course gravel 50-100 
Gravel and cobbles 100-1000  
 
Table 2: Hydraulic conductivities calculated from grain-size analysis 
Gravel Bar 
Piezometer 
D10, 
(mm) 
D50, 
(mm) 
A&S 
K, m/day 
Hazen 
K, m/day 
A2 (0-53 
cm) 0.11 0.25 8.01 
Med. 
Sand 6.27 Med. Sand * 
A2 (53-92 
cm) 0.12 0.50 1.55 
Fine 
Sand 7.46 Med. Sand  
B3 (0-79 
cm) 0.21 0.34 42.47 
Course 
Sand 22.86 Course Sand * 
B3 (80-98 
cm) 0.11 0.23 8.96 
Med. 
Sand 6.27 Med. Sand * 
C1 (0-23 
cm) 0.11 0.28 6.69 
Med. 
Sand 6.27 Med. Sand * 
C1 (24-66 
cm) 0.08 0.25 2.27 
Fine 
Sand 3.32 Fine Sand * 
C2 (0-77 
cm) 0.13 0.27 12.61 
Med. 
Sand 8.76 Med. Sand * 
C2(78-
100cm) 0.10 0.50 0.13 Silt 5.18 Med. Sand  
 
 30 
 
D1 (0-35 
cm) 0.13 0.27 11.09 
Med. 
Sand 8.10 Med. Sand * 
D2 (0-30 
cm) 0.14 0.51 4.19 
Fine 
Sand 10.16 Med. Sand  
D2 (30-60 
cm) 0.20 1.40 6.37 
Med. 
Sand 20.74 Course Sand  
E3 (0-33 
cm) 0.13 0.25 12.20 
Med. 
Sand 8.10 Med. Sand * 
E3 (33-53 
cm) 0.14 1.70 57.88 
Course 
Sand 20.32 Course Sand * 
 
Uplands 
Piezometer 
D10, 
(mm) 
D50, 
(mm) 
A&S 
K, m/day 
Hazen 
K, m/day 
A5 (0-40 
cm) 0.19 3.00 254.2 Gravel 37.41 Course Sand  
A5 (40-52 
cm) 0.20 2.00 54.6 
Course 
Sand 41.47 Course Sand * 
A5 (52-72 
cm) 0.08 0.50 0.27 Silt 3.32 Fine Sand  
A6 (0-34 
cm) 0.06 0.18 1.42 
Fine 
Sand 1.87 Fine Sand * 
B6 (0-38 
cm) 0.19 6.00 
1622.7
2 Gravel 37.43 Course Sand  
B6 (38-64 
cm) 0.09 0.27 3.19 
Fine 
Sand 4.20 Fine Sand * 
B7 (0-36 
cm) 0.06 0.14 2.29 
Fine 
Sand 1.87 Fine Sand * 
B7 (36-61 
cm) 0.09 0.40 0.53 Silt 4.20 Fine Sand  
B7 (61-78 
cm) 0.07 0.40 0.02 Silt 2.54 Fine Sand  
C5 (0-66 
cm) 0.06 0.17 1.62 
Fine 
Sand 1.87 Fine Sand * 
D4 (0-70 
cm) 0.01 0.20 1.39 
Fine 
Sand 0.05 Silt  
D4 (70-93 
cm) 0.14 0.60 1.73 
Fine 
Sand 10.16 Med. Sand  
F4 (0-70 
cm) 0.06 0.18 1.42 
Fine 
Sand 1.87 Fine Sand * 
* indicate same sediment class for both methods.  Bold numbers indicate Hazen C coefficient 
was based off of course sand. 
3.2.2. Spatial distributions of grain size, and hydraulic conductivity values  
The grain size distributions of the gravel bar, floodplain, and chute channel 
samples were heterogeneous with grain sizes that ranged from gravel to silt. The 
gravel bars near the stream channel contain coarse, well-sorted sediment.  The 
 
 31 
 
floodplains further from the active stream are much finer grained sediment and also 
more poorly sorted.  Hydraulic conductivity values estimated from grain size 
distribution data ranged from 0.02 to 1622.72 m/day (table 2).  The Alyamani and 
Sen (1993) method indicated that the highest values of hydraulic conductivity, K, 
were found in and along the chute channel.  Active sediment transport in the channel 
brings in coarse sediment and carries out fine sediment.  Therefore, the chute channel 
had a much higher hydraulic conductivity value for the upper 0-40cm soil layer than 
the other sites.  The gravel bars have a thin layer of gravel at the surface, but the 
subsurface material and the pore spaces are dominantly medium sand.  Most locations 
indicated larger grain sizes at the surface, with the exception of piezometer location 
E3, which has a lower grain size near the surface.  Table 3 summarizes these data and 
indicates that the uplands are dominated by fine sands whereas the gravel bar is 
dominated by medium sands. 
3.2.3. Map of average hydraulic conductivity 
Maps of grain size distribution and hydraulic conductivity were constructed 
using the surface D50 and the hydraulic conductivity values for each of the sampled 
locations based of the Alymani and Sen method, 1993 (Figure 11).  The grain size 
distribution map indicates that the chute channel has the highest D50 values.  Lower 
grain size values are found on both sides of the chute channel.  Excluding the chute 
channel, however, the hydraulic conductivity values decrease from the stream 
towards the uplands. The upland floodplain exhibited homogeneous values of 
hydraulic conductivity ranging from 1 to 2 m/day, which is consistent with the sandy-
silt material found in the floodplain.  The highest values of hydraulic conductivity are 
 
 32 
 
found in the chute channel (> 100 m/day), which represent sandy gravel.  The 
downstream end of the chute channel has K values of 2-50 m/day. The immediate 
gravel bar floodplain area showed fine to medium sand/gravel mixture.  
3.2.4. Cross sectional view of grain size data 
Sediment and soil samples were taken at various depths in the uplands and the 
gravel bar.  These data are shown in Figure 12, which shows the soils to about 1 
meter depths (similar to the elevation of the active channel).  In the upland floodplain 
the grain size is fairly homogeneous with depth.  The gravel bars are composed of 
layers of sand and gravel, which vary from site to site.  Soil profiles indicate that 
grain size and hydraulic conductivity is highest near the surface at most locations, this 
is consistent with the observation that the gravel bars are recent additions to the 
floodplain system and have been accreted on top of and adjacent to pre-existing 
floodplain sediments.  An exception is in transect E, which shows evidence of 
deposition of the sediments over a shallow gravel bar at depth.  
3.3. Seasonal distributions of groundwater heads depicted as both time series 
diagrams and seasonal groundwater equipotential maps  
3.3.1. Groundwater head data  
Groundwater head data were monitored to determine the relationship between 
the stream channel and the floodplain groundwater system at both the accreted gravel 
bar site (1) and the incised channel gravel bar (2).  At the floodplain site, an extensive 
groundwater monitoring network was installed to determine exchanges of flow 
between the channel and the floodplain.  Piezometric head data were also used to 
 
 33 
 
evaluate the effects of the chute channel on local recharge and discharge from the 
adjacent groundwater system.  Total heads in the piezometer networks were 
monitored weekly for the study period July 15th, 2009 to August 19th, 2010.   The 
groundwater data from the two sites will be discussed separately; the most extensive 
analysis is for the upstream site, which is the site of aggradation and attachment of 
gravel bars to the floodplain.   
The groundwater head data have been analyzed and presented three formats:  
a) time series analyses, b) map views, c) cross section views of total head.   The time 
series data were used to identify steady-state time intervals for each season.  Head 
data during these intervals were used to generate equipotential maps and cross 
sectional equipotential diagrams that illustrate steady state heads within the gravel 
bars and adjacent floodplain groundwater.     
3.3.2. Time series data of total head  
Time series of groundwater head data were measured at all transects within 
Site 1.  Transects A, C, and E were selected to illustrate total head time series for 
piezometers installed in the floodplain (Figure 13).  In these time series diagrams, 
selected piezometers are identified by their distance from the stream bank (meters) 
and categorized by location within the floodplain (inset gravel bar, chute channel, and 
uplands).  Extreme high events (12/9/09 and 8/12/10) were removed to show 
seasonality.  At Site 1, total head steadily increased from early fall through spring.  
This increase in total head is primarily associated with the decline in 
evapotranspiration demand.  The spring increase in evapotranspiration demand is 
associated with the observed decline in groundwater levels that began in the spring 
 
 34 
 
(March 13th, 2010) and reached a minimum in the late summer.  In late summer in 
both 2009 and 2010, large-magnitude tropical storms ended the summer decline in 
groundwater levels.  Storm-induced spikes in groundwater levels occur throughout 
the year, but are of varying duration and magnitude.  Maximum groundwater head 
elevations were observed as consequences of large storm events.  The largest storm 
events for which groundwater conditions were monitored were the two largest storm 
events in the period of record: the December 9th, 2009 and the August 12th, 2010 
events.  The groundwater minimum occurred on September 23rd, 2009, a result of 
cumulative evapotranspiration demand over the summer months.  
 Although seasonal variations in groundwater heads were observed at all sites, 
the timing and amount of seasonal variation in groundwater head varied with position 
on the transect. Piezometers located in floodplain materials (silts and clays) showed a 
slow increase in head in the fall as evapotranspiration decreased in the late fall into 
the winter months.  These sites also drained slowly as evapotranspiration demand 
increased in the spring and continued into the summer months. This behavior is very 
different than the adjacent sand and gravel bar that maintained much more constant 
groundwater heads over the time period.   The time series data of the gravel bar 
located at Site 2 (transects Z, W, V) responded similarly to the upstream gravel bar 
(Figure 14).  The inset gravel bar at Site 2 showed minor changes in groundwater 
table elevations, which reflect baseflow conditions.   The gravel bar piezometers at 
Site 2 also indicate perturbations associated with the major storms that were observed 
at Site 1    Minor storms were less observable at Site 2 compared with Site 1.  
 
 35 
 
The time series data were used to identify steady state conditions to generate 
equipotential diagrams.  Dates were selected to illustrate: fall (10/14/2009), winter 
(1/13/2010), spring (4/15/2010) and summer (7/21/2010) conditions.  In addition to 
creating equipotential diagrams for each of these steady state conditions, 
equipotential diagrams for two high flow conditions were also generated and 
examined.  The first high flow event was an above-bankfull flood event that occurred 
on 12/9/2009 and the second, a high flow event,  that caused chute channel flow onto 
the floodplain, but did not cause overbank flooding.  This event occurred during a 
tropical storm on 8/12/2010 (Figure 15). 
3.3.3. Seasonal Equipotential Maps  
Equipotential maps of the water surface were constructed for the fall, winter, 
spring, and summer steady state conditions, using groundwater head data (Figure 16). 
Total head values varied less than 0.7 m within the sediment bar-floodplain system 
(head values ranged from 9.14 to 8.45 m).   In summer and fall periods (intervals of 
high evapotranspiration demand; Illustration 4), groundwater elevations were highest 
near the stream and adjacent gravel bar for transects A-C (Figure 17).  During periods 
of low evapotranspirative demand (winter and spring), the highest total head values 
were associated with the higher elevations in the floodplain at all transect locations 
(A-D) (Figure 18).  During winter and spring conditions, the lowest head values were 
located at sites within transects with low topographic elevations, similar to stream 
water surface values.  
 
 
 
 36 
 
 
 
 
  
 
 
The maps of groundwater equipotential values and associated groundwater 
flow directions (Figure 17) indicate that groundwater flows from Little Paint Branch 
into the floodplain for both the fall and summer seasons.  During this time of year, 
piezometric heads are low in the floodplain, therefore water flow directions are from 
the stream into the adjacent gravel bar and then into the finer-grained floodplain.  The 
equipotential gradient is opposite of topographic gradient due to the continuous 
source of water from the stream and the continuous sink for groundwater caused by 
evapotranspiration in the floodplain.   The equipotential maps showed that the stream 
water seeped into the floodplain in transects A-C, distributed throughout the 
Illustration 4: Photo showing vegetation at Site 1. (A) gravel bar; (B) Primary 
chute channel (C) uplands. Photo taken during a storm event looking down the 
chute channel.   
A 
C 
B 
 
 37 
 
floodplain, and drained into the chute channel and back into the stream near transects 
D and E. 
The equipotential maps for winter and spring conditions indicate that the 
groundwater flowed from the floodplain towards the stream.  The floodplain during 
the winter and spring (Figure 18) months is recharged by precipitation and local 
runoff, during periods when evapotranspiration is low.  This results in groundwater 
equipotential maps that follow the topography, with some modification due to the 
variations in hydraulic conductivity in the floodplain, particularly along the chute 
channel.   Groundwater at the north end of the floodplain flowed sub-parallel to the 
stream seeped into the stream at the topographic lows located near the stream at 
transects D and E.  
During all four seasons (Figure 16), a significant component of the flow is 
sub-parallel to the stream.  The source of flow, however, switched from the uplands 
in the winter and spring, to the stream in the summer and fall.  This resulted in two 
groundwater flow reversals annually.  One reversal occurred between the fall and 
winter seasons and the other occurred between spring and summer. These reversals 
are also observed on the time series diagrams. The source of flow was calculated and 
determined to show a greater quantity of flux for summer and fall with flow from the 
stream rather than flux from the uplands during winter and spring (Figure 19).   
3.3.4. Cross section diagrams 
Cross section views of groundwater potentials were constructed for the 
upstream transects at Site 1 where groundwater equipotential gradients are 
approximately perpendicular to the transects, sub-parallel to the stream.  The steady 
 
 38 
 
state total head data that were used to construct the equipotential diagrams were also 
used to generate cross-sectional views of groundwater potential. These cross section 
views were used to examine the role of the chute channel as a groundwater recharge 
or discharge feature.  Cross section diagrams were created for individual transects of 
the stream-floodplain system for seasonal steady-state conditions, low conditions in 
addition to the tropical storm and winter storm events.  Each diagram shows surface 
topography along transects and the total head data for the four steady state conditions 
and groundwater potential maximum and minimum conditions. At Site 1, transects A, 
C, and E (Figure 20), were examined because they emphasize the role of the chute 
channel that enters upstream of the floodplain site.  Spatially across the floodplain, all 
transect show similar patterns (Figure 21). 
 The cross section equipotential diagrams for Site 1 were summarized as three 
main scenarios.  These scenarios are: 1) flow from stream to floodplain, 2) flow 
potential from floodplain into the stream, and 3) third bowl-shaped condition, which 
demonstrates the influence of the chute channel.  Transects A, B, and E display 
declining slope of potential surface from the stream to floodplain for fall and summer 
seasons.  The majority of transects (7 out of the 8) indicate that groundwater flows 
from the stream to the floodplain in the summer to early fall seasons (Table 3). 
The second scenario flows from the floodplain into the stream, consistently 
occurred at transect F. This was due to the higher elevations at this transect and the 
absence of a gravel bar attached to the floodplain.  At transects A, D, and E, 
groundwater flowed from the floodplain towards the stream during the winter and 
spring months.  The third scenario is a bowl-shaped distribution of groundwater 
 
 39 
 
potentials, with higher values near both the stream and the upland floodplain. This 
scenario displays the role of the chute channel in distributing flow.  This scenario is 
observed most prominently at transect C, which received flow from both the upland 
and the gravel bar.  Flow was routed down the chute towards the stream channel or 
towards other sinks during fall, winter, and spring conditions.  Transects B and G also 
showed this distribution of groundwater potential in winter and spring (Table 3). 
Table 3: Three scenarios observed in Site 1 cross section equipotential diagrams 
Seasons 1: Stream to floodplain 2. Floodplain to stream 3: Bowl-shaped 
Fall A, B, E F C, D 
Winter H A, D, E, F B, C, G 
Spring  A ,D, E, F, H B, C, G 
Summer A,B, C, D, E, G, H F  
 
The potential surfaces illustrated in both the map and cross section views 
indicate seasonal reversals in flow due primarily to seasonal variations in 
groundwater levels in the upland floodplain.  This is likely caused by two processes, 
seasonal variations in evapotranspiration rates and lag times in piezometric responses 
between the coarse grained gravel bar and the fine-grained floodplain.  These grain 
size-based characteristics were examined in the previous section. 
3.4. Probability distribution of groundwater heads 
Groundwater head data also provide information on the depth to the 
groundwater table at the site.  Many models of floodplain ecological functions are 
based on inundation times or the amount of time that the floodplain sediments are 
saturated (Junk et al. 1989).  Groundwater probability diagrams were constructed for 
the groundwater data at each of the transect locations.  These data are plotted as the 
percent of time that the groundwater table is at or above a given depth relative to the 
 
 40 
 
ground surface (Figure 22).   For Transect A, the groundwater reached the ground 
surface 2% of the time at the gravel bar adjacent to the channel (piezometer A3)  and 
12% of the time in the chute channel (piezometer A5).   Depth of flow in the chute 
channel was greater than 0.55 meters 2% of the time, consistent with overbank 
flooding on both the gravel bar and in the chute channel.  At transect C, the 
groundwater reached the surface of the chute channel 14% of the time (piezometer 
C4). The groundwater table was always below the ground surface for the upland 
floodplain piezometers, but the water table approached the surface (0.4-0.2 m) 2% of 
the time for many of the upland floodplain sites within the study reach.  For the 
upland floodplain, most of these high water tables occurred in the winter and early 
spring.  Due to the lower topography at transect E, the gravel bar was flooded 3% of 
the time  to depths of 0.1 m, however, the chute channel and upland piezometers for 
transect E indicated that the water table never reached the surface, although the chute 
channel was within 0.1 m of the surface 2% of the time.  In summary, for this 
floodplain groundwater system the water table is closest to the surface in the coarse 
grained portions of the reach.  Due to the high hydraulic conductivities, however, the 
water table maintains saturated conditions only for short periods. The finer-grained 
upland floodplain had lower groundwater elevations for most of the summer season.  
Groundwater tables were closest to the surface during the non-growing season, when 
evapotranspirative demand was lowest.  
 
 
 41 
 
3.5. Piezometric and stream responses to storm events  
Equipotential maps were also constructed for the maximum of the transient 
groundwater conditions associated with the two major storm events (December 9th, 
2009 and August 12th, 2010; Figure 23).  The December 9th, 2009 event occurred 
when groundwater tables were high and flow was from the floodplain towards the 
stream channel.  This event caused overbank flooding and it generated the highest 
equipotential values.  This storm activated the chute channel and the major flow 
direction was sub-parallel flow to the stream direction.  Groundwater discharged into 
the stream near transects E and F.  
  The other major storm that was monitored was a late summer tropical storm 
on August 12th, 2010.  This storm occurred near the groundwater and baseflow 
minimum.  This tropical storm did not generate overbank flooding, but water flowed 
into the chute channel and seeped into the floodplain at the gravel bar.  The highest 
groundwater heads were at the upstream end of the reach and localized at the stream 
bank.  The highest single point groundwater elevation was in the chute channel.  This 
high flow event occurred during low groundwater conditions, which caused recharge 
from the chute channel into the adjacent gravel bar and floodplain groundwater 
system.  Equipotential diagrams generated for the summer groundwater minimum 
also produced groundwater flow patterns that ran parallel to the stream channel.  
Water flowed from the stream channel into the groundwater at the upstream end of 
the reach. 
 
 42 
 
3.5.1. Precipitation from a major tropical storm  
A significant tropical storm occurred on September 29th, 2010 around 10:00 
pm and continued until 10:30 am October 1st, 2010 and produced 6.9 cm of 
precipitation (Figure 24).  The cumulative distribution of precipitation is shown in 
(Figure 25), which was constructed with 15 minute interval data.  There were four 
main distinct peaks in storm precipitation at 60, 270, 735, and 1,350 minutes into the 
storm. The center of mass of rainfall, centroid, occurred approximately at the 710th 
minute with a value of 3.5cm (Figure 26). The average rainfall intensity was 
0.71?1.17 cm/min. The storm occurred in several bursts, as indicated in Figure 26. 
3.5.2. Floodplain piezometric response to the tropical storm  
The groundwater heads were monitored during and after the storm.  As shown 
in the photograph (Illustration 3), the chute channel at peak flow had a similar peak 
gauge height as the main stream channel.  Therefore, in the evaluation of piezometric 
response to the storm event, groundwater time series graphs were constructed for the 
recession limb of the hydrograph.  The groundwater recession curves were compared 
with the recession curve for the chute channel shown in blue. Groundwater time 
series graphs were constructed for the recession limb of the hydrograph.  These 
graphs are shown for transects A, C, and E in figure 27.  
 
 43 
 
 Illustration 3: Photo showing various channels during storm event on Site 1. (A) Little 
Paint Branch stream channel; (B) secondary chute channel; (C) Primary chute 
channel (D) uplands. Photo taken during a major storm event.   
 
 The response of the shallow groundwater to the storm event varied with 
sediment type and position along the floodplain.  At the two upstream transects, the 
groundwater table in the gravel bar responded differently from the upland floodplain 
due to both position and hydraulic conductivity.  At transects A and C, the gravel bar 
piezometers responded similarly.  The gravel bar piezometers had lower heads than 
the adjacent chute channel, but had similar recession curves to the chute channel.  At 
transects A and C, the chute channel level remains higher than the gravel bar 
piezometers throughout the recession limb of the hydrographs. The adjacent fine-
A 
B 
C 
D 
 
 44 
 
grained floodplain responded more slowly to water inputs than the gravel bar, but 
floodplain total heads eventually were higher than both the chute channel and gravel 
bar (Figure 25).  This increase in head in the fine-grained floodplain occurred as a 
response to flooding of the chute channel.  The rapid rise of the upland floodplain 
piezometers may be due to the capillary fringe response, or due to the relatively low 
specific yields of these finer-grained sediments. The delayed response of upland 
piezometers confirms the lower hydraulic conductivity assigned to these sediments in 
the upland floodplains.  The upland floodplain piezometers on all transects showed a 
peak at 210 minutes after the storm started, this is significantly later than the peak in 
the chute channel and adjacent gravel bar.  At transect E, the chute channel and the 
gravel bar are both less distinct features, the gravel bar has significantly lower surface 
sediment sizes than the upstream gravel bar.  The piezometric responses at this 
location could be due to dissipation of flow from the chute channel into the 
surrounding region, which recharges the groundwater.   
 One interesting aspect of these time series diagrams is that the flow reversal 
observed between the upland floodplain and the gravel bar occurs during the 
recession limb of a major storm.  The seasonal reversal in flow between the upland 
floodplain and the stream channel gravel bar segments appear to be initiated by the 
large tropical storms described here.  
 
 45 
 
4. Discussion  
The major controls on exchanges of water between floodplains and stream 
channels include floodplain and channel topography, groundwater head values and 
gradients, and the distribution of hydraulic conductivity in both the floodplain an 
regionally if the site is not bounded by fine-grained sediment (Woessner, 2000).  
Little Paint Branch site is characterized by spatial variability in topography and grain 
size resulting in heterogeneous hydraulic properties (Miall, 1996; Kollet et al., 2002). 
The floodplain and stream are underlain by very compact fine clay that limits 
hyporheic exchange under the stream, but facilitates exchanges within the shallow 
surface sediment.  Wroblicky et al. (1998), identified floodplain and riverbed 
heterogeneity as a major control on floodplain-channel exchange.  The recently 
deposited gravel bars (Blanchet, 2009) are significant hydrologic features of the 
channel-floodplain sediment and provide heterogeneity of hydraulic conductivity with 
n the floodplain system. 
4.1. Effects of channel morphology on floodplain-channel characteristics 
In this study, the channel and floodplain morphology along with sediment 
characteristics influenced exchanges of water between the channel and the floodplain 
exchanges.  The bar formation along the channel created low bank elevations that 
facilitated overbank flooding.  Along the gravel bar, fine-grained floodplain 
boundary, fine-grained sediment transport maintains a chute channel that brings 
streamflow onto the floodplain.  These chute channels are found at the gravel-fine 
sediment transition along all of the gravel bars in this portion of Little Paint Branch.  
Examination of the site during flood events, however, indicated that chute channels 
 
 46 
 
play a significant role in bringing water onto the floodplain.  The chute channel 
carries streamflow onto the floodplain even when overbank flooding does not occur. 
In the incised reach, formation of a chute channel along the edge of the gravel bar 
only serves to further isolate the gravel bar from the floodplain.  Within incised 
reaches, groundwater elevations in the floodplain constantly drain towards the stream 
flow, indicating a gaining stream with a loosing floodplain (Tucci and Hileman 
1992).  This drainage alters the normal connectivity between the floodplain and 
stream channel (Kroes and Hupp 2007).  Isolation of the floodplain from stream 
floodplain interactions and water level fluctuation is detrimental (Kwak, 1988; King 
and Grant, 1996).  In addition to vegetation complications, Groffman et al. (2002) 
observed that lower water tables within floodplains of incised streams result in the 
inability of saturated soils to offer potential for denitrification and biological uptake 
of nitrate (Burt et al., 1999; Hill, 1996; Gilliam, 1994). 
 The natural aggradation at Site 1 resulted in complex floodplain features such as 
attached gravel bars and chute channels that influenced groundwater levels and thus 
active floodplain vegetation and biota. This natural re-attachment processes occurred 
due to streambed aggradation and thus without disruption of floodplain vegetation.  
Complex, vegetated floodplain can serve multiple functions, including buffering 
streams against pollution (Burt et al., 1999; Schultz et al., 2000; Lee et al., 2000), 
facilitating exchanges between surface and groundwater, and reducing stream bank 
erosion (Micheli and Kirchner, 2002; Schultz et al., 2000; Palone and Todd, 1997). 
Site 2 shows a direct disconnection with its associated floodplain.  This is common 
 
 47 
 
for incised streams that are hydrologically disconnected from their floodplains 
(Schilling, 2004).   
 
4.2. Importance of chute channels 
Chute channels along the boundary between the gravel bar and the floodplain 
and were observed throughout the larger study reach, including the incised reach.  
Where channels are not incised, the chute channels play a significant role in bringing 
water onto the floodplain and recharging local groundwater levels In this study, this 
role is demonstrated through use time series diagrams during storm vents, cross 
section diagrams of high flow conditions and equipotential maps of high flow 
conditions.   The time series diagrams indicate the rapid response of the gravel bars to 
streamflow events, but they also show that the chute channel is influential in bringing 
water into the less conductive upland side of the chute channel.  Groundwater heads 
indicate that flow moves from the chute channel into the floodplain during both 
summer and winter storm flow conditions.  The chute channel also appears to 
function as a stable point for groundwater levels within the floodplain and maintains 
similar levels throughout the year.  Lastly, the effect of the chute channel decreases 
downstream as grain size decreases and size of the chute channel decreases 
downstream.  This allows more water to be distributed within the floodplain before 
exiting and returning to the stream channel. Previous studies have shown that chute 
channel features and bar topography can alter hyporheic flux rates and patterns 
(Harvey and Bencala, 1993; Wondzell and Swanson, 1999; Kasahara and Wondzell, 
2003; Anderson et al., 2005; Gooseff et al., 2006a,b; Poole et al., 2006). In this study, 
 
 48 
 
the chute and bar topography facilitates horizontal exchanges between the channel 
and floodplain.  
Results from this study also support other studies citing floodplain 
geomorphological characteristics as significant influence on flow dynamics 
(Wondzell and Swanson, 1999; Kasahara and Wondzell, 2003).  In addition, similar 
results were found in hydrogeologic modelling experiments preformed by Kasahara 
and Wondzell (2003) and Poole et al. (2006), which suggests that the surface 
hydrology of floodplain channels can create temporally dynamic variations that 
deviate significantly from the steady state hydraulic gradients within alluvial aquifers 
(Woessner, 2000) altering groundwater elevations and flow directions among 
seasons. 
4.3. Groundwater reversal-seasonal variations 
Seasonal variations in groundwater tables are can be caused by seasonal 
variations in precipitation, precipitation intensity, and evapotranspiration.  In the mid-
Atlantic United States, precipitation is not seasonal, but variations in precipitation 
intensity do occur (Winter, 1994) and variations in evapotranspiration are very 
significant. Seasonal variations were observed in both time series graphs of 
groundwater potential and in sequential stead-state maps of the groundwater system.  
The reversal of groundwater flow occurred twice a year.  Flow moved from the 
channel into the floodplain in the summer.  This flow reversed in the fall, and the 
reversal occurred rapidly, induced by tropical storms that caused an increase in 
groundwater heads in the uplands.  The second reversal occurred in the spring, 
(March-April, shortly after leaf-out occurred). These seasonal variations in water 
 
 49 
 
levels associated with evapotranspiration changes drives many of the exchanges 
between the floodplain and the stream channel. 
Although the seasonal variations were observed at all transects, the timing and 
the amount of seasonal variation in groundwater head varied with position within 
transects.  The piezometers installed in the floodplain filled up slowly as 
evapotranspiration decreased but also drained slowly as evapotranspiration demand 
increased in the spring and continued into the summer months.  This difference in 
response of the piezometers is likely caused by both their position on the floodplain 
and hydraulic conductivity. Middle piezometers exhibited lower elevations for both 
winter and spring seasons, suggesting that the chute channel did not supply water to 
the floodplain for most of these channels.  During high storm events, piezometers in 
the chute channel are more likely to have surface and over top flow compared to 
piezometers in the floodplain and uplands. Seasonal variation and spatial results are 
similar to that observed within other systems with strong seasonal variations in 
evapotranspiration or seasonal precipitation (Hill, 1990; Waddington et al., 1993; 
Squillace, 1996; Burt, 1997).   
Field data indicate that focused recharge of the floodplain occurs along the 
upstream edge of the gravel bar for summer and fall months.  Chute channels can 
initiate transient groundwater mounds and enhanced seepage rates.   Although 
hydrological flow paths in near-stream floodplain zones can be intricate, owing to a 
variety of groundwater sources such as inflow from uplands, urban runoff, upwelling 
from deeper strata, bank storage, overbank inundation, etc. (Hill, 1990; Squillace, 
1996; Cey et al., 1999; Clement et al., 2003), the net effect of converging 
 
 50 
 
groundwater flow paths in the floodplain results in seasonally or perennially saturated 
conditions. 
4.4. Soil hydraulic conductivity estimates  
Hydraulic conductivity was estimated from grain-size measurements.  These 
techniques tend to give higher averages with lower variances than in-situ 
measurements that incorporate other hydraulic characteristics of the soils (Eggleston 
and Rojstacze, 2001). In this study, grain size was used to separate the coarse grained 
sediment of the gravel bar from the fine-grained sediments of the floodplain.  
Although previous studies indicate that  grain size estimates of hydraulic conductivity 
often do not correspond well to field measured hydraulic conductivity for fine-
grained sediments, they perform better for sand-sized and other coarse grained 
sediments, such as on the gravel bars.  Both the grain size-based estimates of 
hydraulic conductivity and the observed piezometric responses indicate that the 
upland floodplain has significantly lower hydraulic conductivity and lower specific 
yields than the adjacent gravel bars.  Studies have shown that field measures are 
generally greater than or similar to laboratory analysis in which laboratory analyses 
underestimated the hydraulic conductivity (Taylor et al., 1987; Herzog et al., 1989; 
Fetter, 2001).  
4.5. Limitations 
Studies of dynamic processes in heterogeneous materials are often limited by 
the available data.  This study was motivated, in part, by a need to understand the 
 
 51 
 
major processes that influence water exchanges between floodplains and stream 
channels.  Identification of these processes can then guide future field work. 
Two types of limitations were present in this study: site limitations and 
modeling approach. Groundwater monitoring requires arrays of piezometers that 
increase in complexity with the size and both geomorphic and sediment heterogeneity 
of field sites.  Mapped results are influenced by the lack of piezometers in floodplain 
locations at Site 2.  Piezometers at further distances from the stream at Site 1 would 
be useful do determine flow from the upland towards the channel.  In addition, 
continuous monitoring of piezometers (versus once a week) would have produced 
more accurate results for the unique events such as storm or drought events,. 
In this study, equipotential diagrams were created in GIS rather than in 
MODFLOW or other modeling programs, which only recently have been adapted to 
shallow groundwater and wetland environments.  Equipotential diagrams in all these 
models are commonly determined by Kriging.  This option is available in GIS and 
was used to construct the equipotential maps.  In some cases, (particularly with the 
chute channel data) over-smoothing can be identified as a limitation. Despite this 
limitation, kriging offered less restrictions of mapping the groundwater compared to 
other interpolation models such as inverse distance weighted interpolation. 
In addition, model predictions are limited by the geohydrological data for the 
study site. It was assumed that horizontal flux would dominate because the sediment 
layers within the aquifer are horizontally continuous and a shallow confining layer is 
found throughout the study site. Groundwater equipotential flow maps were produced 
strictly with use of the hydraulic head values obtained from field data. 
 
 52 
 
Although this project focused on defining surfacewater- groundwater 
interactions and identifying seasonal variations in groundwater floodplain patterns, 
these data could be used in future research as part of a floodplain mass balance 
model.  This would include measurements of evapotranspiration, stream discharge, 
precipitation directly at the site, and urban runoff to complete a proper mass balance 
of the site to determine the groundwater input to and from the stream.  
 
 
 53 
 
5. Conclusion  
Measurement of hydrological processes in a small urban floodplain revealed a 
complex interaction between streams and groundwater systems. Exchanges of 
floodplain groundwater with streamflow were initiated by changes in streamflow and 
evapotranspiration. Three zones were established within the Site 1 floodplain, having 
common heads and sub-parallel flow.  Local surfacewater circulation in the 
underlying sediments created areas of groundwater recharge and discharge 
characterized by gaining and losing stream sections. This emphasizes the importance 
of characterizing surfacewater-groundwater exchange at the floodplain and channel 
scale and determined the seasonal, location, and magnitude of the interactions within 
a small scale. Future studies should use these results to develop a monitoring network 
to examine exchange processes in large segments of the floodplain.  This research 
suggests that these studies should be conducted over an annual cycle.  Piezometers 
should be installed to document the effects of sediment heterogeneity, and to monitor 
the effects of chute channels on floodplain groundwater. 
It is important to note that the reversal in groundwater flow directions from 
the channel into the floodplain is facilitated by the hydraulic conductivity of the 
sediment, but also the high evapotranspiration rates of the mature forest that is 
growing in the floodplain.  This forest canopy would be significantly disturbed by 
?cutting down the floodplain?.  This suggests that channel aggradation methods might 
provide an alternative restoration technique. 
 
 
 54 
 
Appendices A-Figures 
 Figure 1:  Conceptual diagram showing floodplain and channel of near channel 
surface and subsurface features and active exchange of groundwater-surfacewater 
(NRC, 2002) 
 
 
Figure 2: Gaining and losing stream conceptual diagrams showing groundwater flow 
direction from a stream (Winter, 1998).  
 
 
 55 
 
upland
Floodplain
A A?
B B?
BFA A?
Gravel bars attached to floodplain
BF
Bankfull channel and gravel bars
Inset into floodplain
B
B?
clay silt sand gravel
 
 
Figure 3:  Conceptualization of differences between Little Paint Branch floodplains, 
A- an attached active floodplain with sediment bars; and B- incised stream with 
sediment bars incised into floodplain. BF represents baseflow.  
 
 
 56 
 
LITTLE PAINT 
BRANCH
Site 2
Site 1
  
Figure 4:  Study site of intact floodplain along Little Paint Branch, upstream of the 
junction with Paint Branch.  Blue polygons indicate the sites within Little Paint 
Branch.  
 
 
 57 
 
  
Figure 5: A. Upstream study site showing gravel bars accreting onto floodplain (a), 
chute channel (b), and a mid-channel gravel bar (c); B. Downstream site on sediment 
bar incised into floodplain. 
 
 
A B 
c 
b 
a 
 
 58 
 
 Figure 6: Topography of the floodplain adjacent to the stream channel at Site 1. The 
study site consists of a gravel bar that has accreted onto the floodplain (D1, E1) and a 
chute channel that runs parallel and splits off into 3 directions.   
 
 
 59 
 
0
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Date
Ra
inf
all
, c
m
 Figure 7:  Daily precipitation from the Beltsville gauge for the study period. Average 
precipitation during July 1st to October 4th was 0.22?0.62 cm. 
Cumulative Hyetograph
0
20
40
60
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100
7/1
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 Figure 8: Cumulative precipitation for the Beltsville Gauge over the study period.  
Total precipitation during July 1st to October 4th was 98 cm. 
 
 60 
 
0
2
4
6
8
10
12
6/26/2009 10/4/2009 1/12/2010 4/22/2010 7/31/2010
Di
sc
har
ge,
 m
3/s
 
Figure 9: Daily average discharge in Little Paint Branch for the study period.  Note 
seasonal increases in baseflow and the relative magnitudes of the winter and summer 
floods. 
 
 61 
 
 
 
Gravel Bar and Chute Channel
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.01 0.1 1 10 100
Grain Size (mm)
Cu
mu
lat
ive
 pe
rce
nt 
(%
)
A2(0-53cm)
A2(54-92cm)
B3(0-79cm)
B3(80-98cm)
C1(0-23cm)
C1 (24-66cm)
C2(0-77cm)
C2(78-100cm)
D2 (0-30cm)
D2(30-60cm)
E3(0-33cm)
E3(34-54)
A5(0-40cm)
A5(40-52cm)
A5(52-72cm)
Uplands
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.01 0.1 1 10 100
Grain Size (mm)
Cu
mu
lat
ive
 pe
rce
nt 
(%)
A6(0-34cm)
B6(0-38cm)
B6(38-64cm)
B7(0-36cm)
B7(61-78cm)
C5(0-66cm)
D4(0-70cm)
D4(70-93cm)
F4(0-70)
Figure 10: Soil profiles used to estimate D10 and D50 values. Top: Gravel Bar 
(Piezometers: A2, B3, C1, C2, D2, E3) and chute channel piezometers (A5). 
Bottom: Uplands (Piezometers: A6, B6, B7, C5, D4, F4). Samples sorted by 
colors. Solid line is for top core; dotted lines deeper in core samples for that 
piezometer. Legend displays piezometer and depth of soil core sample. 
 
 
 62 
 
 
Figure 11: Hydraulic conductivity values and average D50 values for Site 1 
piezometers.  
 
 
 
 63 
 
Gravel Bar Soil Profile
0
20
40
60
80
100
120
A2 B3 C1 C2 D1 D2 E3
Piezometers
De
pth
s f
rom
 su
rfa
ce
, c
m
Fine silt
Sandy Silt
Fine to
medium
sand
Coarse
sand
Fine to
medium
gravel
Coarse
gravel
Uplands Soil Profile
0
20
40
60
80
100
120
A5 A6 B6 B7 C5 D4 F4
Piezometers
De
pths
 fr
om
 sur
fac
e, c
m
Fine silt
Sandy
Silt
Silt
Fine to
medium
gravel
Gravel/
Cobbles
 Figure 12: Soil profile for Site 1- (A) floodplain soil profiles; (B) upland soil 
profiles.  Average surface elevation at (A): 9.602 meters. Average surface elevation at 
(B): 9.301 meters. 
 
 64 
 
 
8.3
8.5
8.7
8.9
9.1
9.3
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
Date
To
tal
 he
ad
, m 1.5
5.9
10.4
15.2
19.8
25.9
30.9
8.3
8.5
8.7
8.9
9.1
9.3
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
Date
To
tal
 he
ad
, m
1.2
7.8
12
17.3
28
34
8.3
8.5
8.7
8.9
9.1
9.3
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
Date
To
tal
 he
ad
, m
2.5
7.3
11.8
18.3
23.4
29.7
35
Figure 13:  Transect time series (Top) Transect A; (Middle) Transect C; (Bottom) Transect E. 
Red lines represent accreting gravel bar piezometers; Blue lines represent chute channel 
piezometers; Black dotted lines represent uplands piezometers. Legend indicates distance from 
stream in meters for each piezometer. Major storm event were removed to show seasonality.  
 
 
 65 
 
5.4
5.6
5.8
6.0
6.2
6.4
6.6
6.8
7.0
7/1
5/0
9
8/1
5/0
9
9/1
5/0
9
10
/15
/09
11
/15
/09
12
/15
/09
1/1
5/1
0
2/1
5/1
0
3/1
5/1
0
4/1
5/1
0
5/1
5/1
0
6/1
5/1
0
7/1
5/1
0
Date
To
tal
 he
ad
, m
2 (Z)
10 (Z)
14.3 (Y)
16.4 (X)
5.35(W)
10 (W)
1 (V)
6 (V)
 
Figure 14: Site 2 time series of water level elevations showing transects and distance 
from the stream in legend (meters).  Colors indicated transect; Dotted lines back 
transects farther in gravel bar; Solid lines are piezometers closest to stream.  
 
 66 
 
 
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m
1.5
5.9
10.4
15.2
19.8
25.9
30.9
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m
1.2
7.8
12.0
17.3
28.0
34.0
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m
2.5
7.3
11.8
18.3
23.4
29.7
35.0
Figure 15: Complete time series (Top) Transect A; (Middle) Transect C; (Bottom) 
Transect E. Red lines inset gravel bar piezometers; Blue line chute channel 
piezometers; Black dotted lines are upland piezometers. Legend indicates distance 
from stream in meters for each piezometer. Peaks indicate major storm events. 
 
 
 67 
 
 
Figure 16: Site 1 equipotential maps for each season.  Low to high elevations are 
represented by light to dark blue shading and thin to thick contours lines respectively. 
Top left, Fall; Top right, Winter; Bottom left, Spring; Bottom Right, summer. 
 
 68 
 
 
Figure 17: Enlarged equipotential maps of (Top) summer and (Bottom) fall.  Low to 
high elevations are represented by light to dark blue shading and thin to thick 
contours lines respectively. 
 
 69 
 
 
Figure 18: Enlarged equipotential maps of (Top) winter and (Bottom) spring. Low to 
high elevations are represented by light to dark blue shading and thin to thick 
contours lines respectively. 
 
 70 
 
 
 
-10.0
0.0
10.0
20.0
30.0
40.0
Winter Spring Summer FallG
ro
un
dw
ate
r F
lux
, m
3/d
ay
 
Figure 19: Seasonal groundwater flux graph. Shows Figure 17/18 dark blue area 
with orange arrows flux rates seasonally. 
 
 71 
 
 
Transect A
7
7.5
8
8.5
9
9.5
10
10.5
11
0 5 10 15 19 23 27 31 35 39 44
Distance (m)
El
ev
ati
on
 (m
)
Transect C
7
7.5
8
8.5
9
9.5
10
10.5
11
0 5 10 15 19 23 28 32 37 42 47
Distance (m)
El
ev
ati
on
 (m
)
Topography
Fall
Winter High
Winter
Spring
Summer
Low
Summer
High
Figure 20: Groundwater elevation plots for transect A, C, and E.  
 
Transect E
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
0 5 10 14 18 22 25 30 34 39 44
Distance (m)
Ele
va
tio
n (
m)
??Head  
 
 72 
 
 
Figure 21: Seasonal difference in groundwater elevations. Dark blue 
indicates largest change; light blue shows smallest changes in elevation 
between seasons.  
 
 73 
 
 
Figure 22: Annual flow duration curves (Top) A transect; (Middle) C transect; 
(Bottom) E transect. Solid black thick line indicates surface level.  
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 10 20 30 40 50 60 70 80 90 100
% time water is at or above indicated value
De
pth
 to
 w
ate
r, m
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 10 20 30 40 50 60 70 80 90 100
% time water is at or above indicated value
De
pth
 to
 w
ate
r, m
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 10 20 30 40 50 60 70 80 90 100
% time water is at or above indicated value
De
pth
 to
 w
ate
r, m
GRAVEL BAR
CHUTE CHANNEL
UPLANDS
 
 74 
 
 
Figure 23: Site 1 equipotential maps of highs and lows conditions.  Top left, Low; 
Top right, High snow; Bottom, High rain. Low to high elevations are represented by 
light to dark blue shading and thin to thick contours lines respectively.  
 
 75 
 
Storm Precipitation
0
1
2
3
4
5
6
7
9/2
6/1
0
9/2
7/1
0
9/2
8/1
0
9/2
9/1
0
9/3
0/1
0
10
/1/
10
Date
Ra
inf
all
 (c
m)
 Figure 24: Time series of fall tropical storm from September 29th, 2010 to October 
1st, 2010 taken from Beltsville gauge.  
 
Hydrograph- Rainfall during Fall storm
0
0.1
0.2
0.3
0.4
0.5
0.6
0 500 1000 1500 2000 2500 3000 3500 4000
Time since storm began, mins
Pr
ec
ipi
tat
ion
 (c
m)
 pe
r 1
5 m
in 
int
erv
als
 Figure 25: Detailed time plot of fall tropical storm from September 29th, 2010 to 
October 1st, 2010 in 15 minute intervals.  
 
 
 76 
 
Hyetograph-Cumulative Precipitation for Fall Storm (total 6.9 cm)
0
1
2
3
4
5
6
7
8
0 500 1000 1500 2000 2500 3000 3500 4000
Time since storm began, mins
Pr
ec
ipi
tat
ion
, to
tal
, c
m
 Figure 26: Hyetographs distribution of rainfall with time shows the largest peak 
occurring at the 270th minute containing 0.508 cm of precipitation.  
 
 
 
 
 77 
 
 
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
0 210 1098 1308 1530 2568 2880 4140
Minutes from start of data collection
Gr
ou
nd
wa
ter
 E
lev
ati
on
s (
m)
1.5
5.9
10.4
15.2
19.8
25.9
30.9
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
0 210 1098 1308 1530 2568 2880 4140
Minutes from start of data collection
Gr
ou
nd
wa
ter
 E
lev
ati
on
s (
m)
1.2
7.8
12.0
17.3
28.0
34.0
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
0 210 1098 1308 1530 2568 2880 4140
Minutes from start of data collection
Gr
ou
nd
wa
ter
 E
lev
ati
on
s (
m)
2.5
7.3
11.8
18.3
23.4
29.7
35.0
Figure 27: (Top) Transect A; (Middle) Transect C; (Bottom) Transect E time series graphs 
during the tropical storm on September 29th, 2010. Red lines are accreting gravel bar 
piezometers; Blue line are chute channel piezometers; Black dotted lines are uplands 
piezometers. Distance from stream labeled in legend.  
 
 78 
 
Appendices B-Additional Figures not used in text. 
 
 
Transect B
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m
1.0
6.3
11.0
16.0
21.2
26.0
29.6
34.6
Transect D
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m
8.3
14.5
20.0
30.9
37.0
Transect F
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m
2.7
6.4
11.4
16.1
A1: Extra complete time series- (Red lines inset gravel bar piezometers; Blue line 
chute channel piezometers; Black dotted lines are upland piezometers.  
 
 79 
 
 
  
 
 
Transect G
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m 1.7
7.8
11.1
Transect H
8.1
8.3
8.5
8.7
8.9
9.1
9.3
9.5
9.7
7/1
5/2
00
9
8/1
5/2
00
9
9/1
5/2
00
9
10
/15
/20
09
11
/15
/20
09
12
/15
/20
09
1/1
5/2
01
0
2/1
5/2
01
0
3/1
5/2
01
0
4/1
5/2
01
0
5/1
5/2
01
0
6/1
5/2
01
0
7/1
5/2
01
0
8/1
5/2
01
0
Date
To
tal
 he
ad
, m 2.4
7.0
A2: Extra complete time series- (Red lines inset gravel bar piezometers; Blue 
line chute channel piezometers; Black dotted lines are upland piezometers.  
 
 
 80 
 
 
Transect B
7
7.5
8
8.5
9
9.5
10
10.5
11
0 5 10 15 20 24 29 34 38 43 47
Distance (m)
El
ev
ati
on
 (m
)
Topography
Fall
Winter High
Winter
Spring
Summer
Low
Summer
High
Transect D
7
7.5
8
8.5
9
9.5
10
10.5
11
0 5 10 15 20 24 29 34 38 42
Distance (m)
El
ev
ati
on
 (m
)
Topography
Fall
Winter High
Winter
Spring
Summer
Low
Summer
High
Transect F
7
7.5
8
8.5
9
9.5
10
10.5
11
0 4 8 13 17
Distance (m)
El
ev
ati
on
 (m
)
Topography
Fall
Winter High
Winter
Spring
Summer
Low
Summer
High
A3: Extra Groundwater elevation plots. 
 
 
 81 
 
  
 
 
 
 
 
Transect G
7
7.5
8
8.5
9
9.5
10
10.5
11
0 4 7 11
Distance (m)
El
ev
ati
on
 (m
)
Topography
Spring
Summer
Low
Summer
High
Transect H
7
7.5
8
8.5
9
9.5
10
10.5
11
0 4 8
Distance (m)
El
ev
ati
on
 (m
)
Topography
Spring
Summer
Low
Summer
High
A4: Extra Groundwater elevation plots. 
 
 
 82 
 
 
 
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
0 20 40 60 80 100
% time water is at or above indicated value
De
pth
 to
 w
ate
r, m
Gravel Bar
Chute Channel
Uplands
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 20 40 60 80 100
% time water is at or above indicated value
De
pth
 to
 w
ate
r, m
A5: Annual flow duration curves (Top) B transect; (Bottom) D transect. Solid 
black thick line indicates surface level. 
 
 83 
 
Appendices C-Data 
 
? Tables below shows data collected for groundwater heads for study period.  
? Site benchmark was 10.  
 
 
 
 
 84 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TRANSECT A    Bank Elevation= 9.34 
Piezometer A1 A2 A2a A3 A4 A5 A6 A7 
Topography Elevation 9.499 9.601 9.601 9.509 9.606 9.149 9.735 9.604 
7/15/2009 8.69 8.765 8.963 8.738 8.745 8.62   
7/22/2009 8.67 8.762 8.963 8.749 8.746 8.548   
7/24/2009 8.727 8.694 8.963 8.791 8.789 8.966   
7/29/2009 8.71 8.783 8.963 8.773 8.764 8.743   
8/5/2009 8.727 8.789 8.963 8.778 8.774 8.816   
8/12/2009 8.646 8.778 8.963 8.758 8.755 8.805   
8/20/2009 8.708 8.773 8.963 8.753 8.758 8.597   
8/27/2009 8.704 8.777 8.963 8.758 8.763 8.754   
9/9/2009 8.74 8.824 8.963 8.809 8.806 8.835   
9/16/2009 8.741 8.81 8.963 8.799 8.797 8.817   
9/23/2009 8.727 8.797 8.963 8.791 8.779 8.708   
9/30/2009 8.739 8.818 8.983 8.81 8.805 8.843   
10/7/2009 8.731 8.808 8.963 8.787 8.782 8.71   
10/14/2009 8.75 8.817 8.973 8.814 8.792 8.648   
10/21/2009 8.758 8.831 8.983 8.885 8.819 9.000   
10/29/2009 8.83 8.921 8.998 8.971 8.936 9.205   
11/4/2009 8.773 8.844 8.987 8.829 8.824 9.013   
11/11/2009 8.773 8.842 8.983 8.84 8.826 9.004   
11/18/2009 8.764 8.84 8.973 8.838 8.825 8.995   
12/2/2009 8.777 8.857 8.963 8.874 8.835 9.03   
12/9/2009 9.31 9.412 9.553 9.459 9.546 9.698   
12/16/2009 8.807 8.908 9.015 8.909 8.874 9.087   
12/30/2009 8.813 8.884 8.987 8.912 8.877 9.084   
1/6/2010 8.784 8.869 8.963 8.858 8.837 9.058 9.082 9.115 
1/13/2010 8.664 8.762 8.963 8.837 8.824 8.986 9.046 9.112 
1/21/2010 8.778 8.817 8.963 8.862 8.854 9.053 9.085 9.14 
1/28/2010 8.815 8.885 8.963 8.884 8.713 9.049 9.124 9.136 
2/4/2010 8.818 8.877 8.963 8.9 8.741 9.098 9.167 9.154 
2/17/2010 8.815 8.887 8.996 8.924 8.868 9.116 9.202 9.171 
2/25/2010 8.894 8.992 8.963 9.058 9.009 9.129 9.297 9.298 
3/5/2010 8.908 8.911 8.978 8.961 8.89 9.087 9.179 9.197 
3/13/2010 8.813 8.832 8.963 8.903 8.841 9.063 9.075 9.152 
3/25/2010 8.821 8.84 8.963 8.879 8.863 9.045 9.097 9.156 
3/31/2010 8.828 8.884 9.033 8.912 8.877 9.114 9.215 9.213 
4/8/2010 8.787 8.782 8.963 8.841 8.823 9.004 9.055 9.089 
4/15/2010 8.747 8.841 8.963 8.86 8.843 8.976 9.002 9.017 
4/29/2010 8.771 8.843 9.026 8.841 8.811 8.945 8.923 8.924 
5/6/2010 8.746 8.824 8.963 8.867 8.778 8.924 8.833 8.847 
5/13/2010 8.831 8.931 9.015 8.938 8.911 8.967 8.948 9.000 
6/2/2010 8.753 8.746 8.963 8.842 8.771 8.817 8.589 8.891 
6/9/2010 8.751 8.84 8.963 8.814 8.784 8.803 8.565 8.867 
6/17/2010 8.774 8.859 8.991 8.838 8.802 8.837 8.57 8.891 
7/7/2010 8.749 8.832 8.963 8.831 8.781 8.805 8.548 8.891 
7/15/2010 8.81 8.768 8.963 8.879 8.836 8.691 8.525 8.851 
7/21/2010 8.755 8.779 8.963 8.781 8.827 8.687 8.464 8.851 
8/5/2010 8.733 8.771 8.963 8.774 8.802 8.744 8.407 8.834 
8/12/2010 9.077 9.018 9.242 9.104 9.061 9.644 8.378 8.691 
8/19/2010 8.882 8.94 9.044 8.959 8.957 9.369 9.241 9.09 
 
 85 
 
 
TRANSECT B       Bank= 9.613  
Piezometer B1 B2 B3 B3b B4 B5 B6 B7 B8 
Topography Elevations 9.488 9.679 9.594 9.594 9.640 9.356 9.636 9.687 9.500 
7/15/2009 8.965 8.747 8.716 9.018 8.696 8.529 8.461   
7/22/2009 9.002 8.761 8.717 9.018 8.708 8.438 8.408   
7/24/2009 9.037 8.777 8.756 9.021 8.742 8.617 8.394   
7/29/2009 9.028 8.758 8.742 9.024 8.724 8.649 8.427   
8/5/2009 9.018 8.771 8.746 9.018 8.721 8.698 8.501   
8/12/2009 9.014 8.754 8.731 9.018 8.718 8.67 8.394   
8/20/2009 9.022 8.753 8.735 9.018 8.722 8.663 8.358   
8/27/2009 9.019 8.757 8.833 9.018 8.821 8.676 8.465   
9/9/2009 9.062 8.787 8.771 9.018 8.755 8.792 8.562   
9/16/2009 9.05 8.794 8.773 9.018 8.752 8.781 8.539   
9/23/2009 9.04 8.77 8.751 9.018 8.75 8.735 8.503   
9/30/2009 9.059 8.795 8.781 9.018 8.76 8.777 8.602   
10/7/2009 9.062 8.782 8.762 9.018 8.765 8.734 8.517   
10/14/2009 9.062 8.801 8.771 9.018 8.774 8.724 8.478   
10/21/2009 9.067 8.808 8.802 9.028 8.783 8.828 8.868   
10/29/2009 9.124 8.913 8.897 9.053 8.895 8.891 9.162   
11/4/2009 9.075 8.82 8.802 9.028 8.791 8.89 8.947   
11/11/2009 9.097 8.822 8.829 9.028 8.792 8.886 8.95   
11/18/2009 9.091 8.821 8.822 9.018 8.786 8.882 8.916   
12/2/2009 9.072 8.825 8.805 9.018 8.797 8.909 8.956   
12/9/2009 9.638 9.47 9.493 9.539 9.392 9.745 9.251   
12/16/2009 9.115 8.862 8.848 9.043 8.846 9.036 9.018   
12/30/2009 9.156 8.865 8.851 9.046 8.868 8.989 9.016   
1/6/2010 9.084 8.828 8.853 9.039 8.811 8.94 8.993 9.093 9.193 
1/13/2010 9.066 8.806 8.796 9.039 8.799 8.922 8.94 9.056 9.361 
1/21/2010 9.018 8.832 8.82 9.018 8.81 8.857 8.975 9.039 9.342 
1/28/2010 8.883 8.924 8.58 9.27 9.461 8.78 8.982 9.217 9.401 
2/4/2010 9.094 8.848 8.826 9.038 8.828 8.92 8.987 9.231 9.418 
2/17/2010 9.126 8.875 8.829 9.049 8.892 8.946 8.998 9.246 9.462 
2/25/2010 9.177 8.961 8.986 9.041 8.957 9.01 9.284 9.324 9.582 
3/5/2010 9.149 8.88 8.859 9.018 8.846 8.961 9.034 9.304 9.446 
3/13/2010 9.102 8.865 8.832 9.079 8.862 9.007 9.041 9.153 9.397 
3/25/2010 9.122 8.86 8.826 9.041 8.863 8.933 9.048 9.161 9.397 
3/31/2010 9.128 8.872 8.814 9.029 8.843 8.931 9.018 9.188 9.449 
4/8/2010 9.107 8.823 8.795 9.018 8.777 8.892 9.031 9.113 9.318 
4/15/2010 9.074 8.816 8.786 9.018 8.77 8.858 8.858 9.107 9.329 
4/29/2010 9.066 8.809 8.808 9.018 8.794 8.838 8.814 9.064 9.347 
5/6/2010 9.046 8.796 8.781 9.018 8.755 8.798 8.732 8.933 9.084 
5/13/2010 9.118 8.898 8.884 9.018 8.841 8.777 8.802 8.824 9.142 
6/2/2010 9.018 8.796 8.762 9.018 8.751 8.776 8.54 8.708 8.824 
6/9/2010 9.014 8.791 8.781 9.018 8.741 8.737 8.531 8.623 8.804 
6/17/2010 9.019 8.803 8.787 9.018 8.744 8.744 8.539 8.582 8.794 
7/7/2010 9.007 8.782 8.772 9.018 8.737 8.733 8.525 8.574 8.778 
7/15/2010 9.053 8.818 8.819 9.018 8.79 8.679 8.55 8.605 8.81 
7/21/2010 9.003 8.785 8.76 9.018 8.73 8.677 8.462 8.597 8.709 
8/5/2010 8.968 8.765 8.672 9.018 8.739 8.699 8.398 8.581 8.693 
8/12/2010 9.134 9.107 9.125 9.383 8.888 9.592 9.084 8.963 8.575 
8/19/2010 9.012 8.964 8.9 9.13 8.929 9.238 9.121 8.888 9.258 
 
 
 
 
 86 
 
TRANSECT C      Bank= 9.283 
Piezometer C1 C2 C2c C3 C4 C5 C6 
Topography Elevations 9.009 9.62 9.62 9.593 8.929 9.8 9.651 
7/15/2009 8.752 8.72 8.901 8.634 8.596   
7/22/2009 8.769 8.716 8.901 8.682 8.604   
7/24/2009 8.796 8.751 8.92 8.715 8.637   
7/29/2009 8.787 8.745 8.901 8.702 8.615   
8/5/2009 8.769 8.741 8.902 8.701 8.617   
8/12/2009 8.778 8.731 8.927 8.699 8.615   
8/20/2009 8.794 8.731 8.926 8.691 8.604   
8/27/2009 8.784 8.726 8.916 8.694 8.619   
9/9/2009 8.844 8.76 8.926 8.729 8.644   
9/16/2009 8.836 8.759 8.924 8.694 8.695   
9/23/2009 8.828 8.754 8.921 8.713 8.767   
9/30/2009 8.845 8.763 8.921 8.732 8.814   
10/7/2009 8.842 8.761 8.901 8.718 8.798   
10/14/2009 8.865 8.771 8.921 8.736 8.817   
10/21/2009 8.858 8.774 8.921 8.743 8.877   
10/29/2009 8.914 8.861 8.941 8.836 8.963   
11/4/2009 8.863 8.783 8.901 8.754 8.866   
11/11/2009 8.869 8.784 8.901 8.762 8.883   
11/18/2009 8.868 8.782 8.901 8.76 8.873   
12/2/2009 8.862 8.789 8.901 8.758 8.883   
12/9/2009 9.324 9.359 9.464 9.355 9.585   
12/16/2009 8.893 8.825 8.927 8.799 8.918   
12/30/2009 8.898 8.825 8.94 8.702 8.856   
1/6/2010 8.892 8.794 8.924 8.766 8.832 8.877 8.911 
1/13/2010 8.845 8.772 8.913 8.792 8.825 8.852 8.958 
1/21/2010 8.855 8.774 8.901 8.747 8.856 8.873 8.988 
1/28/2010 8.908 8.796 8.901 8.771 8.937 8.888 9.051 
2/4/2010 8.896 8.823 8.901 8.77 8.927 8.891 9.059 
2/17/2010 8.878 8.837 8.901 8.789 8.906 8.887 9.063 
2/25/2010 8.956 8.907 9.031 8.92 9.043 9.05 9.107 
3/5/2010 8.934 8.835 8.901 8.81 8.955 8.915 9.033 
3/13/2010 8.884 8.809 8.901 8.796 8.909 8.903 8.965 
3/25/2010 8.896 8.821 8.901 8.824 8.985 8.881 8.955 
3/31/2010 8.885 8.836 8.901 8.802 8.93 8.923 8.888 
4/8/2010 8.848 8.801 8.901 8.757 8.862 8.885 8.861 
4/15/2010 8.868 8.793 8.901 8.755 8.828 8.851 8.834 
4/29/2010 8.836 8.79 8.901 8.756 8.871 8.796 8.812 
5/6/2010 8.832 8.772 8.901 8.768 8.813 8.735 8.664 
5/13/2010 8.886 8.848 8.901 8.871 9.109 8.899 8.878 
6/2/2010 8.82 8.752 8.901 8.712 8.853 8.678 8.47 
6/9/2010 8.823 8.754 8.901 8.713 8.863 8.665 8.403 
6/17/2010 8.844 8.76 8.901 8.718 8.874 8.667 8.412 
7/7/2010 8.835 8.754 8.901 8.715 8.864 8.656 8.402 
7/15/2010 8.886 8.715 8.901 8.773 8.89 8.718 8.446 
7/21/2010 8.965 8.749 8.901 8.704 8.907 8.569 8.371 
8/5/2010 8.931 8.743 8.901 8.63 8.897 8.575 8.316 
8/12/2010 9.044 8.909 8.946 8.831 9.434 8.932 8.504 
8/19/2010 8.942 8.822 9.431 8.799 9.076 8.683 9.072 
 
 
 87 
 
 
TRANSECT D       Bank=9.165 
Piezometer D1 D2 D2d D3 D4 D4d D5 D6 
Topography Elevations 9.138 8.986 9.001 9.479 9.613 9.452 9.551  
7/15/2009 8.555 8.511 8.568 8.501 8.352    
7/22/2009 8.553 8.502 8.568 8.504 8.758    
7/24/2009 8.583 8.535 8.568 8.535 8.782    
7/29/2009 8.572 8.52 8.634 8.519 8.769    
8/5/2009 8.573 8.523 8.613 8.505 8.773 8.735   
8/12/2009 8.573 8.513 8.63 8.505 8.755 8.727   
8/20/2009 8.564 8.507 8.588 8.516 8.77 8.702   
8/27/2009 8.565 8.494 8.603 8.508 8.777 8.732   
9/9/2009 8.6 8.538 8.602 8.53 8.787 8.761   
9/16/2009 8.595 8.537 8.608 8.529 8.79 8.774   
9/23/2009 8.595 8.521 8.588 8.527 8.772 8.772   
9/30/2009 8.617 8.546 8.628 8.554 8.787 8.752   
10/7/2009 8.604 8.523 8.626 8.525 8.784 8.797   
10/14/2009 8.6 8.536 8.578 8.547 8.789 8.772   
10/21/2009 8.611 8.546 8.588 8.553 8.807 8.842   
10/29/2009 8.665 8.629 8.613 8.605 8.899 9.034   
11/4/2009 8.614 8.554 8.605 8.558 8.808 8.846   
11/11/2009 8.616 8.553 8.602 8.565 8.806 8.859   
11/18/2009 8.615 8.547 8.588 8.563 8.804 8.855   
12/2/2009 8.633 8.547 8.603 8.554 8.807 8.85   
12/9/2009 9.175 9.169 9.151 9.167 9.437 9.447   
12/16/2009 8.652 8.602 8.631 8.606 8.84 8.924   
12/30/2009 8.64 8.597 8.602 8.6 8.874 8.907   
1/6/2010 8.623 8.571 8.61 8.566 8.835 8.856 8.696 9.029 
1/13/2010 8.597 8.538 8.602 8.563 8.83 8.803 8.794 9.113 
1/21/2010 8.6 8.476 8.568 8.546 8.746 8.853 8.764 9.063 
1/28/2010 8.647 8.579 8.586 8.569 8.857 8.863 8.871 9.034 
2/4/2010 8.633 8.579 8.588 8.58 8.866 8.87 8.883 9.054 
2/17/2010 8.63 8.623 8.599 8.595 8.877 8.877 8.905 9.085 
2/25/2010 8.731 8.677 8.66 8.689 8.944 9.078 9.05 9.211 
3/5/2010 8.679 8.63 8.599 8.608 8.874 8.901 8.914 9.064 
3/13/2010 8.673 8.585 8.568 8.615 8.896 8.852 8.863 9.014 
3/25/2010 8.655 8.562 8.568 8.569 8.857 8.856 8.874 9.025 
3/31/2010 8.663 8.494 8.568 8.629 8.858 8.901 8.91 9.088 
4/8/2010 8.608 8.552 8.568 8.561 8.818 8.816 8.833 8.971 
4/15/2010 8.657 8.555 8.568 8.563 8.842 8.807 8.784 8.947 
4/29/2010 8.626 8.538 8.568 8.547 8.821 8.787 8.613 8.879 
5/6/2010 8.586 8.528 8.568 8.526 8.792 8.748 8.684 8.776 
5/13/2010 8.658 8.609 8.568 8.614 8.89 8.893 8.588 8.722 
6/2/2010 8.591 8.509 8.568 8.509 8.772 8.832 8.474 8.521 
6/9/2010 8.576 8.516 8.568 8.522 8.783 8.782 8.393 8.488 
6/17/2010 8.57 8.508 8.568 8.514 8.775 8.776 8.386 8.485 
7/7/2010 8.566 8.508 8.568 8.505 8.768 8.761 8.378 8.479 
7/15/2010 8.621 8.456 8.568 8.517 8.749 8.769 8.433 8.526 
7/21/2010 8.566 8.501 8.568 8.486 8.67 8.764 8.389 8.48 
8/5/2010 8.581 8.256 8.568 8.331 8.617 8.76 8.379 8.473 
8/12/2010 8.731 8.256 8.568 8.287 9.002 8.844 8.403 8.669 
8/19/2010 8.737 8.448 8.67 8.706 8.971 9.443 8.564 9.013 
 
 
 
 
 88 
 
TRANSECT E       Bank= 8.535 
Piezometer E1 E2 E2e E3 E4 E5 E6 E7 
Topography Elevations 8.737 9.445 9.445 9.16 9.176 9.168 9.567 9.287 
7/15/2009 8.658 8.442 8.652 8.7 8.469 8.465   
7/22/2009 8.679 8.425 8.652 8.71 8.487 8.516   
7/24/2009 8.707 8.452 8.652 8.721 8.505 8.631   
7/29/2009 8.696 8.449 8.652 8.713 8.51 8.545   
8/5/2009 8.678 8.444 8.652 8.694 8.513 8.609   
8/12/2009 8.665 8.436 8.652 8.698 8.491 8.521   
8/20/2009 8.679 8.437 8.652 8.698 8.5 8.525   
8/27/2009 8.701 8.439 8.667 8.699 8.499 8.545   
9/9/2009 8.71 8.461 8.683 8.71 8.508 8.6   
9/16/2009 8.701 8.448 8.713 8.703 8.501 8.541   
9/23/2009 8.699 8.445 8.652 8.694 8.494 8.559   
9/30/2009 8.712 8.451 8.652 8.707 8.522 8.535   
10/7/2009 8.686 8.441 8.652 8.706 8.514 8.53   
10/14/2009 8.712 8.453 8.652 8.714 8.515 8.542   
10/21/2009 8.708 8.458 8.652 8.709 8.511 8.536   
10/29/2009 8.733 8.506 8.672 8.777 8.577 8.614   
11/4/2009 8.68 8.451 8.652 8.719 8.521 8.542   
11/11/2009 8.692 8.462 8.652 8.72 8.536 8.546   
11/18/2009 8.688 8.458 8.652 8.716 8.534 8.543   
12/2/2009 8.651 8.441 8.652 8.721 8.521 8.55   
12/9/2009 9.408 9.005 9.067 9.226 9.062 9.059   
12/16/2009 8.75 8.519 8.669 8.796 8.583 8.62   
12/30/2009 8.722 8.496 8.669 8.776 8.563 8.598   
1/6/2010 8.68 8.497 8.672 8.745 8.551 8.579 8.82 8.77 
1/13/2010 8.669 8.48 8.652 8.736 8.545 8.558 8.781 8.696 
1/21/2010 8.642 8.412 8.652 8.736 8.545 8.436 8.854 8.807 
1/28/2010 8.714 8.492 8.652 8.745 8.554 8.558 8.861 8.891 
2/4/2010 8.706 8.513 8.652 8.742 8.563 8.606 8.888 8.909 
2/17/2010 8.703 8.527 9.02 8.777 8.575 8.625 8.913 8.938 
2/25/2010 8.773 8.573 8.766 8.895 8.653 8.688 9.012 9.037 
3/5/2010 8.703 8.53 9.024 9.076 8.665 8.602 8.901 8.925 
3/13/2010 8.7 8.493 8.742 8.769 8.638 8.494 8.831 8.912 
3/25/2010 8.717 8.514 8.672 8.76 8.625 8.565 8.845 8.893 
3/31/2010 8.712 8.571 8.652 8.77 8.584 8.606 8.909 8.968 
4/8/2010 8.697 8.49 8.652 8.707 8.566 8.566 8.792 8.862 
4/15/2010 8.511 8.478 8.652 8.695 8.54 8.571 8.704 8.781 
4/29/2010 8.663 8.487 8.652 8.728 8.531 8.56 8.678 8.753 
5/6/2010 8.66 8.446 8.652 8.718 8.52 8.539 8.614 8.635 
5/13/2010 8.722 8.499 8.652 8.742 8.584 8.601 8.717 8.557 
6/2/2010 8.642 8.351 8.652 8.702 8.516 8.52 8.4 8.388 
6/9/2010 8.649 8.35 8.652 8.702 8.512 8.526 8.425 8.409 
6/17/2010 8.641 8.347 8.652 8.695 8.498 8.54 8.431 8.405 
7/7/2010 8.636 8.341 8.652 8.688 8.481 8.525 8.418 8.398 
7/15/2010 8.654 8.364 8.652 8.721 8.502 8.553 8.463 8.434 
7/21/2010 8.593 8.34 8.652 8.644 8.461 8.485 8.396 8.409 
8/5/2010 8.541 8.313 8.652 8.655 8.402 8.422 8.342 8.392 
8/12/2010 8.599 8.548 8.675 8.888 8.442 8.558 8.542 8.579 
8/19/2010 8.799 8.582 8.652 8.738 8.562 8.615 8.96 8.881 
 
 
 
 
 
 89 
 
TRANSECT F, G, H  Bank F= 8.427   Bank G= 8.412  Bank H= 8.411 
Piezometer F1 F2 F2f F3 F4 G1 G2 G3 H1 H2 
Topography Elevations 9.36 9.188 9.94 9.728 9.687 9.769 9.841 9.687 9.765 9.719 
7/15/2009 8.448 8.38 8.391        
7/22/2009 8.451 8.433 8.391        
7/24/2009 8.467 8.445 8.555        
7/29/2009 8.471 8.477 8.59        
8/5/2009 8.463 8.492 8.582        
8/12/2009 8.438 8.454 8.556        
8/20/2009 8.442 8.433 8.567        
8/27/2009 8.437 8.445 8.567        
9/9/2009 8.42 8.433 8.533        
9/16/2009 8.41 8.427 8.545        
9/23/2009 8.377 8.412 8.531        
9/30/2009 8.42 8.437 8.568        
10/7/2009 8.43 8.427 8.55        
10/14/2009 8.407 8.424 8.552        
10/21/2009 8.411 8.487 8.553        
10/29/2009 8.489 8.573 8.693        
11/4/2009 8.443 8.535 8.544        
11/11/2009 8.439 8.536 8.546        
11/18/2009 8.427 8.523 8.544        
12/2/2009 8.431 8.551 8.567        
12/9/2009 8.816 8.67 9.155        
12/16/2009 8.512 8.625 8.663        
12/30/2009 8.512 8.68 8.656        
1/6/2010 8.491 8.604 8.628 8.72 8.601 8.34 8.734 8.571 8.654 8.664 
1/13/2010 8.489 8.565 8.626 9.018 8.798 8.436 8.891 8.796 8.713 8.684 
1/21/2010 8.419 8.641 8.562 9.211 9.183 8.338 8.918 8.817 8.732 8.795 
1/28/2010 8.493 8.599 8.63 9.283 9.261 8.348 8.929 8.813 8.734 8.869 
2/4/2010 8.497 8.602 8.637 9.292 9.273 8.35 8.919 8.823 8.739 8.862 
2/17/2010 8.516 8.613 8.643 9.31 9.356 8.353 8.811 8.716 8.742 8.835 
2/25/2010 8.596 8.68 8.823 9.342 9.276 8.666 9.24 9.023 9.008 9.108 
3/5/2010 8.542 8.647 8.664 9.317 9.463 8.395 8.937 8.849 8.778 8.886 
3/13/2010 8.511 8.621 8.642 9.283 9.295 8.332 8.878 8.81 8.709 8.81 
3/25/2010 8.491 8.617 8.624 9.302 9.352 8.354 8.86 8.872 8.845 8.86 
3/31/2010 8.513 8.599 8.672 9.313 9.333 8.41 9.031 8.922 8.911 8.912 
4/8/2010 8.529 8.461 8.616 9.346 9.243 8.339 8.887 8.847 8.805 8.802 
4/15/2010 8.456 8.567 8.612 9.17 9.188 8.34 8.898 8.828 8.754 8.802 
4/29/2010 8.468 8.515 8.601 9.044 9.104 8.336 8.868 8.789 8.651 8.786 
5/6/2010 8.466 8.504 8.603 8.965 9.003 8.334 8.881 8.762 8.626 8.762 
5/13/2010 8.525 8.511 8.683 8.905 8.942 8.388 8.925 8.849 8.8 8.869 
6/2/2010 8.464 8.488 8.589 8.905 8.821 8.304 8.812 8.701 8.682 8.836 
6/9/2010 8.461 8.475 8.586 8.853 8.777 8.329 8.848 8.721 8.705 8.847 
6/17/2010 8.457 8.476 8.58 8.86 8.785 8.32 8.816 8.716 8.688 8.835 
7/7/2010 8.448 8.462 8.569 8.85 8.774 8.311 8.808 8.709 8.68 8.827 
7/15/2010 8.507 8.528 8.654 8.873 8.799 8.351 8.86 8.749 8.742 8.856 
7/21/2010 8.467 8.483 8.606 8.85 8.779 8.318 8.855 8.734 8.67 8.736 
8/5/2010 8.449 8.446 8.563 8.832 8.757 8.282 8.839 8.71 8.638 8.72 
8/12/2010 8.682 8.605 8.746 8.733 8.643 8.566 9.166 8.793 8.819 8.897 
8/19/2010 8.502 8.434 9.083 9.108 9.017 8.505 9.061 9.003 8.812 9.149 
 
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