SEDIMENTOLOGICAL RESPONSE OF THE 2007 REMOVAL OF A LOW-HEAD DAM, OTTAWA RIVER, TOLEDO, OHIO
Nathan Harris
A Thesis
Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
August 2008
Committee:
James E. Evans, Advisor
Enrique Gomezdelcampo
Sheila J. Roberts
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ABSTRACT
James E. Evans, Advisor
The Secor dam was a low-head dam that was 17m wide and 2.5 m tall on the Ottawa
River in Toledo, Ohio. The dam was removed for liability reasons and to facilitate
improvements in water quality and fisheries habitat on November 19, 2007. This study
documents the fluvial response of dam removal using: (1) repeated high resolution channel
surveying with a total station, (2) differential GPS measurements of bedform migration, (3)
bedload sampling using a Helley-Smith bedload trap, (4) multiple cores and (5) grain size
analyses of the channel substrate. The research also examined the applicability of the conceptual
channel evolution model of Doyle et al. (2003) and the predictive success of Dam Removal
Express Assessment model (DREAM-1) of Cui et al. (2006).
The results highlight the impact of reservoir sediment characteristics in fluvial responses
to dam removal. The Secor dam only trapped sand-sized bedload, thus rather than the initial
flush of suspended load sediment, the response was rapid incision and mobilization of the
material from the upstream delta of the former impoundment. The breaching of the dam resulted
in rapid upstream migration of a diffuse nick-zone approximately 10-m in length and
downstream migration of a sediment wave that translated at rates up to 0.5 m/hr. Within five
months, an estimated 514-m3 of sediment had been removed from the former delta and was redistributed into pools immediately upstream and downstream of the former dam.
Channel incision was the dominate process over the first two weeks of the study, with net incision as much as approximately 1-m in some locations. One month after removal, the channel iii
began to slowly widen and widening has been the dominate process during the subsequent 4 months.
The Secor dam removal differed fundamentally from other dam removals in the literature for the following reasons: (1) the impounded sediment was relatively homogenous, (2) a well defined channel already existed behind the impoundment, (3) the substrate was cohesionless and
(4) incision was dominated by nick-zone migration not nick-point migration. As a result, channel evolution occurred quickly, mobilizing sediment from the former delta almost immediately, as opposed to other studies which have reported erosion from the upstream delta taking years to decades. Thus, the channel evolution model proposed by Doyle et al. (2003) failed to predict the initial phases of removal of the Secor dam, which was dominated by uniform degradation of the channel bed behind the dam instead of evolving via nick-point migration.
The DREAM model adequately predicted the net volume of sediment removed from the former impoundment, only differing from the estimated value by -1.7 % The model, however, may not be used during the later phases of dam removal because the model failed to predict channel widening which may result in an underestimation of the volume of sediment removed from the former impoundment.
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For my wife and parents. v
ACKNOWLEDGMENTS
First and foremost, I wish to thank God for directing me to Bowling Green State
University in the first place; completion of this thesis is a living example that with God all things
are possible. Secondly, I wish to thank my wife, Kylie, for her constant patience and understanding as we completed this next phase of our life together. I would also like to thank my parents, David and Alena Harris, who first gave me the opportunity to attend college 6 years
ago and continue to inspire me in so many areas of my life. The completion of this project was
made possible through the dedicated efforts of my advisor, Dr. James E. Evans and committee
members Dr. Enrique Gomezdelcampo and Dr. Shelia J. Roberts. Thank you, also, to the
following research partners: The Village of Ottawa Hills, Toledo Metropolitan Area Council of
Governments, University of Toledo, Ohio Environmental Protection Agency, US Army Corps of
Engineers, and Ohio Department of Transportation, as well as to the Ohio Geological Survey for
use of the vibracorer. In addition, I would like to thank the Ohio Environmental Protection
Agency, the Geological Society of America, and Bowling Green State University for the funding
of this project.
I would also like to extend special gratitude to all those who graciously dedicated
countless hours to assist me with data collection. Without the selfless giving of these people, the
completion of this project would not have been possible: Dr. James Evans, Andrew Clark, Steve
Sabo, Jessica Lawrence, Steven King, Mary Scanlan, Allen Adams, Chris Pepple, Thor Zednik ,
Kylie Harris, Matt Bradford, Zach Mueller, and Colleen O’Shea. It is the time spent with the
people listed previously that truly made my graduate experience at Bowling Green State
University unforgettable. vi
TABLE OF CONTENTS
Page
INTRODUCTION ...... 1
Implications of dam emplacement and removal……………………………………. 2
Modeling dam removal……………………………………………………………… 10
Purpose……………………………………………………………………………… 10
BACKGROUND…………………………………………………………………………… 12
Bedrock Geology…………………………………………………………………... 12
Structural Geology…………………………………………………………………. 12
Glacial Geology……………………………………………………………………. 14
METHODS…………...... …… 17
Ottawa River……………………………………………………………………….. 17
Secor Dam…………………………………………………………………………. 22
Previous Work……………………………………………………………………… 25
Secor Dam Removal………………………………………………………………... 28
Field Survey Methods...... 30
Analysis of Survey Data……………………………………………………. 32
Error Analysis………………………………………………………………. 33
Sediment Cores……………………………………………………………………… 40
Bedload Traps ...... 41
Grain Size Analysis...... 41
DREAM-1 Model...... 47
Zero Process...... 57 vii
Description of model input...... 57
RESULTS…………… ...... 64
Lithofacies……...... 64
Fluvial Pavement Facies...... 64
Interpretation...... 64
Cross bedded facies...... 64
Interpretation...... 64
Rippled Sand Facies...... 66
Interpretation...... 66
Inundite Facies...... 66
Interpretation...... 66
Mud Drape Facies...... 67
Interpretation...... 67
Bioturbated Sand Facies...... 67
Interpretation...... 67
Massive Sand Facies...... 68
Interpretation...... 68
Overbank mud Facies...... 68
Interpretation...... 68
Reservoir Sediment Characteristics ...... 68
Former Ottawa River Channel Characteristics ...... 74
Downstream Channel Characteristics...... 77
Dam Removal Observations ...... 78 viii
Week 1...... 78
Week 2...... 82
Week 4...... 94
Week 6...... 95
Week 9...... 95
Week 13 ...... 98
Week 21...... 100
Bedload Measurements...... 101
DREAM Modeling Results...... 104
DISCUSSION ……………...... 108
Cross-Section Data...... 108
Sediment Transport...... 109
Comparison of the Secor dam to other dam removals...... 112
Comparison of the substrate of the former
and present channels of the Ottawa River...... 117
Comparison of DREAM-1 With Actual Data...... 118
CONCLUSIONS……...... 124
REFERENCES ...... 126
APPENDIX A TOTAL STATION SETUP ...... 132
APPENDIX B SEDIMENT PUSH CORES...... 135
APPENDIX C BEDLOAD GRAINSIZE STATISTICS...... 145
APPENDIX D CORE GRAIN SIZE STATISTICS...... 163 ix
LIST OF FIGURES
Figure Page
1 Number of dams removed in the twentieth century...... 3
2 Height and length of dismantled dams through time...... 4
3 Expected bedform, textural, and geomorphic adjustments of a fluvial system in
response to changing sediment supply in relation to transport capacity...... 6
4 Graph of T* vs S* to predict the response of dam construction...... 7
5 Stratigraphic section of the study area...... 13
6 growth and decay of glacial lakes in the Lake Erie Basin
between 16 and 5 Ka...... 15
7 Study area with cross-section locations ...... 18
8 Stage height vs discharge and exceedance probability
of the Ottawa River...... 20
9 Discharge and precipitation during the time of study
of the Ottawa River...... 21
10 Suspended sediment discharge of the Ottawa River...... 23
11 Secor Dam photographs with a scale...... 24
12 Secor Dam removal photographs in chronological order ...... 29
13 Difference DEM used to determine the volume of sediment
removed from behind the former Secor Dam ...... 34
14 Cross-section #3 that was surveyed twice prior to removal to assess error...... 35
15 Error analysis of survey methods for cross-section #6, #8, and #13 ...... 36
x
16 Map depicting the location of the former Ottawa River
channel and core locations...... 42
17 Bedload data collected upstream and downstream
after the removal of the Secor Dam ...... 44
18 Channel evolution through a former impoundment upon dam removal...... 50
19 Diagram of the variables for equations # 5 and #6 ...... 52
20 DREAM model response to sediment deposition and erosion
during a simulation at each cross section...... 55
21 Average bed material grain size distribution
input in the DREAM-1 model...... 59
22 Diagram of the geomorphic features in the Ottawa River ...... 70
23 Core photographs of the mud drape, inundite,
cross bedded and fluvial pavement facies...... 71
24 Vibracore of a point bar deposit taken from meander bend 1...... 72
25 Core Photographs of the lower and upper point bar of meander bend 2 ...... 73
26 Stratigraphy of the abandoned channel of the Ottawa River ...... 75
27 Typical core photograph of the abandoned Ottawa River ...... 76
28 Photograph of the nick-zone that developed immediately after removal ...... 79
29 Diagram of the sediment-wave propagation downstream ...... 80
30 Depiction of erosional narrowing ...... 83
31 Survey data of each cross-section surveyed multiple times...... 85
32 Photographs of slumps formed after removal...... 96
33 Difference DEM depicting the depth of erosion of sediment...... 99 xi
34 Bedload data collected upstream and downstream
Of the Secor dam after dam removal ...... 102
35 Diagrams depicting the change in Qs through time ...... 103
36 Diagram of bed elevation changes through
time predicted by the DREAM-1 Model ...... 106
37 Bedload histograms of grain size distribution
upstream and downstream of the former dam on 11/29/07 ...... 110
38 Channel evolution model through a former reservoir through time ...... 113
39 Surveyed geomorphic adjustments plotted against the
predicted geomorphic adjustments of the DREAM-1 Model...... 120 xii
LIST OF TABLES
Table Page
1 Contaminants with their associated sediment quality guidelines ...... 27
2 Chronology of field data collection after dam removal...... 31
3 Error analysis results of surveyed results...... 39
4 Bedload data collected upstream and downstream ...... 43
5 Formulas for calculating grain size statistics...... 46
6 Discrete intervals of fine-grained substrate
impounded by the Secor Dam...... 60
7 Description of Lithofacies...... 65
8 Comparison of the Predicted area removed from each
cross-section compared to the actual calculated area removed ...... 123
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INTRODUCTION
Dams have made a significant contribution to human development worldwide;
these structures have provided valuable resources such as hydroelectric power, water
supply, flood control, navigation, and recreational areas (Pohl, 2002). The construction of
dams in the United States increased from the mid-1800s until the 1960s (Lorang and
Aggett, 2005). There are approximately 75,000 large dams in the United States and, if
the definition of a dam were extended to include the smallest structures, the number may
exceed 2 million (Graf, 1999; FEMA, 2006). Large dams are defined as structures that
exceed 2 m in height and 61,700 m3 of storage or 8 m in height and 18,500 m3 of storage
and are recorded in the U.S. Army Corps of Engineers (USACE) National Inventory of
Dams (Graf, 1993; Smith et al., 2002).
Despite their many benefits, dams are one of the most significant anthropogenic
disturbances worldwide (Dynesius and Nilsson, 1994; Vorosmarty et al., 1997). The lifespan of most dams is approximately 60-120 years due to both gradual deterioration of
the structure and the reservoir infilling with sediment (American Society of Civil
Engineers, 1997). It is estimated that more than 85 % of the dams in the United States
will be near the end of their operational lives by 2020 (FEMA, 2006). Previously, repair
and upgrading have been the best options to deal with aging and substandard dams
(Doyle et al., 2003a). However, many small dams are privately owned and are too great
of a financial burden to continue to maintain, so removal is increasingly being considered
as a viable management option (Pohl, 2002). Data from thirty-one small dams that were removed revealed that the lowest estimate of repair costs was three to five times higher
than the cost of removal (Trout Unlimited, 2001; Graber, 2002). Despite interest in
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removing some larger dams, most of the dams removed in the past few decades have
been much smaller structures (Figures 1 and 2).
An estimated 500 dams have been removed in the U.S. during the last century and that number is only expected to increase in the upcoming decade (Graber, 2002). Often, small dams are privately owned or have been taken over by state and local governments when no owner is found. Larger structures, however, are commonly newer, federally- owned, better maintained, and still have economic value; thus are less likely to be removed.
Implications of Dam Emplacement and Removal
Dams have significant geomorphic and ecological impacts that are well documented in the literature (e.g. Magilligan and Nislow, 2005; Williams and Wolman;
1984; Gottschalk, 1964). A better understanding of the magnitude of these impacts has led to a recent re-evaluation of the usefulness of these structures. For example, it has long
been known that dam emplacement leads to sediment storage upstream and bed
degradation downstream (Gottschalk, 1964). Recently, however, studies have revealed a more complex relationship between dam emplacement and the resulting fluvial adjustments related to flow regulation, such as downstream aggradation (Williams and
Wolman, 1984). The idea that all dams are effective trappers of sediment (Brune, 1953)
has been recently revised by studies showing that small run-of-the- river dams trap very
little sediment (Brune, 1953; Meade et al., 1990). Thus, the downstream changes can be
complex, such as textural shifts in grain-size distribution (increased armoring or fining of
the bed), or channel pattern changes such as meandering to braiding transitions (Grant
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200
180
160
140
120
100
80
number of dams removed 60
40
20
0 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s
Figure 1: Diagram depicting how the number of dam removals has increased in the twentieth century. Note the dramatic increase in the number of dams removed since 1970 (modified from Pohl, 2002).
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50 Mean Maximum 40
30
20 Height (m)
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0 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s
4500 mean 4000 maximum 3500 3000 2500 2000
Height (m) 1500 1000 500 0 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s
Figure 2: (A) Diagram depicting the height of dismantled dams through time. (B) Diagram depicting the length of dismantled dams through time. Note the increase since 1970 in the maximum length and height of removed dams, but the mean height and length of dams indicates relatively small structures were removed (modified from Pohl, 2002).
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et al., 2003; Figure 3).
Predicted downstream effects of dams are largely related to two variables—flow
and sediment supply, where these variables may be quantified by the following ratios:
* S = SB/SA [EQ 1]
* T = Tpost/T pre [EQ 2]
Where SB is the sediment supply below the dam, SA is the sediment supply above the
* dam, S is the dimensionless supply ratio, Tpost is the frequency of sediment transporting
flows after dam construction, Tpre is the frequency of sediment transporting flows prior to
* dam construction and T is the dimensionless frequency of critical flows.
Using these equations, Grant et al. (2003) created a simplified bivariate plot of S*
and T* to identify the geomorphic end-member of a fluvial system (Figure 4). The plot
can be used as a first-order predictive tool in extreme cases where dam emplacement
causes T* to become much greater than S* or vise versa, but may not be used to describe
the rate at which these morphologic changes occur. For example, where sediment
transport events occur frequently, and downstream sediment supply is low relative to
upstream sediment supply, increased armoring of the bed is expected and erosion of the
channel bed, bar and island deposits could occur (Leopold et al., 1964; Williams and
Wolman, 1984; Galay et al., 1985). In contrast, Dietrich et al. (1989) reported that
frequent sediment transport events coupled with high rates of introduced sediment loads
into the downstream reach below a dam may give rise to poorly sorted or armored
6
Figure 3: Expected bedform, textural, and geomorphic adjustments of a fluvial system in response to changing sediment supply in relation to transport capacity (modified from Grant et al., 2003).
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Figure 4: Response domain for predicted channel adjustments in relation to the fractional change in frequency of sediment transporting flow (T*) and the ratio of the sediment supply below the dam to the supply above the dam (S*). End-member responses are shown note however that the dashed diagonal region is strongly dependent on local geological factors inherent to each dam site and are difficult to predict. See text for further explanation (modified from Grant et al., 2003).
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channel beds with abundant fines. When sediment transport events are infrequent and downstream sediment supply is high, channel response may include aggradation (Church,
1995; Collier et al., 1996), and/or braiding (Church and Kellerhals, 1978; Petts, 1984;
Grant et al., 2003). In these cases spatial variability is also significant, for example, bars
and islands may also form near tributary confluences (Grant et al., 2003). Regardless of
frequency of transport events, there may be little or no change in the downstream channel
(Grant et al., 2003).
The middle of the plot of Figure 4 has a region where downstream adjustments
following dam closure are unpredictable because adjustments are strongly dependent on
transient variables such as sediment supply, flow competence, and capacity (Grant et al.,
2003). Although the graph constructed by Grant et al. (2003) gives an idea of the
adjustments following dam emplacement, the variable fluvial response requires that the
geomorphic adjustments associated with dam emplacement must be examined on a case-
by-case basis to determine the proper means of removal.
It has been well documented in the literature that the emplacement of dams causes
multiple adverse effects on the ecological community (Baxter, 1977). Dams modify the
hydrology, nutrients, sediment dynamics, and water temperatures as well as the structure
and dynamics of aquatic and riparian habitats (Gray and Ward, 1982; Poff and Hart,
2002). However, simply removing a dam does not guarantee an immediate return to pre-
dam conditions. For example, dam removal may adversely affect the ecological
community downstream due to an increase of suspended sediment downstream or release
of contaminated sediment (Doyle et al., 2003b). The 1973 removal of the Fort Edward
dam on the Hudson River resulted in the blockage of downstream canals with sediment
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and the downstream transport of PCB-contaminated sediment (Shuman, 1995). Thus,
careful planning and assessments of the impounded sediment must be carried out prior to
dam removal.
Hypothetically, removing a dam should reverse its effects, altering fluvial
sediment budgets by erosion of stored sediment and its transport downstream (Doyle et
al., 2005). Cases studies of dam removals document an initial pulse of fine-grained
sediment followed by a long-term downstream migration of coarser-grained sediment
from the former delta (Cantelli et al., 2004; Evans, 2007). The net effect is governed by
the quantity of impounded sediment and the transport capacity of the fluvial system, with
upstream erosion of reservoir sediment driving the magnitude of the downstream
responses (Rathburn and Wohl, 2002).
The geomorphic adjustment to upstream and downstream reaches following dam
removal should be most discernable directly adjacent to the dam removal and then
decrease exponentially with both distance and time primarily due to a decrease in
sediment supply from the former impoundment and the establishment of quasi-
equilibrium conditions (Doyle et al., 2002). From the given available data, initial
removal causes the mobilization of the fine-grained sediment adjacent to the former dam
followed by a slower decay of the coarser-grained delta deposit upstream (Evans, 2007).
Although the majority of adjustments have been reported to occur one to five years after removal, downstream migration of bedload from the delta may take much longer and has
been poorly documented in the literature (Doyle et al., 2005; Evans, 2007).
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Modeling Dam Removals
The distance and rate at which the sediment travels downstream and the locations
of deposition are critical issues in the area of dam removal but these processes are
difficult to predict (Wohl and Cenderelli, 2000). Evans et al. (2002), for instance, used
sediment routing calculations to predict erosion of the impounded sediment and its
deposition downstream. Some studies have begun to use predictive one-dimensional
models to determine areas of deposition with some success (e.g. Rathburn and Wohl,
2001; 2003; Syed et al., 2004), but more studies need to test the validity of these models.
Predicting fluvial responses is also complicated because rivers are complex and the
response occurs over decades or centuries, making even simple fluvial processes difficult
to test or evaluate (Pizzuto, 2002).
Purpose of This Study
Additional studies are needed to determine the consequences of removal which
will become more important as a multitude of dams surpass their life expectancy in the
United States during the next decades. In this study, the 2007 removal of the Secor dam
provides an excellent opportunity to document changes in sediment transport, and the
resulting geomorphic response to dam removal. Thus, detailed observations of the
geomorphic adjustments following removal plus the quantitative data collected will be
evaluated in the context of expected morphological adjustments following removal. In
addition, these observations, coupled with the repeated survey measurements and other data, will be used test the channel evolution model proposed by Doyle et al. (2003b) and modified by Evans (2007) that describes fluvial adjustments following removal. The field data collected will also be used to assess the accuracy of a model called “DREAM-
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1” which predicts the fluvial adjustments associated with dam removals. Finally, the bed material obtained from multiple push cores in the Ottawa River will be compared to vibracore data analyzed from an abandoned channel of the Ottawa River to determine if there have been any changes in the substrate type of the river since dam emplacement in the early 1920s.
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BACKGROUND
Bedrock Geology
The bedrock in the Ottawa River watershed consists of several different Early to
Late Devonian sedimentary rock units that are predominately argillaceous dolostones and limestones (Figure 5). The Ottawa River downcuts stratigraphically down-section from the Antrim Shale near its head waters, into the Tenmile Creek Dolostone, the Silica
Formation, the Dundee Limestone, the Lucas Dolostone and finally the Tymochtee
Dolomite. The latter unit is the bedrock that underlies the study area. The Devonian shales are interpreted to have been deposited in shallow, muddy, anoxic marine settings as evidenced by the abundance of organic material, fine-grained siliciclastics, and tempestite deposits (Coogan, 1996). The carbonates are interpreted to have formed in warm peritidal settings with a low siliciclastic input (Coogan, 1996). Within the study area the local bedrock is buried by glacial deposits that range in thickness from 31 to 43- m (Forsyth, 1968).
Structural Geology
There are relatively few structural features in Northwest Ohio. The major structural feature in the area is the Findlay Arch which is a subdivision of Cincinnati
Arch which extends from the Nashville Dome in Tennessee (Dott, and Batten, 1971).
The Findlay Arch extends to the east of the Ottawa River Drainage basin, and does not appear to have influenced the evolution of the Ottawa River watershed.
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Figure 5: Stratigraphic section of the study area: Note, however, that there is no surface exposure of bedrock units in the study area (Modified from Gallagher, 1978).
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Glacial Geology
The Ottawa River watershed drains into the Lake Erie basin and was strongly influenced by the evolution of the Lake Erie basin during the Late Cenozoic. The Late
Cenozoic history of Lake Erie is complex because of multiple Late Cenozoic glaciations, drainage disruption and subsequent isostatic uplift between glacial events (Larson and
Schaetzl, 2001). The last glacial event produced multiple ancestral lake phases within the watershed.
Lake Erie went through a series of evolutionary stages in the past 18 Ka (Leverett and Taylor, 1915, Forsyth, 1973; Larson and Schaetzl, 2001). The earliest lake phase documented is Glacial Lake Leverett which formed around 16 Ka from the advance of the Wisconsin ice sheet. The next proglacial lake formed as a result of the retreat of the
Wisconsin ice sheet, Glacial Lake Maumee, and it has been differentiated into three phases (Maumee I, II, III) by Leverett and Taylor (1915; Figure 6). The different Glacial
Lake Maumee phases formed as a result of varying outlet location within the basin.
Further retreat of the Wisconsin ice sheet around 13.6 Ka resulted in the coalescence of the Huron and Eire Basins to form Glacial Lake Arkona (Figure 6). As the aerial extent of Lake Arkona expanded, however, a lower outlet was uncovered causing a lower lake elevation which was called Glacial Lake Whittlesey (Forsyth, 1973). Further retreat of the Wisconsin ice sheet resulted in the connection of the Huron and Erie Basins forming
Glacial Lake Warren. Subsequently, a lower outlet caused lower water levels creating
Glacial Lake Wayne (Figure 6). At approximately, 12 Ka lake levels dropped due to the
establishment of the modern outlet at the Niagara River which was approximately 46
meters lower than today (Forsyth, 1973; Figure 6). This produced the initial low-level
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Figure 6: (A-H) Figures depicting the growth and decay of glacial lakes in the Lake Erie Basin between 16 and 5 Ka (From Larson and Schaetzl, 2001).
16
stage of Lake Erie which only had water in the deepest portions of the basin. Retreat of the Wisconsin ice sheet in the region resulted in isostatic rebound in the region, causing the outlet to rise to its present elevation. This final lake level rise has been responsible for an increased lake level of approximately 3.5-m in the western end of Lake Eire. The increased lake level has thus produced backwater conditions (“estuaries”) in all of the streams that empty into Lake Erie at Maumee Bay.
Evidence of these ancestral lake levels within the Ottawa River watershed have been documented by Gallagher (1978) from an examination of the soils. This study revealed discrete belts of sand ridges resting on top of glacial lacustrine silt and clay deposits. These discrete belts of sand are interpreted to represent former shorelines of different ancestral Lake Erie stages.
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METHODS
Ottawa River
The Ottawa River drains a 446 km2 low-gradient basin in Northwestern Ohio and discharges into the Maumee Bay in the western basin of Lake Erie near Toledo, Ohio
(Roberts et al., 2007; Figure 7). The upper portions of the watershed are largely agricultural that grades into more suburban areas downstream. Below river kilometer 10, the river is highly urbanized and has a long history of contamination from various industrial sites. A single USGS stream gauging station (# 04177000) at river kilometer
17.3 exists on the Ottawa River on the Stadium Road Bridge on the Campus of the
University of Toledo. The gauging station consists of a continuous record from 1977 to
2007 which is sufficiently detailed to calculate the recurrence interval of various storm events. The ten, twenty five, fifty, and one hundred year floods were calculated to be, 91,
127, 170 and 219 m3/s respectively. In addition, the stage discharge curve for the Ottawa
River and the flood recurrence interval graphs are provided in figures 8a and 8b. Due to the location of USGS gauging station however, discharge from Hill ditch, which joins the
Ottawa River approximately 30 meters below the former location of the Secor dam also contributes to the discharge recorded at this station (Figure 7). It is likely however, that this discharge contributes little to the overall discharge recorded at this stream gauging station.
The flood response of the Ottawa River is shown in figure 9 during the period of study and is plotted with the precipitation data. Overall, the Ottawa River is characterized by relatively low base flow and high peak flows. Figure 9 shows that transitions from base flow to peak flow occur almost instantaneously after most
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Figure 7: General location of the study area with a blow up view depicting the surveyed cross sections (modified from Roberts et al., 2007)
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intense storm events. Thus, the Ottawa Rivers response to precipitation events is described as flashy. Baker et al., (2004) described a similar response of rivers in northwest Ohio and attributed it to land use changes through time such as changes in crop production, and constructed ditches and channelized tributaries that rapidly carry runoff to fluvial systems. In this case, the Ottawa River is also strongly affected by urban storm drainage.
Few hydrology studies have been done on the Ottawa River except for a study by
Gallagher (1978). Gallagher’s study included discharge and sediment load. The suspended sediment load was calculated through repeated sampling. Suspended sediment sampling was done in accordance with the USGS techniques as described by Guy and
Norman (1970). The sampling technique consisted of a standard design (USDH-59) sampler shaped so that the sediment water mixture would enter through a brass nozzle and was collected in a small bottle. The data from May 1975 to November 1977 and was collected in a depth integrated manner by letting the sampler hit the bottom and then raising back to the water surface. Laboratory analysis consisted of determining the weight, in milligrams of the sediment per liter of water. The amount of sediment per unit volume was then multiplied by the total amount of water passing through the sampling site at the time of collection to determine Qs. All discharge data was obtained from the
USGS stream gauging station on the Ottawa River at the stadium road bridge on the campus of the University of Toledo.
Gallagher (1978) used the suspended sediment data plus the discharge data from the USGS gauging station to construct a suspended sediment discharge curve (Figure 10).
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a 4 1990-2007 data 3.5 1975-1977 data 3 2.5 2 1.5
Dishcarge (m3/s) 1 0.5 0 0.01 0.1 1 10 100 Stage Height (m)
b
Figure 8a: Diagram depicting the relationship between stage height and discharge, Note that there is a gap in data collection during the 1980’s. (b): Diagram depicting the flood exceedance probability of the Ottawa River. Further information is given in the text.
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100 0 90 1 80 2 70 3
/s) 60 4 3 50 5 40 6 Q (m 30 7 20 8 Precipitation (cm) Precipitation 10 9 0 10 11/1 12/1 12/31 1/30 Date
Figure 9: Mean daily discharge and precipitation hyetograph of the Ottawa River from 11/1/07 to 2/27/08. Note that during the first 20 days of November there was very little precipitation (~1.3 cm) so only the water released from the sluice gates (i.e. constant discharge) of the Secor dam was recorded by the downstream U.S.G.S. gauging station.
22
Although bedload measurements were not made in the study due to the inadequacy of
most bedload samplers, Gallagher estimated the percentage of bedload discharge from the
methods of Anttila and Tobin (1976) which uses suspended sediment load, channel
substrate and the texture of the suspended sediment. Gallagher (1978) estimated bedload transport to be between 10 to 35 percent of the total sediment discharge for the Ottawa
River.
Secor Dam
Prior to 2005, four small dams obstructed the flow from the Ottawa River. The three other dams were removed in 2005-2006, and the Secor Dam was removed in
November, 2007. The Secor Dam was a small weir located at river km 18.3 and that was
owned by the Village of Ottawa Hills (Roberts et al., 2007). It consisted of a cement weir
about 2.5-m tall and 17-m wide, with a small pool capacity (Figure 11a-b). Two
bulkheads that extended 10-m upstream and downstream of the dam rose an additional
0.5-m above of the structure (Figure 11). One of these bulkheads has been entirely
removed. The Secor dam was originally constructed in 1928 to provide a recreational
area for the Village of Ottawa Hills. The original channel was diverted in 1928 during
the construction of the Secor dam and is now within the modern floodplain. Its location
was determined via two methods: (1) the use of the original engineering plans for the
construction of the Secor dam and (2) by finding surface depressions on the modern
floodplain that were assumed be the result of differential compaction of the fill in the
former channel. The Secor dam was the most downstream obstruction on the Ottawa
River. During its last several years, three small sluice gates approximately 0.2 m2 in
diameter have been opened, but this did little to prevent pooling behind the dam due to
23
100 y = 2042x0.5898 /s) 3 R2 = 0.8719
10 water discharge (m water 1 0.0001 0.001 0.01 0.1 1 10 sediment discharge (m3/day)
Figure 10: Sediment graph showing suspended sediment discharge of the Ottawa River collected from March, 1976- December 1977. See the text for an explanation of the data collection methods (modified from Gallagher, 1978).
24
a
b
b
Figure 11: (a) Picture of the former Secor dam with the dimensions of the dam given. (b): Picture of the former Secor Dam looking across the top of the structure (Photo from Gottgens, 2004)
25 debris accumulating upstream.
Recently, there has been interest by the local community and multiple government agencies to remove the dam and restore the area to more natural conditions. The primary purpose of removal was to alleviate potential legal and financial liability from the village.
Removal would also act to improve water quality and was in accord with the Maumee
River Remedial Action Plan (RAP) under the Clean Water Act, and to restore fisheries.
Other benefits of removal include: 1) enhance the recreation quality of the river, 2) restore fisheries and allow migration, 3) aid in restoring Lake Erie coastal sediment budgets by allowing bedload to move downstream 4) to help in mitigate previous sediment contamination downstream by allowing the unimpeded movement of bedload downstream.
Previous Work
A feasibility study for the removal of the Secor dam was conducted by a group of researchers from Bowling Green State University and The University of Toledo. The preliminary results were reported in Gottgens et al. (2004) and the final report in Roberts et al. (2007). Sediment contamination of the sediment immediately upstream of the
Secor dam was assessed quantitatively by comparing analytical results to the threshold effect level (TEL), which represents the concentration below which adverse effects are expected to occur only rarely, and the probable effect level (PEL), which represents the concentrations exceeding the value would cause adverse ecological effects. Table 1 shows that of the ten trace metals examined from multiple sites immediately behind the impoundment only As, Cd, occasionally Ni and rarely Pb exceeded the TEL values, while
26
As (one out of 15 surface samples) and Cd (1 out of 15 subsurface samples) exceeded
PEL values, although these samples barely surmounted the PEL threshold (Roberts et al.,
2007). In addition, 7% of surface samples exceed TEL for PCB’s and 100% of surface
samples and 100% of surface/subsurface samples exceeded for PEL for PAH
(hydrocarbon contaminates; Roberts et al., 2007).
The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) from
the US Army Corp of Engineers (2003) was used to assess the removal of the Secor Dam
on the local flood regime. The 10-, 25-, 50-, and 100-year recurrence intervals were
simulated for two scenarios (both the dam present and the dam removed) to determine
any differences in the area flooded. The study showed there were little changes in the
area flooded upstream while downstream the 10- and 100- year floods inundated
approximately 5000 m2 more area than with the dam in place. Lastly, to determine the
rate that the impounded sediment would be removed from the former dam site, sediment routing calculations were used. It was determined that the bulk of sediment that would be mobilized after dam removal would be sand bedload during bankfull discharges. This would move and accumulate in pools downstream of the dam between river kilometers
18.2-13. Finally, it was predicted that fluvial adjustments would take from one to several decades (Roberts et al., 2007).
An ecological study done by Arceo (2005) contrasted the structure and composition of the fish community in the reaches immediately upstream and downstream of the Secor Road Dam. The diversity was determined using a seine at one location upstream and downstream of the impoundment during 6 sampling dates. Fish species were determined in the field, counted and assessed for parasitism. It was determined that
27
Table 1. Contaminants with their associated sediment quality guidelines (from Roberts et al. (2007) % exceedance for % exceedance for standards TEL PEL
TEL PEL surface subsurface surface subsurface Al (mg/g) 26 60 0 0 0 0 As (µ/g) 5.9 17 33 67 7 0 Cd (µ/g) 0.596 3.53 93 93 0 7 Cu (µ/g) 35.7 197 0 0 0 0 Fe (µ/g) 190 250 0 0 0 0 Ni (µ/g) 18 36 13 13 0 0 Pb (µ/g) 35 91.3 0 7 0 0 Zn (µ/g) 123 315 0 0 0 0 PAH (µ/kg) 260 3400 100 100 100 100 PCB (µ/kg) 34.1 277 7 7 0 0
28
the dam acted to inhibit the migration upstream of several species (e.g. Yellow perch
(Perca flavescens); Northern Pike (Esox lucius) and sunfish (Lepomis machrochirus),
caused decreased species diversity in its upstream reaches, and caused a higher incidence
of black spot parasitism in its upstream reaches. The recommendation given by Roberts
et al. (2007) and Arceo (2005) to the community and government agencies was that the
dam should be removed. A cooperative effort by Bowling Green State University
(BGSU), The University of Toledo (UT), The US Army Corps of Engineers (USACE),
Toledo Metropolitan Area Council of Governments (TMACOG), Ohio Department of
Transportation (ODOT), Ohio Environmental Protection Agency (OEPA), and the
Village of Ottawa Hills resulted in the removal of the Secor Dam in the late fall of 2007.
Secor Dam Removal
The dam was removed in a simple process over a three-day interval. Very little sediment
was removed, and the Ottawa River was allowed to readjust with little human
disturbance. Along with the removal of the Secor Dam, the west side bulkhead was
removed, re-graded, and armored with rip rap that extended from the former dam site to
the confluence with Hill Ditch (Figure 7). The dam was entirely removed down to the
elevation of the bed at the time of removal. The former spillway was remediated with a
constructed gravel riffle that extended several meters downstream. The east side bulk
head was to be retained and reinforced to prevent future bank erosion that may affect
Secor Road (figure 12a-d).
The dam removal process subsequently began on November 16th, 2007 when
29
Figure 12 a-d: Photos depicting the dam removal process in chronological order from initial deconstruction to initial breaching of the dam (Photos from Jim Evans).
30
debris and upstream sediment was removed from blocking the sluice openings, and the
sluice gates were opened more fully to allow pool drainage. The bulk of the dam was
removed between November 19th-21st, 2007. Site remediation continued episodically during the next month, being completed by December 12, 2007. Delays in the remediation process were primarily due to precipitation which raised discharge of the river to stage heights that prevented equipment from entering the channel.
Field Survey Methods
The sediment texture and channel morphology must be characterized in both the
downstream and upstream reaches of the impoundment prior to dam removal. Seventeen
cross-sections (Figure 7), were established with eleven upstream and six downstream of
the dam. A Topcon GPT-3003W total station was used to survey each cross-section. In
fine prism mode the total station has a measurement accuracy of ± 3mm at a range 1.5m-
250 m. A detailed description of the use of the total station may be found in Appendix A.
Each cross-section stretched between two survey pins that were placed during the surveys
prior to removal and located using a differential Trimble GPS base station with a UTM
coordinate accuracy of 0.5 ± 0.11 m. Points were measured along each cross-section at
approximately 1-m intervals. Prior to removal of the dam all sites were surveyed at least
once. After the dam was removed, all cross-sections were resurveyed at least once. In
addition, nine cross-sections were re-surveyed at five different times to obtain a high
resolution picture of the resulting geomorphic adjustments following removal (Table 2).
The cross-sections repeatedly re-surveyed were selected because these cross sections
were observed to have undergone significant geomorphic adjustments.
31
Table 2. Chronology of field data collection after dam removal
Date Description of data collected bedload measurements and tracked sediment 19-Nov wave with GPS
bedload measurements and tracked sediment 20-Nov wave with GPS
bedload measurements and tracked sediment 21-Nov wave with GPS
22-Nov bedload measurements
24-Nov bedload measurements
26-Nov bedload measurements
27-Nov bedload measurements
29-Nov bedload measurements
3-Dec resurveyed 8 cross-sections
bedload measurements and push core of 6-Dec downstream bar at cross section # 12
resurveyed 10 cross-sections and bedload 20-Dec measurements
1-Jan resurveyed 9 cross-sections
determined thickness of sediment accumulation 23-Jan at Secor Bridge
23-Feb resurveyed all 17 cross-sections
19-Apr resurveyed 10 cross-sections
32
Analysis of survey data
The total station recorded x, y, and z coordinates, which allowed the data to be manipulated in Arcmap so that various Digital Elevation Models (DEMs) could be generated of the river channel. Because of data gaps between adjacent cross-sections, a method of surface interpolation had to be used to provide sufficient data to construct the
DEMs. Kriging was the interpolation method used in order to interpolate the bed elevation between each of the cross sections. Other surface interpolation methods were also used (inverse distance weighted and spline) but these methods produced a relatively undifferentiated DEMs.
Kriging is a geostatistical method for spatial interpolation that can assess the quality of prediction with estimated prediction errors (Chang, 2006). Kriging assumes that the spatial variation of an attribute is neither totally random nor deterministic.
Instead, the spatial variation consists of three parts: a spatially correlated component represent variation of the regionalized variable; a “drift” representing a trend; and a random error component (Chang, 2006). In this study, ordinary kriging was used with a fixed circular search radius of 14 meters, and an output pixel size of 0.25 meters. The data from cross-sections #5-#11 collected prior to removal and approximately three months after removal were imported into Arc-GIS. An analysis mask was created which defined the area in which all GIS operations were performed. An analysis mask was used because only the channel bottom and the immediate channel sides changed significantly during the period of study. The advantage of an analysis mask instead of simply eliminating values, is that the analysis mask still uses points outside of the defined area to perform calculations which acts to eliminate edge effects. Edge effects are produced
33
where no data exists outside of a discrete zone adjacent to the channel, so there is less
data available for prediction purposes. Both surfaces were then kriged, creating two
DEMs (one for pre-dam removal and one for post-dam removal). The raster calculator,
which is used to perform mathematical operations on raster layers, was then used to subtract one DEM from the other producing a third DEM which depicts the depth of incision at each 0.25 m by 0.25 m pixel (Figure 13). Finally, the DEM was reclassified to determine the number of pixels in each of the 10 defined categories. The number of pixels in each category was then multiplied by the area of a pixel and the depth of incision to obtain a volume. Because each category had a maximum and a minimum value, this calculation was performed twice. The resulting range of volumes represents
the amount of sediment mobilized upon the removal of the Secor Dam.
Error Analysis
Several methods were used to assess the error in the surveying techiniques used in
the study. Prior to removal, cross section # 3 (Figure 7) was surveyed twice at two different dates (10/12 and 11/13/07) to examine any differences in the data. The results show that the two survey dates were nearly identical (Figure 14). The surveyed
difference in the channel cross-sectional area was 0.68 m2. This error may be smaller,
however, because some changes in cross-sectional area might be expected to occur
naturally. A second method used to assess survey error was by examining how the
surveyed position of the fixed pin, which varied between 0.26 to 0.82-m, varied from the
position determined by differential GPS (Figure 15 a-f). Table three reports the error
associated with each cross-section. As mentioned previously, the differential GPS unit
used has a horizontal UTM coordinate accuracy of 0.5 ± 0.11 m. Thus, with the
34
Figure 13: DEM created to show the difference in elevation of the channel bed between the pre-removal channel and Feb 23, 2008 (approx. 3 months following dam removal).
35
178.5 10/12/2007 178 11/13/2007 177.5 177 176.5 176 elevation (m) 175.5 175 174.5 0 5 10 15 20 width (m)
Figure 14: Diagram depicting site # 3 which was surveyed twice prior to removal. Note how the cross sections almost exactly overlay with the exception of areas where survey points were more coarsely spaced. The cross section (and all others) is oriented facing the downstream direction.
36
a
4615258.0 surveyed data GPS point 4615257.5
4615257.0
Northing (m) Northing 4615256.5
4615256.0 281616 281617 281618 281619 Easting (m)
b
4615236.5 surveyed data GPS point 4615236.0 ) m
ng ( 4615235.5 hi t o r N 4615235.0
4615234.5 281601 281602 281603 281604 Easting (m)
Figure 15: Plots showing the potential error of channel surveys using the total station. Each plot shows the surveyed UTM position of one of the cross-section pins. The cross shows the differential GPS location and error for the cross-section pin. It is likely that Figure D & F are anomalous due vegetation or by not placing the stadia rod directly adjacent to pin. (a) Error analysis of survey pin at cross-section # 6 NE side. (b) Error analysis of survey pin at cross-section # 6 SW side.
37
c
281619 surveyed data GPS pt 281618.5
281618
Northing (m) Northing 281617.5
281617 4615221 4615222 4615223 4615224 Easting (m)
d
4615240.0 surveyed data GPS point
) 4615239.5 m
ng ( 4615239.0 hi t o r
N 4615238.5
4615238.0 281631 281632 281633 281634 Easting (m)
Figure 15 (con’t.): (c) error analysis of survey pin at cross-section #8 NE side. (d) error analysis of survey pin at cross-section #8 SW side.
38
e
4615156.0 surveyed data GPS point 4615155.5
4615155.0
Northing (m) Northing 4615154.5
4615154.0 281614 281615 281616 281617 Easting (m)
f
4615158.5 surveyed data GPS data
) 4615158 m
ng ( 4615157.5 hi t o r
N 4615157
4615156.5 281640 281641 281642 281643 Easting (m)
Figure 15 (con’t.): (e) error analysis of survey pin at cross-section #13 E side. (f) error analysis of survey pin at cross-section #13 W side.
39
Table 3. Minimum, Maximum, and Average errors of Cross Section Data site # Average (m) Min (m) Max (m) 6, NW 0.26 0.06 0.42 6, SW 0.38 0.32 0.51 8, NW 0.63 0.44 0.88 8, SW 0.31 0.23 0.68 10, E 0.82 0.24 0.42 10, W 0.29 0.55 1.00
40
exception of Figure 15d-f, the surveyed data was accurate to the level of the differential
GPS uncertainty. It is likely that the additional error in Figure 15d-f may be attributed to
vegetation obscuring the total station line of sight (either it was not possible to put the
prism directly on the survey pin, or there was backscattering of the laser from the
branches) from one survey pin to the other.
Sediment Cores
Sediment cores or surface samples were collected at eleven cross-sections.
Sediment samples were taken at the following cross-sections, #1, #2, #3, #4, #5, #6, #10,
#11, #12, #15 and #16 (Figure 7; Appendix B). Samples were collected at three locations along each cross-section, one in the center of the channel, one on the left side of the
channel, and one on the right side of the channel. Two types of push core tubes were
used: a 5.08 cm diameter PVC pipe or a 7.8 cm aluminum irrigation pipe. Each core was
pushed to the maximum depth at which they could be retrieved. In instances where the channel was heavily armored, surface samples were collected by removing everything in a 20 cm by 20 cm square to a depth of 5 cm. In the laboratory, the cores were split lengthwise, photographed, described, and one half of the core was archived. The remaining half was sampled extensively for grain size analysis utilizing approximately
100-200 grams of sediment.
In addition to the push core data, six vibracores were collected in the former channel of the Ottawa River along with a single vibracore at point bar #2 upstream of the
Secor Dam. Vibracores were obtained using a vibracorer that pushed them into the substrate to the maximum depth until refusal. The position of the former channel was
41
surveyed using a differential GPS unit. The data was subsequently downloaded into
ArcGIS map and then plotted on an aerial photo along with the locations of the obtained
vibracores (Figure 16). The six vibracores were used to interpret the pre-1920s channel
substrate, using the method of Murphy et al. (2007).
Bedload Traps
Bed load traps were used to document changes in sediment transport following dam removal. A Helley-Smith bedload sampler with a 125µ mesh net was employed repeatedly downstream at the center of cross-section #15 prior the removal of the Secor dam (Table 4). This cross-section was selected because it is immediately adjacent to the dam and it was shallow and thus accessible under different flow stage heights. No bedload was recovered, however, from 11 bedload measurements under flow conditions ranging from 0.2 – 1 m3/s. Pre-dam removal bedload traps could not be used upstream
due to continuous high water behind the Secor dam. After dam removal, bedload
samples were collected at cross-sections number #4 and #15. For most samples the
sampler was deployed for fifteen minutes. Stream discharge data was obtained from the
USGS gauging station during each time of bedload sampling (Table 4; Figure 17 a-b).
The collected bedload samples were collected in the field and were thoroughly washed in
the laboratory, oven dried at 90°C for 12 hours and then sieved for grain size analysis
(Appendix C).
Grain Size Analysis
Grain size analysis followed ASTM protocols D-421 and D-422 (ASTM, 1986).
Samples were oven dried at 90 °C for 12 hours, and were disaggregated using a rubber tip
42
Figure 16: Map of abandoned Ottawa River with the core locations indicated. The abandoned Ottawa River is denoted with the dashed line.
43
Table 4. Bedload Samples Collected at Site #4 3 3 date flux (g/hr) Q (m /s) Qs m /s 11/20/07 1610 0.17 1.69E-07 11/20/07 1499.7 0.16 1.57E-07 11/21/07 6305.4 0.28 6.61E-07 11/22/07 1375.2 4.64 1.44E-07 11/24/07 3200 3.51 3.35E-07 11/26/07 499.6 5.15 5.24E-08 11/27/07 633.2 8.95 6.64E-08 11/29/07 2386 3.51 2.50E-07 12/9/07 0 1.47 0 12/20/07 104.4 3.17 1.09E-08 1/17/08 101.2 3.77 1.06E-08
Bedload Samples Collected at Site #14 3 3 date flux (g/hr) Q (m /s) Qs m /s 11/19/07 86 0.17 9.01E-09 11/22/07 472 4.50 4.95E-08 11/24/07 114.4 3.57 1.20E-08 11/26/07 116.8 5.15 1.22E-08 11/29/07 241.2 3.48 2.53E-08 12/20/07 0 3.14 0 1/17/08 138 3.77 1.45E-08
44
a
10 y = -5E-06x + 4.0377 8 R2 = 0.1473 /s) 3 6 Q (m 4
2
0 0 1E-07 2E-07 3E-07 4E-07 5E-07 6E-07 7E-07 3 Qs (m /s)
b
6 5 /s) 4 y = 4E-07x + 2.7501 3 Q (m 3 R2 = 0.1398 2 1 0 0.00E+00 1.00E-08 2.00E-08 3.00E-08 4.00E-08 5.00E-08 6.00E-08
Qs (m3/s)
Figure 17 (a): Bedload data collected upstream after removal. (b) Bedload data collected downstream after dam removal.
45
mortar-and-pestle. Sediment sizes greater than +4Φ were sieved in whole Φ increments
using a Rotap sieve shaker.
The Spectrex laser particle analyzer was used on the fine-grained sediment
fraction when more than ten percent of the total sediment sample passed through the +4
Ф sieve. Due to the presence of a large fraction of particulate organic material in most
samples, prior to the use of the laser particle size analyzer samples were treated with 5 ml
of 30% hydrogen peroxide solution until there was no longer a vigorous reaction. The samples were then heated on a hot plate for approximately one hour to allow for a more vigorous reaction and were subsequently allowed to cool for twenty-four hours to ensure complete digestion of organic materials. Large organic material that was not dissolved was removed with a forceps prior to analysis. After organics were removed, a small amount of sample was diluted with distilled water into a beaker so that the sample was diluted to 1 gm per 1000 ml. Five milliliters of Calgon solution was also added to the sample to ensure that clay particles would not flocculate prior to dilution. The sample was then extensively stirred for several minutes and was immediately placed in the particle size analyzer with a magnetic stirrer so that measurements could be obtained.
Grain size statistics including the mode, mean median and standard deviation and skewness were calculated for the grain size data using the methodology of Folk and
Ward (1957; Table 5). For each sample, cumulative weight percent vs. phi size class were graphed to obtain the percentiles used in the equations of Table 5 (Appendix D).
Histograms were also constructed to visually examine the skewness of the data
(Appendix D).
46
Table 5. Formulas for Calculating Grain-Size Statistics Graphic mean:
Mz = (Φ16+Φ50+Φ84)/3 Inclusive Graphic Standard deviation
σi = {(Φ84-Φ16)/4 + {Φ95-Φ5)/6.6} Inclusive graphic skewness:
Ski = {(Φ84+Φ16-2Φ50)/(2(Φ84-Φ16))} + {(Φ95 + Φ5 - 2Φ50)/(2(Φ84-Φ84))} formulas from Folk and Ward (1957)
47
DREAM-1 Model
The Dam Removal Express Assessment Model (DREAM) is the first hydraulic
model specifically designed for dam removal (Cui et al., 2006). Previously, studies
attempting to model dam removals primarily utilized HEC-6. However, HEC-6 is not
capable of simulating a steep slope (nick point) immediately upstream of a dam following
removal (Cui et al., 2006). To surmount this problem, previous researchers have
independently modeled the upstream reaches separately and used these results to define
the upstream boundary condition for the simulation of the downstream reaches.
However, this practice is only valid when part of the dam is still remaining effectively
separating the upstream and downstream reaches (Cui et al., 2006). Thus, these
combined models cannot be used for the simulation of a “single-shot” removal, and possibly may not be valid for the simulation of the later stages in a staged removal. This practice also ignores the sediment transported out of the system during the initial stages of removal which may underestimate the geomorphic and biologic implications of removal. Previous models that may be modified to model removal are those that can model sub-critical, supercritical, and transient flow conditions such as: SRH1-D (U.S
Department of Interior Bureau of Reclamation, 2006) or FLUVIAL-12 (Chang, 1998).
The DREAM model consists of two modules: DREAM-1 and DREAM-2.
DREAM-1 simulates the removal of a dam in which the reservoir is primarily composed of non-cohesive sand and silt, while DREAM-2 simulates sediment transport in which the upper layer of the deposit is primarily composed of gravel (Cui et al., 2006). Variables for channel characteristics may include any combination of bedrock, gravel bedded, and sand bedded fluvial systems for a DREAM-1 simulation and a combination of bedrock
48
and gravel-bedded rivers for a DREAM-2 simulation (Cui et al., 2006). The primary
inputs for the models include channel cross-sections, mean daily discharge, reservoir
sediment characteristics, thickness of the reservoir sediment, and annual upstream
sediment discharge.
Removal of small dams has become increasingly common in the US in the past
decades, although very few dams have been studied in detail (Figure 1). DREAM was
developed to predict the hypothesized morphological adjustments of a dam removal of
Doyle et al. (2003b). The model assumes that the dam removal process begins with the
construction of cofferdam to divert flow away from the dam so that dewatering of the
reservoir can occur. The sediment between the dam and the cofferdam is subsequently
excavated to expose the dam. The model allows for either a one-shot complete removal of the dam or a partial removal of the dam or the opening of a notch in the dam. After the dam has been completely or partially removed, the cofferdam is breached at a designed discharge. In the case of opening a notch in the dam, the model assumes that no flow control structures were emplaced. Upon breaching of the coffer dam, the model assumes that a steep slope develops in the substrate that may be equal to the particle angle of repose (Figure 18). This steep slope (or nick point) allows for rapid erosion within the reservoir. As the nick point migrates upstream, sediment is deposited downstream as a delta (Figure 18). The rapid down-cutting is assumed to divert flow from any secondary channels leaving them abandoned and perched (as observed by Evans, 2007). It is also assumed that the newly incised channel will have a similar hydraulic geometry to the reach found immediately downstream of the dam. Depending on the width of the reservoir and the active channel, parts of the former reservoir deposit may be left in place
49
in the form of terraces. Once the channel reaches a more stable gradient, however, the
channel may begin to migrate laterally and erode these terraces. The above description of the geomorphic adjustments is incorporated into DREAM, with the exception of lateral migration once the channel reaches a stable gradient.
For the purpose of flow calculations, the channel is assumed to be rectangular with width equal to the local bank-full width. Flow parameters are calculated with a combination of a standard backwater equation and a quasi-normal flow assumption:
2 dh/dx = S0 – Sf / 1-F when F< 0.9 (Eqn. 3)
S0 = Sf when F > 0.9 (Eqn. 4)
where h denotes water depth, x denotes the downstream distance; S0 denotes the channel
bed slope; Sf denotes the friction slope and F denotes the Froude number;
S0 = б(ηb+ηg+ηs) / бx (Eqn. 5)
2 2 2 3 F= Q w / gB h (Eqn. 6)
where ηb denotes the elevation of nonerodible material such as bedrock; ηg denotes the
thickness of the gravel deposit; ηs denotes the thickness of the sand deposit on top of the
nonerodible material; Qw denotes water discharge, g denotes the acceleration due to
gravity; B denotes the bank-full width; and h denotes depth. Figure 19 depicts some of
the terminology used above some of the terms used for the model.
Cui and Parker (1997) show the quasi-normal flow assumption provides a good
approximation of the full backwater equations when the Froude number is high. Cui and
Parker (2005) have used this flow assumption to simulate the evolution of sediment
pulses in gravel bed rivers; in this publication the flow is calculated with the backwater
equation whenever local Froude number is less than 0.75, and with a quasi-normal flow
50
Figure 18: Channel evolution through a former impoundment upon breaching of the coffer dam. Note that the channel erodes through the reservoir deposit via nickpoint migration with angles approaching the angle of repose. These geomorphic adjustments are incorporated into DREAM-1 and -2 (From Cui et al., 2006).
51
assumption otherwise. This allows the modeling of subcritical flow upstream of the
sediment pulse, the supercritical flow at the steep downstream face of the sediment pulse,
and the transient flows linking the two states.
This treatment recognizes the fact that sediment transport simulations are almost
always performed at a much coarser resolution (2-10 channel widths) than the scale of
transient flow so that it is not essential to model the exact location of transient features,
such as hydraulic jumps, as long as the model can predict the two points between which
the hydraulic jump will occur. Although the treatment is simplified, extensive
comparisons through multiple studies (e.g., Paola et al., 1992; Seal et al., 1997; Cui et al.,
1996; Cui and Parker, 1997) indicates that this method produces nearly identical results
as other more sophisticated methods and thus was incorporated into DREAM.
In order to calculate the sediment transport capacity in DREAM-1 it is assumed
that the bedload is primarily sand. The sediment transport equation that is employed by
the DREAM-1 model is the Brownlie (1982) bedload transport equation. This equation
was empirically derived from a very large database of flume experiments coupled with
field measurements and is as follows:
-3 1.978 .0.6601 -0.3301 Qs = [9.022x10 Qw(Fg-Fgo) Sf / R+1 (h/Dg) ] (EQN 9)
Where Qs denotes the volumetric sand transport rate, Fg denotes the particle Froude
number, Sf is the friction slope, Dg is the geometric grain size for sand and the other variables are defined in the following equations:
. 5293 -0.1405 -0.1606 Fgo = 4.596 τ *0 Sf σg (EQN 10)
-17.73Y τ*0 = 0.22Y + 0.06℮ (EQN 11)
0.5 -0.6 Y = [(RRg) ] (EQN 12)
52
Figure 19: Diagram depicting the various variables of equation five and six. Note that both sand and gravel sediment transport can only be modeled with DREAM-2 (modified Cui et al., 2006).
53
3 0.5 Rg = (gDg ) / ν (EQN 13)
Where, σg is the bed material (sand) geometric standard deviation, Sf is the total friction
slope, Rg is the particle Reynolds number, Dg is geometric mean grain size, ν is the
kinematic viscosity of water, g is the acceleration due to gravity and R is the submerged specific gravity of sediment particles (R= ρg)
In the use of the Brownlie (1982) bedload transport equation, Brownlie’s friction formulation must also be used. Brownlie (1982) assigned friction formulas to both lower flow regime (ripples and dunes) and the upper flow regime (upper plane bed and antidunes). The transition between lower and upper flow regimes depends on whether the
stage is rising or falling. The DREAM model, however, uses the mean daily discharge as
the flow input; the specifics about the rising and falling stage are not included in the
model. Instead, the average upper limit of the lower flow regime and the average lower limit of the upper flow regime are used to define the transition between the two flow regimes in the DREAM model. The DREAM model also replaces the median grain size with the mean grain size, arguing that the mean grain size better represents the grain-size distribution.
In the DREAM model Brownlie’s sediment transport equation is not used directly to calculate the sand transport rate. Instead, it is used to calculate the maximum amount of sand that may be transported over the bed. The actual sand that is transported therefore may or may not be the same as the sediment discharge calculated by Equation 9 based on the mass conservation equation given below (Equation7).
(1-λp) B(∂ηs / ∂t) + (∂Qs/ ∂ηx) = qsl (EQN 14)
where λp denotes the porosity of the deposit; t denotes time; Qs denotes the volumetric
54
transport rate of sand (calculated from Brownlie’s sediment transport equation) supply
rate per unit distance and qsl denotes the lateral sand supply rate per unit distance.
Bank erosion during the period of down cutting through of the former impoundment is
obtained from the Exner Equation of sediment continuity. The sediment is assumed to
have been deposited in a valley and the active channel is assumed to have a trapezoidal
cross-section with bank slopes at the angle of repose (Figure 20a-c). The Exner equation
assumes that in cases of channel aggradation or degradation, the active channel only
changes elevations along the bed while the bank slopes remain constant. The net result should be an increase in bottom width (Bb) during aggradation or a decrease in bottom
width during incision. In cases of channel incision, however, once the channel reaches a
predefined minimum (Bm), incision ceases and the channel begins erode both channel banks while preserving the trapezoidal shape of the channel (Figure 20a-c). The value of
Bm is selected by assuming similarities between the active channels above and below the
former impoundment. The bottom width of the channel downstream of the dam serves as
the minimum value for the bottom width of the trapezoidal channel upstream of the dam:
Bm = [B – (2Hb/tan θ)] (EQN 15)
where B denotes the average bankfull width adjacent to, and downstream, of the dam; Hb
denotes the average bankfull depth adjacent to the dam, and θ denotes the angle of the banks of the trapezoidal channel which is assumed to be approximately 35°.
The Brownlie’s bedload transport equation calculates the transport capacity of the bed material, which is primarily composed of sand-sized particles and may be transported either as bedload or suspended load. For simplicity, the model assumes that remobilized particles finer than sand are wash load, and will not to be deposited on the channel bed.
55
Figure 20: DREAM model response to sediment deposition and erosion during a simulation at each cross section. Note that when Bb = Bm bed lowering stops and the channel experiences erosion of its side banks (modified from Cui et al., 2006).
56
(Although wash load is defined as material that always remains in suspension, Cui et al.
(2006) use the term to refer to anything that has a grain size of silt or smaller that is being
transported or remobilized upon dam removal. The term wash load will only be referred
to here and in subsequent sections will be termed suspended load when referring to
material in transport or fine-grained substrate when discussing fine-grained material that
may be mobilized upon dam removal).
This portion of sediment, however, is included in the calculation of the total
suspended sediment. The following equation is used to determine whether material is
moving as suspended load:
Pm = Vs/kU* < 1
where Vs is the settling velocity of the particle calculated with the procedure of Dietrich
(1982), k is the von Karman constant with a value of 0.407, U* denotes the shear velocity
and Pm = the Rouse Number for a given grain size class m. When Pm ≥ 2.5 = bedload, Pm
≤ 0.8 = suspended load, 0.8 < Pm < 2.5 mixed load.
DREAM-1 and DREAM-2 utilize the mean daily discharge, and multiple stations
from associated tributaries may be input into the model. The long-term average sediment
supply is also required. Sediment supply is assumed to come from the upstream end of
the studied reach, therefore sediment supply from downstream of the dam is not
specifically built into the model, although significant erosion along a certain reach may
be treated as a tributary input to account for this sediment supply. The downstream
boundary condition includes the bed elevation and the water depth for the furthest
downstream cross-section, which remain fixed throughout the experiment.
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Zero process
A zeroing process is a way to ensure that the initial conditions that are input into
the simulation are valid and ensures that before running the model that the system is in a
quasi-equilibrium condition. Here quasi-equilibrium means that the river may experience
aggradation and degradation over different time periods, but overall long-term bed
elevation changes are limited within an expected or observed range for the modeled river
system. In the zeroing process, the model is run repeatedly under an appropriately
chosen reference condition. If the model shows excessive bed elevation changes then the input parameters may be varied to obtain more satisfactory results. The zero process allows for the validation of certain parameters such as the sediment supply rates, the elevation of the non-erodible layer and the thickness of the deposit. The zeroing process also is applied to the reaches downstream of the dam and the reference condition is based on the longitudinal profile just prior to removal. The input sediment supply is then introduced into the system as if there is no dam and the longitudinal profile and other parameters are modestly adjusted until the reach shows an acceptable amount of bed- level changes.
Description of model input
In this study, the downstream and reservoir channel widths were determined from field data by using a differential Trimble GPS base station with a UTM coordinate accuracy of 0.5 ± 0.11 m or from aerial photographs where parts of the river that could not be easily accessed. The model requires measuring bankfull width downstream of the dam. In this study, the valley walls are nearly vertical so it was hard to identify the
58
bankfull width. However, it is unlikely that caused error because the valley walls are
nearly vertical (width does not change significantly).
Although nineteen cross-sections were surveyed prior to dam removal, only
twelve cross-sections were input into the model. The excluded cross-sections were less
than two channel widths apart from one of the twelve cross-sections used. The cross-
sections input into the model were #1, #2, #3, #5, #8, #10, #11 #12, #14, #15, #16, #17
(Figure 7). According to Cui et al. (2006) using these additional cross-sections slow the
model’s run time without improving the accuracy of the experiment. In fact, the model only requires that five cross sections be defined upstream while 25 cross-sections are to be defined downstream.
The grain-size distribution was determined from the thirty-two push cores that were obtained prior to removal. At cross-sections where push cores were not obtained, the grain size distribution was assumed to be the same as the two adjacent cross-sections.
The input for DREAM-1 requires the grain size of the bed material along with any fine- grained substrate within the reservoir deposit. The model only allows for the input of one grain size distribution to characterize both upstream and downstream bed material
deposits. In this study the bed material was characterized from push cores. Figure 21
depicts the representative grain size distribution in the study. Any fine-grained substrate that is found within the reservoir is entered separately in another file. Depth increments are put in at each cross-section along with the percentage of fine-grained substrate found at that location (Table 6).
The model also requires the thickness of the reservoir sediments and downstream channel sediments and the depth-to-bedrock. These parameters define the slope in
59
100
80
60
40
20
0 Cumulative Weight Percent Cumulative -1 0 1 2 3 4 5 6 Phi Size Class
Figure 21: Average bed material grain size distribution of the study area that was input into the DREAM-1 model. Note that the DREAM-1 model describes all bedload within a reservoir from one grain size distribution.
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Table 6. Core data showing vertical changes in fine- grained (> +4Φ) substrate content cross-section #1 depth (m) 0 0.08 0.12 0.35 percent >+4 Φ 2.08 15.19 21.98 11.94 cross-section #2 depth (m) 0.25 percent >+4 Φ 8.14 cross-section #5 depth (m) 0 0.17 0.43 0.61 percent >+4 Φ 1.73 5.85 2.56 2.14 cross-section #10 depth (m) 0.05 0.27 0.42 percent >+4 Φ 4.91 8.99 8.38 cross-section #11 depth (m) 0.06 0.27 0.41 0.78 percent >+4 Φ 2.57 3.89 6.29 12.13
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DREAM-1. The depth to bedrock within the study area ranges from approximately 31–
43-m below the surface (Forsyth, 1968). Cui et al. (2006) have reported that excessively thick deposits of erodible material may cause the model to fail, however, and an arbitrary value may be used for depth-to-bed-rock provided that it is deep enough to not be eroded to. The bedrock elevation downstream of the dam was assigned a value of 10-cm below the surface. This value was chosen because during the period of simulation no erosion to this depth was reported by the model. The arbitrary depth to bedrock within the reservoir was assigned the original elevation of the channel constructed during the construction of the Secor dam. This arbitrary depth was chosen because the dam was to be removed to the elevation of the channel bed, thus the portion of the dam left in place will act as a grade control. Additionally, the glacial-lacustrine sediment below the reservoir deposit is much more cohesive and it is unlikely to be eroded significantly during the short simulation. Thus, it is unlikely that the channel will degrade below this arbitrary datum assigned during the initial months following the simulated removal.
The thickness of the deposit that had accumulated behind the Secor dam could not be estimated directly despite many attempts the using push cores. The 1928 engineering plans used to construct the Secor Dam showed that the new channel was excavated into glacial-lacustrine material; unfortunately no cores contained any glacial-lacustrine sediment. The presence of glacial-lacustrine sediment underlying the former reservoir deposit was later verified after some was recovered from multiple push cores upon removal of the Secor dam. Thus, an estimate of the thickness in this manner could not be done. To solve this, the original engineering plans for the construction of the Secor dam were used. In 1928, a new channel was created prior to the construction of the Secor
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Dam. The new channel constructed was approximately 198-m in length and had a slope of 0.06°. Using this channel information, the original bed elevation was subtracted from the current bed elevation to obtain the thickness of the deposit. The thicknesses of cross- sections #5, #8, and #10 were input into the DREAM-1 model as 0.62-m, 0.42-m, and
0.53-m respectively. Based on these calculations, and on an examination of the impoundment prior to removal during low flow conditions, the maximum extent of upstream sediment accumulation was only 100-m. This was confirmed after dam removal by the field observations of the upstream delta deposit.
The most difficult input parameter to determine was the rate of sediment supply.
The model requires a long-term average of the sediment supplied to the stream per year.
Unfortunately, the only data sources available were from a study by Gallagher (1978) based on two years of collection of suspended sediment data, and from the dam removal feasibility study by Gottgens et al. (2004) which reported an estimated volume of bedload impounded by the Secor dam between 4,500 and 9,000 m3. It is likely that the Secor dam trapped virtually all bedload transported to the dam site, but trapped little suspended load.
Thus, it may be assumed that an estimate of the yearly bedload supply can be determined from the given data. Because the Secor dam was constructed in 1928, it was calculated that the average rate of sedimentation over 79 years (1928-2007) was between 55-109 m3/yr.
The suspended sediment discharge curve constructed by Gallagher (1978) (Figure
10) consists of 91 samples that were collected over two years over a wide range of flow conditions (0.33 to 63 m3/s). Gallagher’s data, reported the suspended sediment discharge in tons per day, which needed to be converted to cubic meters per day to be
63 input into the model. Therefore, all suspended sediment was assumed to consist of quartz with a density of 2.65 g/cm3. After all the sediment data was converted into m3/day, ten years of the Ottawa River flood record were selected so that the annual suspended- sediment discharge could be calculated. Using the mean monthly records from 1985 to
1995 the annual suspended-sediment discharge was approximately 5.1 m3/year.
The last variable input into the DREAM model was the mean daily discharge for the duration of the experiment. This was obtained from a USGS stream gauging station approximately 1 km downstream from the Secor dam. The mean daily discharge from
November 19 to February 27 was used (Figure 9) to allow comparison with the actual data after removal.
64
RESULTS
Lithofacies
Fluvial Pavement Facies
The fluvial pavement facies consists massive, sub-angular to rounded, poorly
sorted, coarse sand to pebble, quartz with a minute amount of various anthropogenic materials (disaggregated tile drainage pipe, blocks, brick, cement, metal fragments, etc.; table 7). The facies ranges in thickness from 3-10 centimeters and is only present in the modern channel of the Ottawa River. The color of the facies was 2.5 Y 5/3 (light olive brown).
Interpretation: The fluvial pavement facies formed from the concentration of coarse- grained material due to the preferential erosion of finer-grained particles that are more easily mobilized. Most of the present channel bottom is covered by these fluvial pavement facies.
Cross-bedded sand facies
The cross bedded facies consists of cross bedded, rounded, moderately sorted,
fine- to medium-grained, quartz sand (Table 7). The individual cross-beds are shallowly
dipping and individual facies range from approximately 4 – 10-cm. This facies is present
in both the former channel and the present channel of the Ottawa River. The color of the
facies is 2.5 Y 5/3 (light olive brown).
Interpretation: The presence of cross-bedding within sand intervals represents the
migration of 2-D or 3-D dunes across the channel bottom. Dunes can be observed in the
present channel attached to the lower point bar.
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Table 7. Description of Lithofacies lithofacies description interpretation massive, rounded, moderately sorted, fine-grained to medium-grained, bioturbated quartz sand with vertical and bioturbated channel sand facies horizontal burrows deposits cross- cross bedded, rounded, moderately migration of 2-D or 3-D bedded sorted, fine-grained to medium- dunes across the channel sand facies grained, quartz sand bottom massive, poorly sorted, silt to fine flood couplets formed from sand, with organic material alternating deposition of bedload with massive to cross bedded, followed by quiescence and rounded, moderately sorted fine- settling out of organic and inundite grained to medium-grained, quartz fine-grained material from facies sand suspension massive, sub-angular to rounded, poorly sorted, medium sand to concentration of coarse- granule, quartz with a minute amount grained material due to the fluvial of various anthropogenic materials preferential erosion of finer- pavement (disaggregated tile drainage pipe, grained particles that are facies cement, metal, etc) more easily mobilized.
migration of asymmetric ripples across the channel asymmetric rippled, rounded, surface or over larger bed rippled sand moderately sorted, fine-grained to forms such as bars or facies medium grained, quartz sand) dunes settling out of silt in pools during waning flooding mud drape massive, silt to fine sand, with organic events or during periods of facies material low discharge. rapid deposition of bedload massive massive, rounded, moderately sorted, during the waning stages of sand facies fine- to medium-grained quartz sand. a flood
massive, moderately sorted very fine overbank deposition of fine- overbank sand to silt with pedogenic grained sediment during mud facies modification and root hairs. flooding events.
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Rippled sand facies
The rippled sand facies is described as asymmetrically rippled, rounded,
moderately sorted, fine- to medium-grained, quartz sand (Table 7). The facies was
described in both the former and present channels of the Ottawa River. The color of the
facies was 10 YR 6/2 (light brownish gray). The set height of individual ripples is
approximately 1-5-cm.
Interpretation: The rippled sand facies represents the migration of asymmetric ripples
across the channel surface or over larger bedforms such as bars or dunes. Such ripples can be observed today in the upper point bar, the tops of attached bars or on the channel banks after high stage height events.
inundite facies
The inundite facies was described as heterolithic, poorly sorted, silt to fine-
grained sand with organic material, alternating with massive to cross bedded, rounded,
moderately sorted fine-grained to medium-grained, quartz sand (table 7). The color of
the facies was described as 2.5 Y 2/0 (black) for the organic rich silt layer and 2.5 Y 4/2
(dark grayish brown) for the sandy unit. The facies is also gleyed in some push cores.
The facies is present in both the present and former Ottawa River channel.
Interpretation: It is hypothesized that the heterolithic, organic-rich- silt and sand
deposits are formed as a result of flooding. Such deposits are commonly called inundates.
Flooding events act to mobilize both fine- to medium-grained sand and mix them with particulate organic material, which may be brought into the Ottawa River from direct deposition from riparian vegetation, overbank flooding, or via storm drains in suburban and urban areas upstream. These organics are then mixed with a small amount of sand
67
and silt-sized particles. During flood events sand is transported to form the cross bedded
sand facies and/or the massive sand facies. After the flood wanes, however, the organic material and minute amount of suspended sediment is allowed to settle out of suspension resulting in organic-rich silt layers. These layers are subsequently covered up during the next flooding event. Thus, this facies consists of alternating deposits that are interpreted as couplets (rhythmites) representing bedload and suspended load from floods.
Mud Drape Facies
The mud drape facies is described as massive, rounded, moderately sorted, silt and clay (Table 7). The mud drape facies is primarily observed downstream of the former Secor Dam although it was also observed in some push cores behind the former dam. The color of the facies was described as 2.5 Y 2/0 (black).
Interpretation: Mud drapes are likely formed from the settling out of silt to very-fine- grained sand in pools during waning flooding events or during periods of low discharge.
Bioturbated sand facies
The bioturbated sand facies is described as massive, rounded, moderately sorted, fine- to medium-grained, quartz sand with bioturbation (Table 7). The deposits show disturbance features such as irregular bedding, mottling, and homogenization. This facies
is described in both the present channel and former channel of the Ottawa River. The
color was described as 7.5 YR 4/2 (brown).
Interpretation: This facies is interpreted as bioturbated channel deposits. The
bioturbation was sufficiently intense to destroy any primary sedimentary structures that
have formed previously.
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Massive sand facies
The facies is described as massive, rounded, moderately sorted, fine- to medium- grained quartz sand. The color is described as 7.5 YR 4/2 (brown). The facies is primarily found in the present Ottawa River channel.
Interpretation: This facies is interpreted to be massive as a result of rapid deposition of bedload during the waning stages of a flood. No indication of fluid escape structures were noted in the facies such as fluid escape pipes or dish structures, so it is unlikely that this resulted in the formation of the facies.
Overbank mud facies
The facies was described as massive, moderately sorted very fine sand to silt with pedogenic modification and root hairs. The color is described as 2.5 Y 2/0 (black). The facies was described in the vibracore from the point bar at meander bend 1.
Interpretation: The facies is interpreted to form as a result of the overbank deposition of fine-grained sediment during flooding events.
Reservoir Sediment Characteristics
The grain size distribution and nature of the sediment impounded by the Secor dam was determined through a series of thirty-two push cores and one vibracore
(Appendix C). Overall, the Secor dam acted as a bedload trap for sand and a small fraction of gravel. Trace amounts of silt-sized particles were also trapped behind the impoundment, intermixed with varying amount of organic matter. Much of the bedload was deposited in a delta between cross-sections # 5 and # 9, and directly behind the dam to a thickness of approximately 0.30-m.
Multiple push cores and a single vibracore were used to characterize the sediment
69
of the delta deposit (Figure 22). Internally, the delta deposit primarily consisted
heterolithic intervals (inundite facies) alternating with cross-bedded sandy facies that was
capped with the sandy rippled facies (Figure 23a). The organic-rich silts of the inundite
facies predominately consisted of leaves, small twigs, and other detrital organic material
in a silty matrix (Figure 23a). Earlier studies determined that the organic matter content
of the channel sediments range from 1.1 to 8% (Roberts et al., 2007). The delta deposit
graded downstream into a pool that consisted different sandy deposits that was capped by
a fluvial pavement.
Most push cores consisted of four lithofacies. The basal units of the push cores
were commonly inundite facies that were interbedded with cross-bedded sand facies,
bioturbated facies and massive sand facies. Individual couplets ranged in thickness from
1 to 5-cm. The sandier intervals of the inundite facies were commonly massive indicating rapid deposition. Capping these deposits was the fluvial pavement facies that ranged from 3 to 10-cm thick (Figure 23b).
A single, 2.45-m long vibracore obtained on the point bar at meander bend 1
(Figure 22) approximately 100-m upstream, provided some additional information about
the sediment characteristics (figure 24). The vibracore was divided into three facies
associations: the lower point bar, upper point bar, and overbank interval. The lower-point bar (1.88-2.45-m) consisted of the cross bedded sand facies 0.65-m thick capped by a fluvial pavement facies about 3-cm thick (Figure 24-25a). The lower-point bar abruptly transitioned to the upper point bar (0.50-1.88-m) that consisted of the inundite facies approximately 1.4-m thick (Figure 24-25b). Superimposed on the inundite facies is the bioturbated facies that acted to homogenize portions of the interval (Figure 25b).
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Figure 22: Diagram depicting several geomorphic features in the Ottawa River.
71
Inundite facies a b Fluvial Pavement facies
Cross-bedd ed sand facies
Massive sand facies
mud drape facies
Bioturbated sand facies
Figure 23 (a): Core photograph showing inundite facies, bioturbated sand facies cross- bedded sand facies and mud drape facies. Note how the bioturbated sand facies is superimposed on the inundite facies. (b): Core photograph of the fluvial pavement facies that was present at most locations upstream of the former Secor Dam along with the massive sand facies.
72
Figure 24: Vibracore of a point bar deposit taken from meander bend 1. See text for explanation.
73 a b Figure (
b bioturbated sand facies
Cross-bedded
sand facies
Inundite facies
mud drape
facies
Figure 25 (a): Picture depicting the lower point bar consisting of cross bedded sand facies. Figure (b): Picture depicting the upper point bar which consists of couplets of fine sand that alternates with organic-rich silt (inundite facies). Note that the bioturbated facies is superimposed on the inundite facies. The arrows of the bioturbated facies are pointing to homogenization produced from bioturbation and also a vertical burrow (b). See text for further explanation.
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The overbank mud facies interval (0-59 cm) capped the vibracore and was sporadically bioturbated (bioturbated facies).
The above facies associations comprise an idealized fining upward vertical succession of a point bar. The lower point bar association represents a channel deposit as indicated by the cross-bedded facies which likely formed as a result of dune migration across the channel bottom. As a result of meandering, the upper point bar association became superimposed on the lower point bar association. The upper point bar association is dominated by the inundite facies that is sporadically superimposed by the bioturbated facies. The inundite facies represents flood couplets that form as a result flooding which transports sand followed by the waning of the flooding events which allow the particulate organic matter and silt to settle out of suspension. Lastly, the overbank fines facies represents the overbank deposition of silt and clay as a result of flooding.
Former Ottawa River Channel Characteristics
As mentioned previously, the Ottawa River was diverted when the Secor Dam was constructed in 1928. Today, the former channel is buried underneath floodplain sediments. Five vibracores were taken in this former channel and revealed several aspects of the channel prior to impoundment. As indicated from Figure 26 there is approximately 0.8 to 1.4-m of sediment that was used to infill the former channel. All cores showed a similar stratigraphy and will be described together. The base of the sequence consisted of the inundite facies that abruptly transitioned into the bioturbated facies, cross-bedded sand facies, or rippled sand facies (Table 7: Figure 26-27).
Significantly, the former channel had no fluvial pavement facies; previous studies have
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Figure 26: Stratigraphy of the abandoned channel of the Ottawa River. The upper muddy portions of each column are a combination of artificial fill and recent overbank deposits with superimposed soils.
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Roots
Bioturbated facies
b
inundite facies
Figure 27: Typical core photograph of an abandoned Ottawa River core depicting the bioturbated facies that is underlain by the inundite facies. Note the burrow labeled b. Note the presence of roots near the top of the core photograph.
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linked fluvial pavements to urbanization (Grable and Harden, 2006). Figure 26 shows
some correlations of the cores that were obtained from the former channel and reveal that
the channel substrate was predominately medium-grained to fine-grained sand.
Downstream Sediment Characteristics
Sediment downstream of the Secor Dam was evaluated via push cores and channel substrate observations prior to removal of the Secor Dam. Immediately downstream (<30 m) of the dam the channel banks are armored with rip-rap, and the channel has a pool-and-riffle sequence that is armored with pebble to cobble-sized gravel and cement blocks emplaced during the 1928 construction of the dam. This riffle sequence grades downstream into a large pool approximately 30 m downstream and to a small fine-grained sand bar at the confluence of Hill Ditch (Figure 22). Another pool- and-riffle sequence composed of pebble-to-granule gravel formed downstream of the junction with Hill Ditch below the Secor Road bridge (Figure 22). Downstream of the bridge the channel banks are unarmored and are extremely steep, with some of the banks being nearly vertical. The channel substrate in this area consists primarily of rippled sand facies, although some of the deeper pools were observed with mud drape facies. Further downstream (0.1 to 1.4 km) four mid-stream channel bars were identified that were
described with rippled sand facies overlying cross-bedded sand facies.
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Dam removal observations
Week 1
The dam was breached during the morning of November 19, 2007. Initially, a
diffuse erosional step called a “nick-zone” migrated upstream. The nick-zone had a relief
of approximately 8-10-cm and migrated upstream approximately 83-m during the first
hours following removal (Figure 28). The prominent step in the nick-zone then stabilized
in one location, approximately 70-m upstream of the dam, because erosional downcutting
excavated a fairly widespread, horizon of cohesive inundite facies.
As a consequence of nick-zone migration upstream into sandy deposits, a sand-
wave developed approximately 10-m downstream of the stalled nick-zone. The sand-
wave translated downstream toward the former dam as a bedload sheet. The sand-wave
initially consisted of three lobes as the sand wave entered meander bend 2 (Figure 22;
Figure 29a-b). The sand-wave was continually tracked using a GPS unit during the next
two days. The rate of downstream translation changed from 0.5 m/hr during the first 12
hours and eventually slowed to a rate of 0.2 m/hr during the subsequent 36 hours.
Twelve hours after initial formation, however, only lobe 1 was actively migrating
downstream (Figure 29a-b) and bedform translation stalled as the sediment wave entered a pool. Lobe 1 continued to translate downstream on the inside of the first meander bend for the remainder of the first two days (Figure 22). On the third day (Nov. 21), a morning rainfall event caused a rapid rise in stage height which cased the lobe 1 to cease migration on the inside of the meander loop and reactivated lobes 2 and 3. This resulted in
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~ 15 cm of incision Outcrop of inundite facies
Nick zone
Figure 28: Picture depicting the position of the nick zone approximately 24 hours after removal. Note how the prominent step in the nick zone has stalled on a layer of organic- rich silt and sand (inundite). The relief on the nick zone is approximately 10 cm in this location while upstream the bed has degraded approximately 15 cm.
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a
Figure 29: Diagram depicting the sediment wave initiated during the first hours following the removal of the Secor Dam. (a) Diagram depicting the migration of the sediment wave during the first three days following the removal of the Secor dam. Note that the downstream migration of the sediment wave was tracked using a differential GPS unit.
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b
~1-m
Figure 29 (con’t.): (b) Photograph of the sediment wave on the morning of November 20th. Note the Stakes approximately 1-m tall for scale.
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deposition at the point bar apex in meander bend 1 (Figure 29a-b).
During the first days after dam removal, significant incision was observed within the area of the nick-zone and above this area up to a total distance of 84-m upstream of the former dam (Figure 28). The most significant incision was observed at cross section
#6 where a push core revealed that the channel had nearly eroded into the underlying glacial-lacustrine substrate which had not been seen in any of the pre-dam removal push cores obtained near this site (the maximum length of these cores was approximately 0.4- m). Other areas of significant incision included cross section #5, where approximately
0.15-m of incision was measured adjacent to the delta deposit (Figure 28). Even within the first few days after removal the main channel was observed to be narrower than the pre-dam removal channel (Figure 30).
There were few observed downstream geomorphic changes downstream of the dam during the first week after dam removal. During the first day, construction activity during the dam removal process acted to mobilize a minute amount of substrate as suspended load downstream. This moved as a diffuse sediment plume that quickly dissipated approximately 100-m below the former dam. Overall, very little sediment upstream of the former dam was mobilized or moved downstream any significant distance. One exception is that immediately downstream, a small amount of sand was observed between pebble-sized gravel at the first riffle.
Week two
From November 21 to December 3, a series of precipitation events and high-stage
A 83
B
Figure 30: (a) Picture depicting the reservoir just prior to removal. Note that white box depicts the approximate area in the second photo. (b) Depicts erosional narrowing that occurred immediately after the breaching of the Secor Dam. Note that these images may be compared because the stage height was constant as recorded from the gauging station downstream. The position of the stakes depicts the location of the sediment wave.
84
flow induced additional geomorphic adjustments. These became apparent when the
cross-sections were resurveyed on December 3rd. The flooding event acted to create a
large point bar around the meander bend between cross-sections # 7 and #10 that were
similar to the point bar described at meander bend 2. The newly constructed point bar
consisted of the cross-bedded sand facies (lower-point bar) that graded upward to the rippled sand facies on the upper-point bar. Deposition occurred at the apex of the point bar.
Observations of the former impoundment indicate that the substrate changed significantly from week one. Immediately adjacent to the former dam, a prominent layer of organic-rich silt and fine sand (inundite facies) had been excavated and formed a step within the river channel. Further upstream of the impoundment the channel was armored with the exception of a few sporadic, organic-rich silt rip-up clasts that were up to 0.4-m in diameter. A small portion of the upstream delta behind the former Secor Dam was eroded due to channel widening.
During the second week after dam removal, eight cross-sections were resurveyed upstream and downstream of the impoundment. All upstream cross-sections revealed significant incision but very little widening. Channel incision ranged from approximately
0.2-m (cross-section #3) to a max of approximately 0.7-m in a large scour that formed at cross-section #6 (Figure 31A-P). Adjacent to the former delta, cross-section #5 degraded approximately 0.6-m and also widened slightly (Figure 31E). The channel slightly widened in the region from the preferential undercutting of the inundite facies which rested above more easily erodible fine-to medium-grained sand. The organic-rich layers
85
179 A 178.5 178 177.5 177 prior to removal 176.5 2/23/2008 176
Elevation (m) 175.5 175 174.5 174 0102030 Distance (m)
B 179 178.5 178
) 177.5 m
( 177
n prior to removal o
i 176.5 2/23/2008 176 evat l
E 175.5 175 174.5 174 0102030 Distance (m)
Figure 31: Channel cross-sections collected prior to and after the removal of the Secor dam. All cross sections are oriented so that you are looking downstream. The left side of each chart represents the east to north east side of the channel while the right side of each cross-section is the west to southwest bank of the Ottawa River. See figure 7 for the exact location of each cross section. (A) cross-section #1 (B) cross-section #2.
86
179 C 178.5 178 prior to removal 177.5 12/3/2007 177 12/20/2007 176.5 1/1/2008 176 2/23/2008 Elevation (m) 175.5 4/19/2008 175 174.5 174 0 5 10 15 20 25 Distance (m)
D 179 178.5 178
) 177.5 m
( 177 prior to removal n o
i 176.5 2/23/2008 176 4/19/2008 evat l
E 175.5 175 174.5 174 0 5 10 15 20 25 Distance (m)
Figure 31 (con’t.): (C) cross-section #3 (D) cross-section #4.
87
179 E 178.5 178 prior to removal 177.5 12/3/2007 177 12/20/2007 176.5 1/1/2008 176 2/23/2008 Elevation (m) 175.5 4/19/2008 175 174.5 174 0 102030 Distance (m)
F 179 178.5 178 prior to removal
) 177.5 12/3/2007 m
( 177
n 12/20/2007 o
i 176.5 1/1/2008 176 evat l 2/23/2008 E 175.5 4/19/2008 175 174.5 174 0 102030 Distance (m)
Figure 31 (con’t.): (E) cross-section #5 (F) cross-section #6
88
179 G 178.5 178 prior to removal 177.5 12/3/2007 177 12/20/2007 176.5 1/1/2008 176 2/23/2008 Elevation (m) 175.5 4/19/2008 175 174.5 174 0 102030 Distance (m)
H 179 178.5 178 prior to removal
) 177.5 12/3/2007
(m 177
n 12/20/2007 o 176.5 ti
a 1/1/2008
v 176 e l 2/23/2008 E 175.5 4/19/2008 175 174.5 174 0102030 Distance (m)
Figure 31 (con’t.): (G) cross-section #7 (H) cross-section #8
89
179 I 178.5 178 177.5 177 prior to removal 176.5 2/23/2008 176 4/19/2008
elevation (m) 175.5 175 174.5 174 0 5 10 15 20 25 Distance (m)
J 179 178.5 178
) 177.5
(m 177 prior to removal n
o 176.5 12/20/2007 ti a
v 176 2/23/2007 e l
E 175.5 175 174.5 174 0102030 Distance (m)
Figure 31 (con’t.): (I) cross-section #9 (J) cross-section #10
90
179 K 178.5 178 177.5 prior to removal 177 12/20/2007 176.5 1/1/2008 176 2/23/2008
Elevation (m) Elevation 175.5 4/19/2008 175 174.5 174 0 5 10 15 20 25 Distance (m)
L 179 178.5 178 prior to removal
) 177.5 12/3/2007 m
( 177
n 12/20/2007 o
i 176.5 1/1/2008 176 evat l 2/23/2008 E 175.5 4/19/2008 175 174.5 174 0 102030 Distance (m)
Figure 31 (con’t.): (K) cross-section #11 (L) cross-section #12
91
179 M 178.5 178 177.5 prior to removal 177 12/3/2007 176.5 12/20/2007 176 1/1/2008
Elevation (m) 175.5 2/23/2008 175 174.5 174 0102030 Distance (m)
N 179 178.5 178 prior to removal
) 177.5 12/3/2007 m
( 177
n 12/20/2007 o
i 176.5 1/1/2008 176 evat l 2/23/2008 E 175.5 4/19/2008 175 174.5 174 0102030 Distance (m)
Figure 31 (con’t.): (M) cross-section #13 (N) cross-section #14
92
179 O 178.5 178 177.5 177 prior to removal 176.5 2/23/2008 176
elevation (m) 175.5 175 174.5 174 0 102030 Distance (m)
P 178.5
177.5 ) m (
n 176.5 prior to removal o i 2/23/2008
evat 175.5 el
174.5
173.5 0102030 Distance (m)
Figure 31 (con’t.): (O) cross-section #15 (P) cross-section #16
93
179 Q 178.5 178 177.5 177 prior to removal 176.5 2/23/2008 176 175.5 175 174.5
elevation above sea level (m) 174 0102030 Distance (m)
Figure 31 (con’t.): (Q) Cross section #17
94
then were preferentially destabilized and caused minor widening.
Downstream cross-sections also showed some changes in bed elevation as a result of the removal of the Secor dam (Figure 31 L-N). Sediment accumulation downstream of the former impoundment is most apparent at cross-section # 12 where a small mid- channel bar formed (Figures 31L). A single push core was extracted from the gravel bar.
Overall, the bar consisted of a thin veneer of poorly sorted, rounded, granule to coarse- grained quartz sand while the rest consisted of moderately sorted, rounded, fine- to medium-grained quartz sand. Cross-section #13 also showed bed aggradation on the west side of up to nearly 0.5 meters (Figures 31M). Further downstream, only trace amounts of sand accumulated behind large gravel clasts at cross section # 14 resulting in minimal changes in bed elevation (Figures 31N). In addition, approximately 30-m downstream of the former dam site, it was observed that some sandy sediment had accumulated within the deep pool at the confluence of Hill Ditch and the Ottawa River.
Week 4
By December 20 little additional incision and only minor widening had occurred in the former impoundment. Overall, the hydraulic geometry of the channels was much more uniform from one cross section to the next. For example, in the prior survey multiple small scours were noted between cross-sections #6 and #8, but by week four these have essentially been removed. The only scour that remained was located at cross- section #6 (Figure 31F). By week four, the entire area upstream consisted of a fluvial pavement except at cross-sections # 5 and #6 where the glacial-lacustrine sediment was exposed on the bed and was extensively tool-marked. Part of the pool adjacent to
95
meander bend one had aggraded slightly. Cross-section #8 was the only cross-section to show appreciable degradation (~0.4 centimeters) while the other upstream cross-sections have incised minor amounts (Figure 31H).
Downstream of the former dam, the mid-channel bar at cross-section #13 had eroded (Figure 30L). Cross-section #14 also degraded approximately 0.3-m since the last survey, while cross-section #15 showed little change in bed elevation (Figure 31M-N).
Week 6
On January 1 additional observations were made and nine cross-sections were
resurveyed. The most noticeable geomorphic adjustments occurred 46-m upstream of the former dam site, where slumping and bank erosion occurred on the west side of the
channel. The sediment that was mobilized during this event was not evident within the
adjacent channel and was likely transported downstream. The slump left a headwall
scarp along the west side of the channel. At meander bend 1, reworking of a sandy
deposit on the west side produced chute channel that was extensively rippled. No
appreciable incision or widening was noted from an examination of the cross-sections
surveyed.
Week 9
A large flood (~50 m3/sec) that occurred on January 11 resulted in significant
morphological changes of the former impoundment and reaches immediately downstream
of the former dam site. The significant flooding event resulted from a rainfall event in
which 3.13 centimeters of precipitation fell over the region over a period of 31 hours.
This rainfall event raised the stage height of the Ottawa River to above bankfull and
96
Figure 32: Photographs of slumping that occurred as a result of dam removal. (a) Meander bend 2 slumping. (b) Meander bend 1 slumping. See text for explanation.
97
resulted in nearly complete inundation of the floodplain. After the flood stage receded,
one of the most significant changes that was noted was a large slump that formed a near
vertical face on the inside of meander bend 2 between cross-sections # 8 and #10 (Figure
31H-I Figure 32a) . Additional slumping was also noted on the outside bend of the
meander bend 1 between cross-sections #2 and #3 (Figure 32b). This feature has
continued to widen since its initiation during the lowering of the water level in the
impoundment as a consequence of dam removal. This was likely caused by two phenomenon: (1) dam removal resulted in channel incision which acted to remove the toe
of the slump causing remobilization, and (2) slumps may be initiated from falling flood
stages due to bank storage, which may result in decreased strength of the sediment due to
a loss of cohesion.
The flood event caused appreciable channel widening near the former delta
(adjacent to cross-section #4). The flooding event caused incision of the former delta to a
depth of approximately 0.29 to 0.34-m, and widened the channel approximately one
meter at cross-section #4 (Figure 31D). The incision was again slowed by an organic-
rich silt and sand layer, (inundite facies), leaving a relatively flat topographic surface.
In the reaches immediately downstream of the former dam, a thin veneer of fine-
grained to medium-grained sand was deposited in a riffle sequence beneath the Secor
Bridge. The sandy layer covered portions of a riffle that previously had been a gravel to
cobble substrate. On the north side of the Ottawa River, sand was deposited both
overbank and in the area immediately adjacent to the north bank, with lesser amounts
being deposited in the center of the channel. Adjacent to the north side of the channel, as
much as 0.23-m of sand had accumulated as indicated by the penetration of a steel rod to
98
the maximum depth allowable.
Week 13
The next survey was completed on February 23 in which all 17 cross-sections
were resurveyed. The furthest upstream cross-sections (#1 and #2) were resurveyed and
have changed little as a result of the removal of the dam (Figure 31A-B). Cross-sections
#3-#7, which have been surveyed repeatedly, have changed very little from the last
survey (Figure 31B-G). Cross-section #8, however, widened appreciably from January
1st, especially on its west side (Figure 31H). A near-vertical slope now exists on the west side of the cross-section and all along the outside of meander bend 1 (Figure 31H).
Cross-sections #9 and #10 also showed channel widening on the west side from multiple slumping events as observed previously (figure 31I-J). Immediately downstream of the dam, cross-sections #12, #13, and #14 changed little from the last survey date.
The survey data upstream was then used to calculate the total volume of sediment removed as a result of dam removal by constructing a difference DEM (Figure 33) as described in the analysis of survey data sub-heading in the methods section. The results of the difference DEM indicated that between 487 m3 to 540 m3 (mean of 514 m3), of
primarily sand have been removed from behind the former Secor Dam. This was
determined by multiplying the depth of erosion of each pixel multiplied by the area of a
pixel. The difference DEM also shows areas of significant erosion as a result of dam
removal. Figure 33 shows that most of the incision that has occurred has been located in
the center of the channel while there has been relatively little erosion of the side of the
channel. The one exception is at meander bend 2 adjacent to cross-section # 7 where
99
Figure 33: DEM created to show the difference in elevation of the channel bed between the pre-removal channel and Feb 23, 2008 (approx. 3 months following dam removal).
100
there has been significant erosion which was caused by multiple slumping events in the
area. Figure 33 also depicts the large scour present at cross-section #6 that has widened
slightly through time (Figure 31f). Overall, the DEM provides an excellent way to view
the geomorphic adjustments caused by the removal of the Secor Dam.
Further downstream, cross sections #15 and #17 showed aggradation (~0.2-m) in
a portion of their cross sections while other parts of these cross sections degraded (Figure
31O,Q). The rest of the cross-section have changed little despite several large storm
events between the last survey. Additional fine- to medium-grained sand was also
deposited on the banks immediately downstream from the dam and also in the riffle
sequence immediately below the dam. Slight aggradation was also observed on four of
the downstream bars in the study area; a few centimeters of unconsolidated sand rested
on portions of each bar surface.
Week 21
The last survey was completed on April 19 in which 10 cross-sections were
resurveyed. Cross-section #3 showed slight widening from the last survey on its north
bank while the other cross-sections widened very little. Downstream of the dam there
were also relatively little changes in the surveyed cross-sections, although it was observed that sand had been deposited on several of the banks as a result of several high- stage height events. The most significant changes observed were on meander bends 1-2 where the slumps previously described have continued to grow (Figure 32a-b). The slump at meander bend-1 has continually grown on the cutbank (south) side of the meander (Figure 32b). The slump has continued to incise into the cutbank which is preferentially undermining a large tree (Figure 32b). The slump at meander bend 2
101
formed an escarpment 0.5-m in height and approximately 8.2-m in length. Adjacent to
the slump, several mud intraclasts derived from the former bank were measured with a
long axis ranging between 0.16 to 0.65-m. Just above cross-section #12, a large mud
intraclast was also observed with a long axis of approximately 1-m.
Bedload Measurements
Prior to and after the removal of the Secor Dam bedload measurements were collected to quantify any changes in sediment transport through time. Prior to dam removal, 11 bedload measurements were collected downstream of the dam at cross- section #14. These measurements revealed that essentially there was zero bedload transport which is attributed the high bedload trapping efficiency of the Secor dam. After the removal of the dam, bedload measurements were taken downstream at cross-section
#14 and upstream at cross-section # 4. Few bedload measurements could be taken after removal, however, due to perpetual high stage events and ice which resulted in relatively few data points (Figure 17a-b). Additionally, the low correlation coefficient of the bedload measurements may be due to the appreciable amount of bedload mobilized upstream during the first days of dam removal despite low flows. Even a removal of the zero Qs values, which acted as outliers in both data sets, failed to significantly improve the correlation coefficients (Figure 34a-b). Thus, only generalizations of the bedload data may be made.
The data collected upstream showed that immediately following dam removal a
large amount of substrate was mobilized during the first week, but during subsequent weeks as incision decreased there was a sharp decrease in the amount of bedload in transport (Table 4; Figure 35a). Downstream from the former dam, the bedload
102
a
10 y = -7E-06x + 4.5481 8 R2 = 0.2259
/s) 6 3
4 Q (m
2
0 0 1E-07 2E-07 3E-07 4E-07 5E-07 6E-07 7E-07
3 Qs (m /s)
b
6 5 4 /s)
3 y = 4E-07x + 2.5448 3 R2 = 0.1512
Q (m 2 1 0 0.00E+00 1.00E-08 2.00E-08 3.00E-08 4.00E-08 5.00E-08 6.00E-08
Qs (m3/s)
Figure 34: (a) Bedload data collected upstream after removal. (b) Bedload data collected downstream after dam removal. Note that all Qs values of zero are removed.
103
7.0E-07 a
6.0E-07
5.0E-07
4.0E-07
Qs (m3/s) 3.0E-07
2.0E-07
1.0E-07
0.0E+00 11/19 11/20 11/21 11/22 11/23 11/24 11/25 11/26 11/27 11/28 11/29 date of collection
6.0E-08 b
5.0E-08
4.0E-08
3.0E-08 Qs (m3/s)
2.0E-08
1.0E-08
0.0E+00 11/17 11/18 11/19 11/20 11/21 11/22 11/23 11/24 11/25 11/26 11/27 11/28 11/29 Date of collection Figure 35: (a) Graph depicting the change in sediment discharge through time upstream of the Secor dam. (b) Graph depicting the change in sediment discharge through time downstream of the Secor dam.
104
measurements collected was much more constant through time and showed in general
that with increasing discharge, there was more bedload transport (Table 4; Figure 35b).
DREAM modeling Results
The DREAM model predicted several areas of aggradation and degradation in the reaches immediately downstream and upstream of the Secor Dam. The zero process
(which used to ensure that the initial conditions of the model are adequate) revealed that the estimated pre-dam removal annual volume of bedload was too low and caused up to
15-cm of degradation in some of the downstream reaches. Thus the pre-dam removal bed load had to be increased to 150 m3 to produce quasi-equilibrium conditions downstream
of the dam site.
The model predicted that upon removal of the Secor dam, the bulk of the fluvial
adjustments would occur within the first week which agreed favorably with the actual
cross-section data. Cross-sections # 5 and #8 were expected to degrade their maximum
amount allowable (0.62 and 0.42 m, respectively) during the first twenty-four hours after
removal while cross-section # 10 was expected to degrade only 0.09 m (Figure 36a-c).
During day two the model predicted that cross-section # 10 would degrade an additional
0.44-m. No additional changes were predicted by the model upstream of the former dam for the rest of the 14-week simulation.
Downstream of the former Secor Dam the model predicted that cross sections #13 and #15 would aggrade 0.15 m and 0.03 m, respectively, during the first days following dam removal. During the next 6 weeks of simulation the model predicted that cross- sections #13, #15, #16, #17, and #18 would aggrade between 0.02 to 0.08 m, reaching a maximum at week seven. During week eight however, the DREAM-1 model predicted
105
that a large storm event from January 8-10, 2008 (Figure 9), would erode these cross-
sections back to their original bed elevation prior to removal. During the rest of the 14
week simulation there was no additional changes predicted by the DREAM-1 model.
Thus, the model predicted rapid incision to a maximum by day two followed by slight channel aggradation downstream which overall, largely agreed with the actual quantitative data collected after dam removal.
106
178.5 a
178
177.5
177 prior to removal 176.5 19-Nov
Elevation (m) 176
175.5
175 0 102030 channel width (m)
178.5 b
178
177.5
177 prior to removal 176.5 19-Nov
Elevation (m) 176
175.5
175 0 5 10 15 20 25 Channel Width (m)
Figure 36: Diagrams of bed elevation changes through time at cross-section # 5, # 8 and # 10. Note that after the first two days following removal the DREAM-1 model predicted no additional bed elevation changes. (a) cross-section #5. (b) cross-section #8
107
178.5 c
178
177.5 prior to removal 177 19-Nov 176.5 20-Nov
Elevation (m) 176
175.5
175 0 5 10 15 20 25 Channel Width (m)
Figure 36 (con’t.): (c) cross-section #10.
108
DISCUSSION
Cross-Section Data
The cross-section data provided a quantitative approach to access the geomorphic
adjustments following the removal of the Secor dam. The first two weeks following removal brought about significant incision into the former impoundment. As mentioned previously, incision ranged from approximately 0.3 m to 0.7 m. After initial rapid incision into the sandy material however relatively little changes in bed elevation were seen in the upstream cross-sections. The next two surveys (December 20, 2007 and
January 1, 2008) revealed very little changes upstream of the former impoundment. The survey of February 23, 2008, however, revealed that the former impoundment had begun to widen. Widening was apparent in cross-sections #8, #9, and #10 where the west banks were preferentially eroded away during a series of high discharge events during January and February (Figure 31 H-J). It is believed that the channel widening was caused by slumping events initiated by flooding events. The failure mechanism may have been caused by erosion of the toe of the slope by flooding which reactivated the slump.
Alternatively, undercutting the more cohesive organic-rich silt layer of the inundite facies may have caused the slumping. Most of the material that slumped into the channel was not visible after the high-flow events, suggesting rapid disaggregation and transport out of the study area. It is postulated that additional widening will take place in the future,
especially along the former delta which has been eroded intensely during previous
bankfull conditions and as widening slows the channel may also begin to aggrade.
109
Sediment Transport
Bedload measurements from the Helley-Smith bedload sampler revealed several
trends in the transport of bedload to the downstream reaches. First, the largest amount of
bedload was mobilized within the impoundment within the first few days (Table 4;
Figure 35a). Second, upstream of the former dam there was a significant decrease in the amount of bedload that occurred by week 2 (Figure 35a). Finally, comparison of the amount of bedload collected immediately upstream and downstream of the impoundment reveals that there must be a significant area of deposition between the sites where bedload is collected. It is apparent from Figure 37a-b that the coarser-grained material mobilized
upstream is being deposited prior to cross-section #15 (the site of downstream bedload
collection). It is postulated that this material may be deposited in two areas: (1)
immediately downstream (<30-m) from the former dam site or (2) the coarse-grained
material is being deposited in the pool opposite of meander bend 2.
The initial weeks after dam removal revealed little change in the surveyed reaches
immediately downstream despite high rates of bedload transport upstream of the former
Secor Dam. It is believed that despite relatively little changes to cross-sections #12 and
#13 this area may in fact have effectively trapped a significant amount of bedload. Prior
to dam removal, the channel bottom at these locations was extremely irregular due to a
large amount of angular cinder blocks and other large pieces of cement. It was observed
that there were significant void spaces in the bottom substrate. After the removal of the
Secor dam however, the bed become more uniform as these void spaces filled with sand.
Thus, these areas may have served as areas of significant deposition, although little
change was depicted in the survey data. Downstream, bed aggradation was observed at
110
a 80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
80 b 70 60
y 50 nc 40 que e 30 Fr 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Figure 37: Grain size distribution in whole phi increments of bedload collected on 11/29/07. Note that the coarser grain sizes (anything larger than 0Φ) was likely mobilized from the fluvial pavement facies. (a) Bedload data collected upstream. (b) Bedload data collected downstream. Note how the coarser grain sizes are not yet present in the downstream bedload data.
111
parts of cross sections #16 and #17, but other parts of these cross sections also degraded
slightly, with the result of no net sediment accumulation. Therefore, it is postulated that
sediment mobilized from upstream of the former dam was primarily deposited in the
riffle immediately downstream of the former dam, was deposited in a deep pool
approximately 30-m below the former dam, or the sediment was transported out of the
study area entirely.
The sandy sediment that was mobilized during the first hours after removal
translated downstream as a visible sediment wave, but after a storm event on November,
22 it was no longer visible. Although the sediment wave could have moved out of the
area as a consequence of flooding, it is hypothesized more likely it migrated into a pool at
meander bend two instead. Much of the sediment was subsequently eroded and
redeposited on the point bar. Doyle et al. (2003b) reports a similar possible response
when a sediment wave migrates into a depositional reach and then it may be decay in
place (i.e. disperse) or be redeposited elsewhere (continue to translate).
In summary, the bulk of the sediment mobilized during the initial stages of
geomorphic adjustments following the dam removal ended up in one of two places: either
in the pool approximately 30-m downstream at the confluence of the Ottawa River and
Hill Ditch or in the pool opposite the point bar (Figure 22). It appears that most of the
sediment can only be transported during high discharge events. This is evidenced by the
fact that little deposition of sand was noted prior to multiple flooding events that raised
the discharge of the Ottawa River to above bankfull conditions which may be another
consequence of the former dam impounding sandy sediment. Thus, only high flows
produce sufficient shear stress to overcome the critical shear stress to allow significant
112 amounts of materials to pass through this area without significant deposition. This is supported by the sediment routing calculation done by Gottgens et al. (2004) who stated that the downstream pool would serve as a sediment sink.
Comparison of the Secor Dam Removal to Other Removals
Field studies by various other researchers, such as and Doyle et al. (2003b) have developed a conceptual model for the response of a channel following dam removal
(Figure 38). Conceptual models of channel adjustments have been developed by several authors (e.g. Simon, 1989; Simon and Hupp, 1992), and it has been observed that the evolution of a channel following dam removal largely conform to these models (Doyle et al., 2003b). Doyle et al. (2003b) test their model by observing upstream channel formation and evolution following the removal of two small run-of-the-river dams
(Figure 38). In their model Stage A represents the pre-removal existing conditions. Stage
B represents the conditions immediately following dam removal, but prior to sediment mobilization. During stage C, initial channel incision begins. This is followed by Stage
D, which is characterized by continued incision and widening. During stage E, widening may continue as the channel begins to aggrade. Stage F marks the development of channel equilibrium and the establishment of vegetation over the former impoundment
(Doyle et al., 2003b; Figure 38). The duration of the six stages is highly variable; Pizzuto
(2002) states that the process may take decades while a study by Stanley et al. (2002) documented relatively small changes and rapid channel equilibrium development.
Evans (2007) tested the conceptual channel evolution model through a twelve year study of the IVEX dam removal in NE Ohio. The study demonstrated that the
113
Figure 38: Depiction of a channel evolution conceptual model following dam removal. The left model is from Doyle et al. (2003) while the right is the proposed modifications by Evans, (2007). Note the primary differences between the models are the initial stages of removal where Evans (2007) describes the formation of longitudinal furrows and the formation of an early breech drainage network during stages A and B (from Evans, 2007).
114
model proposed by Doyle et al. (2003b) correctly predicts the fluvial response of dam
removal. Evans (2007), however, modified the conceptual channel evolution model by
adding an initial stage of pre-failure reservoir erosion that resulted in the formation of
longitudinal scours, and the formation of an early-breach drainage network that grew by
nick point migration and was responsible for loss of the remaining storage capacity of the
reservoir (Evans, 2007).
Although the conceptual model proposed by Doyle et al. (2003b) provides a basic
framework of the evolution of channel following dam removal; it may not be fully
applied to all dam removals. The Doyle et al. (2003b) model was based on the study of impoundments that contained a significant portion of fine-grained material in the upper
portions near the dam, while upstream the deltaic deposits consisted of coarser-grained
sediment. The dams studied by Doyle et al., (2003b) also were filled to nearly full capacity by sediment. In contrast, the Secor dam primarily impounded fine-to medium- grained sand, with only relatively minor amounts of finer particles, and the upstream delta was composed of the same material as the rest of the impoundment. Additionally, the former reservoir had a well developed channel already existing prior to removal.
Thus, an evaluation of the geomorphic evolution of the Secor dam removal may provide
insight into the removal of dams that have primarily impounded sand-sized materials.
Despite the differences in the dams studied by Doyle et al. (2003b), the Secor dam responded to dam removal in a similar manner. Initially, following breaching of the dam
the incision was initiated (Stage C) and through time acted to destabilize the banks of the channel causing widening (Stage D). Although the conceptual model of Doyle et al.
(2003b) predicted the general response of the Secor dam removal, it differed on the
115
mechanisms that caused these geomorphic adjustments.
The channel evolution proposed by Doyle et al. (2003b) states that during the initial stages of removal (Stage C) incision into the former substrate is dominated by nick-point migration upstream through the former impoundment. In the case of the Secor dam removal however, only a diffuse, low-relief, nick-zone developed due to the unconsolidated sandy deposit. The nick-zone was not responsible for significant incision into the former impoundment primarily because the thickest deposits were located in a discrete zone between 62 and 83-m above the impoundment; thus the bed was already beginning to lower prior to the nick-zone reached this portion of the impoundment. It is hypothesized that the preexisting channel behind the former impoundment instead caused more uniform channel incision through the impoundment. This may be similar to the observations of Cheng and Granata (2007) in which the most significant sediment deposits were stored upstream in the impoundment and a well defined nick point failed to
develop. In fact, Moglen (2005) suggests the development of a nickpoint may be
uncommon when low-head dams are removed.
Thus, from the observations and quantitative data from the Secor dam removal, it
is suggested that it may be expected that sand-bedload rivers may respond to dam
removal through more uniform incision instead of nick-point migration. Gaeuman et al.
(2005) also documented this process from the examination of the geomorphology of the
Lower Duchesne River in Utah to varying sediment supply and discharge rates through
time, as a result various anthropogenic practices. Declining stream flows due to water
diversions and other land-use practices lead to bed aggradation due to the loss of its
sediment transport capacity. During a period of prolonged high flows, however, the river
116
began to reincise into the substrate narrowing the channel. Thus, it was suggested by
Gaeuman et al. (2005) that sand-bed rivers primarily respond to changes in geomorphic
conditions by bed-level changes, which agrees with the observations during the removal
of the Secor dam.
Another interesting geomorphic response during the initial hours following the
removal of the Secor dam was the narrowing of the main channel due to incision behind
the Secor dam. The process of erosional narrowing from bed degradation is well
documented in the literature (e.g. Surian and Rinaldi, 2003; Cantelli et al., 2007) and
commonly accompanies the first stages of bed degradation (Gaeuman et al., 2005).
Rapid erosional narrowing followed by slower channel widening has been described
previously in blow-and-go type removals by Cantelli et al., (2004) using multiple flume
experiments. Figure 30 illustrates a wider channel just prior to removal followed by
incisional narrowing two days after dam removal.
Thus, the channel evolution model developed by Doyle et al. (2003b) may need to be modified to more adequately describe the initial events of removal when a dam has primarily trapped sand, and a well defined channel is developed behind the impoundment prior to dam removal. Unlike the model proposed by Doyle et al. (2003b) incision occurred immediately throughout the former reservoir resulting in channel narrowing even though there was minimal discharge. This resulted in the mobilization of sand from the former delta as a sand wave. Within one week most incision was complete and the channel began to widen within a few weeks. Thus, this study suggests that the Ottawa
River adjusted at an accelerated rate due to the former Secor Dam only impounding non- cohesive sand. Lastly, it is suggested that dams that impound sand may not incise into
117
the former impoundment via nick-point migration but instead may degrade more
uniformly causing the channel to rapidly narrow (Stage C). This narrowing is then
followed by slower widening through time (Stage D). The slower widening process was
only documented in the series of cross sections collected 15 weeks after dam removal.
Cross sections #8, #9 and #10 have all underwent channel widening (Figure 31H-J).
Comparison of the Substrate of the Former and
Present Channel of the Ottawa River
It was determined through grain-size analysis that since the completion of the
Secor Dam in 1928, there have been changes in channel substrate. Substrates in the pre-
1928 channel have a mean grain size of +2 Ф while the mean grain size for the modern channel is +1Φ. Thus, the former channel was actually composed of a finer-grained substrate than the modern channel. This is attributed to the fluvial pavement facies that was present in the modern channel but was absent in the pre-1928 channel. With the exception of the fluvial pavement facies, both channel deposits contained the inundite facies, bioturbated facies, and cross-bedded sand facies.
It is postulated that the general increase presence of the fluvial pavement is a consequence of increasing urbanization in the basin. Grable and Harden (2006) have also reported a coarsening of the stream channel, but have primarily attributed the increased grain-size to the introduction of anthropogenic material (i.e. rip-rap, cinder blocks, trash, etc.) Although various large pieces of anthropogenic material were seen within the facies, most of the material was likely natural in origin. Wolman (1967) observed that construction activities caused increased sediment delivery rates, but following
118
construction with bare ground covered by pavement, buildings, or lawns and other
landscaping (i.e. urbanization), sediment input to streams decreased and channels
degraded due to the effects of flashy discharges and low sediment loads. It is has been
observed by the author that after rainfall events the discharge of the Ottawa River rises drastically. This rapid increase in discharge allows finer-grained material to be transported downstream while it acts to concentrate the coarser gravel lag deposits.
This was seen in real-time upon the removal of the Secor dam when some of the pavement was removed but subsequent storm events acted to re-establish an armored layer consisting of granule to pebble gravel with large bivalve shells.
Comparison of DREAM-1 with the Actual Data
Although the reaches immediately upstream and downstream of the dam site were greatly simplified, DREAM-1 adequately predicted the sediment that would be mobilized and deposited downstream. The volume of sediment that was predicted from the
DREAM-1 model was approximately 523 m3 of sediment as compared to 514 m3 which
was the average volume of sediment removed calculated from the difference DEM.
Thus, the volume of sediment removed predicted by the DREAM-1 model only differed
from the measured value by -1.7%. Downstream of the former dam DREAM-1 predicted
no net changes. Although the surveyed data appears to agree with these results;
significant deposition did occur immediately below the dam (at cross-sections #12 and
#13) through infiltration of sand into the large void spaces in the irregular anthropogenic
fill that comprised the bed of the channel. Further downstream however, at cross-
sections #14-#17 the model did adequately predict the resulting geomorphic adjustments.
119
Upstream of the former dam however, the DREAM model was unable to accurately predict the geomorphic adjustments at individual cross sections.
Due to the simplifications of the DREAM-1 model there were multiple differences between the model predictions and the actual results. As can be seen by a visual comparison of Figure 39a-c, the DREAM-1 model closely predicted the total incision that would occur at each cross section. However, the model failed to predict the channel widening that occurred at cross-sections #8 and #10 (Figure 39 a-c). As discussed previously, channel widening only occurs when the bottom width (Bm) of the upstream cross-section equals the bottom width of the downstream cross-section immediately adjacent to the former dam site. If these values are equal, the channel no longer incises but widens while maintaining the shape of the trapezoidal channel. The threshold above was never reached during the simulation period, however, so the model predicted no channel widening through time this in turn lead to under estimations of the total area removed from cross-sections #8 and #10 (Table 8; Figure 39 a-c).
Another simplification of the DREAM-1 model is assuming that the channel geometry is trapezoidal and that the side banks were at the angle of repose. This assumption may lead to appreciable errors if the bed configuration is irregular. For example, the model assumed that cross-section #5 would degrade uniformly (Figure 39a).
Due to the irregular nature of the bed however, cross-section #5 only degraded the former delta deposits on the south west side and eroded very little on the opposite bank (Figure
39a). This lead to a severe over-estimation of the total cross-sectional area removed
(Table 8). Despite being unable to accurately predict the geomorphic adjustments at each cross-section, the model did predict the total volume of sediment removed from the
120
179 a 178.5 178 177.5 177 simulated 176.5 observed 176 Elevation (m) 175.5 175 174.5 0 5 10 15 20 25 30 Channel Width (m)
179 b 178.5 178
) 177.5 (m
n 177 simulated o
ati 176.5 observed ev l 176 E 175.5 175 174.5 0 5 10 15 20 25 Channel Width (m)
Figure 39: Depiction of the surveyed changes upstream of the former dam at cross sections #5, #8, and #10 as compared to the changes predicted by the DREAM-1 model. (a) cross-section #5 (b) cross-section # 8.
121
178.5 c
178
177.5
177 simulated 176.5 observed
Elevation (m) 176
175.5
175 0 5 10 15 20 25 Channel Width (m)
Figure 39 (con’t.): (c) cross-section #10.
122 former impoundment within approximately 1.7%.
As demonstrated through a comparison with actual data DREAM-1 accurately predicted the volume of sediment released downstream and the areas of deposition, but the multiple simplifications of the model may complicate its use in certain situations. The removal of the Secor dam represents a rather simplistic case of dam removal; the impounded sediment was nearly homogenous and contained little clay to add bank cohesion, which would have slowed or greatly altered the predicted bed level changes following removal. Most removals that have been described in the literature have impounded a wide range of grain sizes (i.e. Doyle et al., 2003b; Stanley et al., 2002) and would likely require a model that can predict the sediment transport of a wide range of grain sizes. The model also failed to predict any channel widening; this is attributed to the assumption that widening only occurs after a maximum depth of incision is reached which is determined from downstream data. This assumption was not applicable for the case of the Secor dam removal because the thickness of impounded sediment was minute making the threshold that induces widening (Bm =Bb) unobtainable. Additionally, channel widening may not be dependent on the incision alone, it may be dependent on other factors such as the substrate of the former impoundment. As can be seen from this study additional research and development of more complex sediment transport models will likely be needed in the future to ensure that dam removal can be modeled adequately.
123
Table 8. Comparison of the predicted area removed from each cross- section compared to the actual calculated area removed Predicted area actual area x-section removed (m2) removed (m2) percent error (%) 10 7.4 9 -18.3 8 6.2 7.7 -19.5 5 13 6.7 92.5 total predicted area removed total actual area (m2) removed (m2) total error (%) 26.5 23.5 13.1
124
CONCLUSIONS
The removal of the Secor dam provided an excellent opportunity to study the fluvial response of a low-head dam that primarily impounded sandy material. Multiple channel surveys and field observations showed that the channel immediately incised and narrowed through nick-zone migration upstream into the former delta following dam removal. Incision continued for one week and was followed by slower widening through time via slumping of the banks through erosional processes.
It was determined through multiple channel surveys and other data collected prior to and after the removal of the Secor Dam that the initial stages of channel evolution proposed by Doyle et al., (2003b) may not be applicable to the removal of dams that act to accumulate predominantly sand and accumulated little sediment through time. It has instead been proposed that during the initial stages of removal more uniform rates of bed incision will be expected instead of the formation of a prominent nick point that may form in more cohesive sediments. Immediately downstream of the former dam, bed elevation changes were restricted to a deep pool 30-m downstream. However, additional deposition of sand occurred due to the infiltration of sand into the coarse, irregular anthropogenic substrate making the channel bed more uniform without producing any bed elevation changes. Further downstream, any changes that occurred were primarily attributed to a series of high stage height events that acted to mobilize sand downstream.
Prior to these events however, most sediment was deposited the coarse anthropogenic substrate immediately downstream from the dam or in a deep pool approximately 30-m downstream which served as a sediment sink, and or the bulk of the sediment was
125 deposited within the reservoir in the pool opposite the point bar deposit at meander bend
2. Thus, the study indicates that dams that impound sand may undergo geomorphic adjustments at an accelerated rate and may only transport sediment downstream during high stage events.
As has been demonstrated, DREAM-1 provides a good estimate of the expected volume of sediment that will be mobilized and deposited downstream following dam removal. It may only be applied during the initial stages of removal however because it can only predict incision; in cases where incision may be minor and channel widening may be the dominate process by which the fluvial system adjusts, then the model may greatly underestimate the resulting geomorphic adjustments. Thus, the use of the
DREAM suite of models may only be applied on a dam specific basis and decision makers should be informed of the inherent simplifications of the model. In conclusion, the removal of the Secor Dam has provided additional insight into the geomorphic response of dam removal. A comprehensive study of the impoundment prior to removal and the resulting adjustments have allowed for a large database of information which may be used by future modelers to test the validity of new models which may aid in the science of dam removal.
126
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APPENDICES 132
APPENDIX A
TOTAL STATION SETUP 133
The Top Con Total station was used to survey all channel cross sections. Unlike
the use of an optical transit, the total station performs the trigonometric calculations for
each surveyed point in real-time. All data was collected in the coordinate system mode,
meaning that each point was described in the x, y and z direction (northing, easting, and
z). Upon securing the tripod, the total station was attached and leveled. The first piece of
data that must be entered into the total station is a compass direction that serves as a
reference direction for all future surveys. The compass direction entered may be any
direction but must be the same for all occupied points so that the data is all defined by the
same coordinate system. For the purposes of this surveying exercise, true North was
chosen as the reference direction. A Brunton Compass was used to determine the
direction of true north. A reference stake was then placed at each occupied point so that
all future measurements would have the same input angle. Next the height of the instrument and the height of the reflector were input into the total station; these measurements are important because the trigonometric calculations are based on the input data. Lastly, the occupied point must be described in the x, y and z direction. Occupied point 1, from which all surveys was based, was determined by using a differential GPS unit on multiple occasions to determine the location of this point. The total station was then used for data collection.
When the total station needed to be moved to a different location to continue surveying, a back sight point had to be shot to the new location. The back sight point may be collected two ways: (1) It may be simply collected by collecting the point and inputting it manually as the next occupied point in the coordinate mode, or (2) in data collection mode you may select back sight mode which will save the new occupied point 134 for future use. The new occupied points determined from these methods were then marked with a reference stake for future surveys. During subsequent surveys a plum bob was used to ensure that the total station was directly over the reference stake at each occupied point. 135
APPENDIX B
SEDIMENT PUSH CORES 136
Figure B: Note that sections are oriented so that you are looking downstream. Stratigraphic sections that are missing were surface samples or could not be obtained. Note that surface samples were collected at all locations for cross-sections #12 and #15. (1) Stratigraphic section of cross-section #1. 137
Figure B continued: (2) Stratigraphic section of cross-section #2. 138
Figure B continued: (3) Stratigraphic section of cross-section #3. 139
Figure B Continued: (4) Stratigraphic section of cross-section #4. 140
Figure B Continued: (5) Stratigraphic section of cross-section #5. 141
Figure B Continued: (6) Stratigraphic section of cross-section #6. 142
Figure B Continued: (7) Stratigraphic section of cross-section #10.
143
Figure B Continued: (8) Stratigraphic section of cross-section #11.
144
Figure B Continued: (9) Stratigraphic section of cross-section #16.
145
APPENDIX C
BEDLOAD GRAINSIZE STATISTICS
146
11/20/07 upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/20/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.90 -0.75 0.03 0.98 1.60 1.80 2.40
mode median mean SD S K 2.0 Φ 0.98 Φ 0.68 Φ 1.29 Φ -0.35 Φ 1.12 Φ
Figure C1: Plots of cumulative weight percent versus grain size for each upstream bedload sample along with a histogram of the grain size distribution for each bedload measurement taken upstream after removal of the Secor Dam.
147
11/20/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/20/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.00 0.00 0.55 1.06 1.62 1.83 2.60
mode median mean SD S K 2.0Φ 1.06 Φ 0.96 Φ 1.00 Φ -0.15 Φ 1.38 Φ
Figure C1: Continued
148
11/21/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -5 -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/21/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.00 -3.52 -3.20 -1.32 1.13 1.50 2.48
mode median mean SD S K -3.0 Φ -1.32 Φ -1.11 Φ 2.24 Φ 0.15 Φ 0.61Φ
Figure C1: Continued
149
11/22/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/22/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.60 -1.65 -1.00 -1.41 1.50 1.78 2.35
mode median mean SD S K 2.0 Φ -1.41 Φ -0.43 Φ 1.61 Φ 0.69 Φ 0.81 Φ
Figure C1: Continued
150
11/24 upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/24/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.10 -2.59 -2.21 -1.39 -0.25 0.50 1.80
mode median mean SD S K -1.0 Φ -1.39 Φ -1.16 Φ 1.51 Φ 0.26 Φ 1.03 Φ
Figure C1: Continued
151
11/26/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -5 -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/26/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.19 -3.50 -3.04 -1.00 -1.37 1.62 2.00
mode median mean SD S K 2.0 Φ -1.00 Φ -0.96 Φ 2.22 Φ 0.00 Φ 1.52 Φ
Figure C1: Continued
152
11/27/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/27/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.60 -2.80 -2.60 -1.30 1.10 1.50 2.47
mode median mean SD S K -2.0 Φ -1.30 Φ -0.87 Φ 2.00 Φ 0.27 Φ 0.67 Φ
Figure C1: Continued
153
11/29/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/29/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.50 -0.50 0.10 1.05 1.62 1.80 2.50
mode median mean SD S K 2.0 Φ 1.05 Φ 0.78 Φ 1.18 Φ -0.31 Φ 1.08 Φ
Figure C1: Continued
154
12/20/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
12/20/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.00 -1.25 -0.56 1.25 1.75 1.96 2.75
mode median mean SD S K 2.0 Φ 1.25 Φ 0.65 Φ 1.52 Φ -0.46Φ 0.84Φ
Figure C1: Continued
155
12/20/07 Upstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
12/20/07 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.00 -1.25 -0.56 1.25 1.75 1.96 2.75
mode median mean SD S K 2.0Φ 1.25Φ 0.65Φ 1.52Φ -0.46Φ 0.84Φ
Figure C1: Continued
156
1/17/07 Upstream
100
80
60
40
20
Cumulative Weight PercentCumulative Weight 0 -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
1/17/08 Upstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.75 -3.18 -2.75 -1.50 0.27 0.57 1.13
mode median mean SD S K 1.0 -1.50 -1.37 1.68 0.09 0.66
Figure C1: Continued
157
11/19/07 Downstream
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -5 -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/19/ 07 Downstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.90 -4.65 -4.26 -3.81 -1.50 0.70 2.31
mode median mean SD S K -4.0 Φ -3.81 Φ -2.59 Φ 2.43 Φ 0.69 Φ 1.07 Φ
Figure C2: Plots of cumulative weight percent versus grain size for each downstream bedload sample along with a histogram of the grain size distribution for each bedload measurements taken downstream after removal of the Secor Dam.
158
11/20/07 Downstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/20/07 Downstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.75 -0.55 0.20 1.25 1.75 2.10 2.75
mode median mean SD S K 2.0 Φ 1.25 Φ 0.93 Φ 1.34 Φ -0.35 Φ 1.19 Φ
Figure C2: Continued
159
11/24/07 Downstream
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/24/07 Downstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.49 -2.25 -1.75 0.91 1.82 2.23 2.81
mode median mean SD S K 2.0 Φ 0.91 Φ 0.30 Φ 2.07 Φ -0.40 Φ 0.72 Φ
Figure C2: Continued
160
11/26/07 Downstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/26/07 Downstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.60 0.75 1.18 1.82 2.50 2.75 3.01
mode median mean SD S K 0.0 Φ 1.82 Φ 1.77 Φ 1.35 Φ -0.32 Φ 1.74 Φ
Figure C2: Continued
161
11/29/07 Downstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
11/29/07 Downstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.00 1.25 1.47 2.07 2.51 2.71 2.90
mode median mean SD S K 3.0 Φ 2.07 Φ 2.01 Φ 0.65 Φ -0.12 Φ 0.75 Φ
Figure C2: Continued
162
1/17/07 Downstream
100
80
60
40
20
0 Cumulative Weight Percent Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 <4 Phi Size Class
1/17/08 Downstream
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.20 -2.35 -1.65 1.04 1.75 2.05 2.75
mode median mean SD S K 2.0 Φ 1.04 Φ 0.25 Φ 2.00 Φ -0.48 Φ 0.72 Φ
Figure C2: Continued
163
APPENDIX D
CORE GRAINSIZE STATISTICS 164
Cross-Section #1 Left (7-10.5 cm)
100 80 60 40 20 0 -4 -2 0 24
Cumulative Weight Percent Phi Size Class
Cross-Section #1 Left (7-10.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.87 -0.38 0.22 1.30 2.20 2.69 4.26
mode median mean SD S K 2.0 Φ 1.30 Φ 1.20 Φ 1.70 Φ -0.06 Φ 1.27 Φ
Figure D1: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #1 along with a histogram for each site. 165
Cross-Section #1 Left (11-13.5 cm)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #1 Left (11-13.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.60 -2.98 -0.73 1.69 3.10 3.57 5.35
mode median mean SD S K 3.0 Φ 1.69 Φ 0.76 Φ 3.15 Φ -0.35 Φ 1.06 Φ
Figure D1: continued 166
Cross-Section # 1 Left (34-37.5cm)
100 80 60 40 20 0 -4 -2 0 2 4 6
Cumulative Weight Percent Phi Size Class
Cross-Section # 1 Left (34-37.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.05 0.63 1.06 1.50 1.92 2.45 2.73
mode median mean SD S K 3.0 Φ 1.50 Φ 1.53 Φ 0.86 Φ -0.02 Φ 1.28 Φ
Figure D1: continued
167
Cross-Section # 1 Center (surface sample)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #1 (surface Sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.80 -4.40 -4.06 -3.00 0.31 1.23 2.10
mode median mean SD S K -4.0 Φ -3.00 Φ -2.06 Φ 2.45 Φ 0.49 Φ 0.65 Φ
Figure D1: continued
168
Cross-Section #1 Right (5-8.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #1 Right (5-8.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.80 -3.40 -3.05 -1.50 1.20 1.78 2.90
mode median mean SD S K -3.0 Φ -1.50 Φ -1.04 Φ 2.31 Φ 0.29 Φ 0.65 Φ
Figure D1: continued
169
Cross-Section #1 Right (22-25.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #1 Right (22-25.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -0.50 0.28 0.60 1.31 1.90 2.40 3.77
mode median mean SD S K 2.0 Φ 1.31 Φ 1.33 Φ 1.18 Φ 0.09 Φ 1.34 Φ
Figure D1: continued
170
Cross-Section #2 Left (15-29 cm)
100 80 60 40 20
0 -4 -2 0 2 4 6
Cumulative Weight Percent Phi Size Class
Cross-Section # 2 Left (15-29 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.15 1.10 1.70 3.10 4.21 4.59 5.00
mode median mean SD S K 0.0 Φ 3.10 Φ 2.93 Φ 1.61 Φ -0.18 Φ 0.79 Φ
Figure D2: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #2 along with a histogram for each site.
171
Cross-Section #2 Center (11-24 cm)
100 80 60 40 20
0 -4 -2 0 2 4 6
Cumulative Weight Percent Phi Size Class
Cross-Section #2 Center (11-24 cm)
80 70 60 50 40 30 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.15 -0.83 -0.10 1.11 2.89 3.80 5.32
mode median mean SD S K 1.0 Φ 1.11 Φ 1.36 Φ 2.29 Φ 0.14 Φ 1.02 Φ
Figure D2: continued
172
Cross-Section #2 Right (0-14 cm)
100 80 60 40 20
0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #2 Right (0-14 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.20 1.00 1.24 1.89 2.83 3.40 4.46
mode median mean SD S K 2.0 Φ 1.89 Φ 2.10 Φ 1.25 Φ 0.23 Φ 1.10 Φ
Figure D2: continued 173
Cross-Section # 3 Left (0-14.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent -4 -2 0 2 4 6 Phi Size Class
Cross-Section #3 Left (0-14.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.51 1.32 1.70 2.50 3.40 3.82 4.58
mode median mean SD S K 3.0 Φ 2.50 Φ 2.55 Φ 1.24 Φ 0.04 Φ 0.98 Φ
Figure D3: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #3 along with a histogram for each site.
174
Cross-Section #3 Center (17-32 cm)
100 80 60 40 20
0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #3 Center (17-32 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.60 1.60 -1.00 0.80 1.88 2.41 3.80
mode median mean SD S K 2.0 Φ 0.80 Φ 1.60 Φ 1.17 Φ 1.45 Φ 0.91 Φ
Figure D3: continued 175
Cross-Section #3 Right (0-14.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent -4 -2 0 2 4 Phi Size Class
Cross-Section #3 Right (0-14.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.40 1.00 1.57 2.40 2.89 3.44 4.47
mode median mean SD S K 3.0 Φ 2.40 Φ 2.28 Φ 1.50 Φ -0.22 Φ 1.82 Φ
Figure D3: continued
176
Cross-Section #4 Left (23-26.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #4 Left (23-26.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.30 1.17 1.40 2.05 2.70 2.87 3.89
mode median mean SD S K 3.0 Φ 2.05 Φ 2.03 Φ 0.97 Φ -0.01 Φ 1.13 Φ
Figure D4: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #4 along with a histogram for each site.
177
Cross-Section #4 Center (0-6 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #4 Center (0-6 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.54 -2.75 -2.27 -1.07 0.91 1.70 3.31
mode median mean SD S K 1.0 Φ -1.07 Φ -0.71 Φ 2.15 Φ 0.26 Φ 0.88 Φ
Figure D4: continued
178
Cross-Section # 4 Center (15.4-19 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #4 Center (15.4-19 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.56 -2.73 -2.23 -1.10 0.93 1.70 3.20
mode median mean SD S K -1.0 Φ -1.10 Φ -0.71 Φ 2.13 Φ 0.27 Φ 0.88 Φ
Figure D4: continued
179
Cross-Section #4 Center (60-63.5)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #4 Center (60-63.5 cm)
35 30 25 20 15
Frequency 10 5 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.62 1.45 1.59 2.42 3.43 3.92 4.70
mode median mean SD S K 3.0 Φ 2.42 Φ 2.60 Φ 1.24 Φ 0.17 Φ 0.91 Φ
Figure D4: continued
180
Cross-Section #4 Right (42-45.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #4 Right (42-45.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.90 1.00 1.20 1.59 1.93 2.31 4.00
mode median mean SD S K 2.0 Φ 1.59 Φ 1.63 Φ 0.80 Φ 0.33 Φ 1.74 Φ
Figure D4: continued
181
Cross-Section #5 Left (8-11.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #5 Left (8-11.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 234 56 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.20 1.37 1.92 2.87 4.10 4.40 4.81
mode median mean SD S K 3.0 Φ 2.87 Φ 2.88 Φ 1.46 Φ -0.07 Φ 0.87 Φ
Figure D5: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #5 along with a histogram for each site.
182
Cross-Section #5 Left (28-31.5 cm)
100 80 60 40 20 0 -5 -3 -1 135 Cumulative Weight Percent Phi Size Class
Cross-Section #5 Left (28-31.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 012345 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.41 -2.41 -1.74 0.33 1.71 2.20 3.60
mode median mean SD S K 2.0 Φ 0.33 Φ 0.04 Φ 2.21 Φ -0.13 Φ 0.83 Φ
Figure D5: continued
183
Cross-Section #5 Center (12-15.5 cm)
100 80 60 40 20
0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #5 Center (12-15.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.00 1.42 1.85 2.40 2.89 3.20 4.27
mode median mean SD S K 2.0 Φ 2.40 Φ 2.34 Φ 0.94 Φ 0.02 Φ 1.29 Φ
Figure D5: continued
184
Cross-Section #5 Center (27-30.5 cm)
100 80 60 40 20 0 -4 -2 0 246 Cumulative Weight Percent Phi Size Class
Cross-Section #5 Center (27-30.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 012345 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.07 1.24 1.40 1.79 2.31 2.40 2.87
mode median mean SD S K 3.0 Φ 1.79 Φ 1.81 Φ 0.56 Φ 0.13 Φ 0.81 Φ
Figure D5: continued
185
Site # 5 Right (3-7.5 cm)
100
80
60
40
20
0 Cumulative weight percent weight Cumulative -5 -3 -1 1 3 5 7 Phi Size Class
Site # 5 Right (3-7.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.21 -3.40 -2.80 -1.30 1.26 1.98 3.00
mode median mean SD S K -2.0 Φ -1.30 Φ -0.91 Φ 2.44 Φ 0.21 Φ 0.73 Φ
Figure D5: continued
186
Site # 5 Right (26-29.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 6 Phi Size Class
Site # 5 Right (26-29.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -0.79 0.90 0.38 1.29 1.80 2.20 4.11
mode median mean SD S K 2.0 Φ 1.29 Φ 1.46 Φ 1.07 Φ 0.28 Φ 1.42 Φ
Figure D5: continued
187
Site # 5 Right (40-43.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 6 Phi Size Class
Site # 5 Right (40-43.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.00 -1.90 -1.43 -0.31 1.00 1.86 4.00
mode median mean SD S K 0.0 Φ -0.31 Φ -0.12 Φ 2.00 Φ 0.19 Φ 1.18 Φ
Figure D5: continued
188
Cross-Section #9 Left (15-30cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Left (15-30 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -0.32 0.77 1.23 2.25 3.30 3.79 4.51
mode median mean SD S K 3.0 Φ 2.25 Φ 2.27 Φ 1.49 Φ -0.02 Φ 0.96 Φ
Figure D6: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #9 along with a histogram for each site.
189
Cross-Section #9 Center (0-15 cm)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Center (0-15 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.80 -4.39 -4.02 -2.10 -0.30 1.07 2.31
mode median mean SD S K -4.0 Φ -2.10 Φ -1.81 Φ 2.44 Φ 0.20 Φ 0.78 Φ
Figure D6: continued
190
Cross-Section #9 Center (26.5-38.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Center (26.5-38.5 cm)
35 30 25 20 15
Frequency 10 5 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.10 0.14 0.90 2.10 3.31 3.62 4.05
mode median mean SD S K 4.0 Φ 2.10 Φ 1.95 Φ 1.95 Φ -0.29 Φ 1.22 Φ
Figure D6: continued
191
Cross-Section #9 Center (38.5-52.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Center (38.5-52 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.10 1.80 2.20 3.20 3.70 3.90 4.59
mode median mean SD S K 4.0 Φ 3.20 Φ 2.97 Φ 1.05 Φ -0.27 Φ 0.95 Φ
Figure D6: continued
192
Cross-Section #9 Right (2-10.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Right (2-10.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.31 -2.62 -2.25 -1.20 0.80 1.42 2.40
mode median mean SD S K -1.0 Φ -1.20 Φ -0.80 Φ 1.88 Φ 0.28 Φ 0.77 Φ
Figure D6: continued
193
Cross-Section #9 Right (20-34.1 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Right (20-34.1 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.40 -0.50 0.08 0.87 1.60 1.81 2.80
mode median mean SD S K 2.0 Φ 0.87 Φ 0.73 Φ 1.21 Φ -0.13 Φ 1.13 Φ
Figure D6: continued
194
Cross-Section #9 Right (34.1-48.4)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Right (34.1-48.4)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.63 -0.40 0.13 1.03 2.69 1.90 3.48
mode median mean SD S K 2.0 Φ 1.03 Φ 0.84 Φ 1.35 Φ -0.14 Φ 0.82 Φ
Figure D6: continued
195
Cross-Section #9 Right (49.4-62.4 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 Right (49.4-62.4 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.65 1.19 1.32 1.81 2.62 2.95 4.40
mode median mean SD S K 2.0 Φ 1.81 Φ 1.98 Φ 1.01 Φ 0.34 Φ 1.18 Φ
Figure D6: continued
196
Cross-Section #9 (70.5-84.8 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #9 (70.5-84.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.88 -0.38 0.24 1.30 2.20 2.75 4.20
mode median mean SD S K 2.0 Φ 1.30 Φ 1.22 Φ 1.70 Φ -0.06 Φ 1.27 Φ
Figure D6: continued
197
Cross-Section #10 Center (8-22 cm)
100 80 60 40 20
0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #10 Center (8-22 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.12 0.04 0.83 2.30 3.78 4.29 4.78
mode median mean SD S K 3.0 Φ 2.30 Φ 2.21 Φ 1.96 Φ -0.11 Φ 0.82 Φ
Figure D7: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #10 along with a histogram for each site.
198
Cross-Section #10 Center (52-66cm)
100 80 60 40 20
0 -4 -2 0 2 4 6
Cumulative Weight Percent Phi Size Class
Cross-Section #10 Center (52-66 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.00 1.40 1.73 2.40 3.00 3.61 4.50
mode median mean SD S K 3.0 Φ 2.40 Φ 2.47 Φ 1.08 Φ 0.15 Φ 1.13 Φ
Figure D7: continued
199
Cross-Section #10 Right (30-45 cm)
100 80 60 40 20
0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #10 Right (30-45 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -0.27 0.40 0.73 1.43 2.40 3.09 3.81
mode median mean SD S K 2.0 Φ 1.43 Φ 1.64 Φ 1.29 Φ 0.20 Φ 1.00 Φ
Figure D7: continued
200
Cross-Section #10 Right (45-60 cm)
100 80 60 40 20
0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #10 Right (45-60 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.71 -1.16 0.42 1.75 2.86 3.70 4.50
mode median mean SD S K 3.0 Φ 1.75 Φ 1.43 Φ 2.31 Φ -0.22 Φ 1.21 Φ
Figure D7: continued
201
Cross-Section #11 Left (33-47 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #11 Left (33-47 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.21 1.87 2.13 2.61 3.45 4.00 4.70
mode median mean SD S K 3.0 Φ 2.61 Φ 2.83 Φ 1.06 Φ 0.25 Φ 1.08 Φ
Figure D8: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #11 along with a histogram for each site.
202
Cross-Section #11 Center (0-14.4 cm)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #11 Center (0-14.4 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.78 -4.21 -3.79 -2.40 -0.42 0.50 2.00
mode median mean SD S K -4.0 Φ -2.40 Φ -2.04 Φ 2.20 Φ 0.26 Φ 0.82 Φ
Figure D8: continued
203
Cross-Section #11 Center (14.4-28 cm)
100 80 60 40 20 0 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Cumulative Weight Percent Phi Size Class
Cross-Section #11 Center (14.4-28cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.50 0.87 1.28 1.88 2.90 3.78 5.50
mode median mean SD S K 2.0 Φ 1.88 Φ 2.18 Φ 2.24 Φ 0.01 Φ 2.53 Φ
Figure D8: continued
204
Cross-Section # 11 Right (23.5-35.5 cm)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section # 11 Right (23.5-35.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.39 1.20 1.59 2.70 3.68 4.06 4.70
mode median mean SD S K 4.0 Φ 2.70 Φ 2.65 Φ 1.37 Φ -0.06 Φ 0.85 Φ
Figure D8: continued
205
Cross-Section #12 Left (surface sample)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #12 Left (surface sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.50 -1.51 -1.00 -0.30 0.43 0.71 1.35
mode median mean SD S K 0.0 Φ -0.30 Φ -0.37 Φ 1.14 Φ -0.12 Φ 1.10 Φ
Figure D9: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #12 along with a histogram for each site.
206
Cross-Section #12 Center (surface sample)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #12 Center (surface sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.74 -1.83 -1.54 -0.78 -0.08 0.38 0.94
mode median mean SD S K 0.0 Φ -0.78 Φ -0.74 Φ 1.11 Φ -0.01 Φ 1.03 Φ
Figure D9: continued
207
Cross-Section # 12 Right (surface sample)
100 80 60 40 20 0 -4 -2 0 2 4
Cumulative Weight Percent Phi Size Class
Cross-Section #12 Right (surface sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.10 -2.40 -1.96 -1.00 -0.18 0.30 0.91
mode median mean SD S K 0.0 Φ -1.00 Φ -1.03 Φ 1.28 Φ -0.04 Φ 0.92 Φ
Figure D9: continued
208
Cross-Section #15 Left (surface sample)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #15 Left (surface sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.72 -4.20 -3.81 -2.94 -0.52 1.09 1.92
mode median mean SD S K -3.0 Φ -2.94 Φ -2.02 Φ 2.33 Φ 0.49 Φ 0.83 Φ
Figure D10: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #15 along with a histogram for each site.
209
Cross-Section #15 Center (surface sample)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #15 Center (surface sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.85 -4.47 -4.17 -3.16 0.00 1.26 1.73
mode median mean SD S K -4.0 Φ -3.16 Φ -2.12 Φ 2.43 Φ 0.51 Φ 0.65 Φ
Figure D10: continued
210
Cross-Section #15 Right (surface sample)
100 80 60 40 20 0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #15 Right (surface sample)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.95 -4.60 -4.58 -3.34 0.83 1.34 1.97
mode median mean SD S K -4.0 Φ -3.34 Φ -2.20 Φ 2.53 Φ 0.56 Φ 0.52 Φ
Figure D10: continued
211
Cross-Section #17 Left (4-18.2 cm)
100 80 60 40 20
0 -5 -3 -1 1 3 5
Cumulative Weight Percent Phi Size Class
Cross-Section #17 Left (4-18.2 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.69 -0.71 -0.31 0.83 2.60 3.32 4.61
mode median mean SD S K 0.0 Φ 0.83 Φ 1.15 Φ 1.96 Φ 0.22 Φ 0.89 Φ
Figure D11: Plots of cumulative weight percent versus grain size for each push core collected from cross-section #17 along with a histogram for each site.
212
Cross-Section #17 Center (0-10.5 cm)
100 80 60 40 20
0 -4 -2 0 2 4 6
Cumulative Weight Percent Phi Size Class
Cross-Section #17 Center (0-10.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.41 1.39 1.85 1.69 3.69 4.12 4.95
mode median mean SD S K 3.0 Φ 1.69 Φ 2.40 Φ 1.37 Φ 0.61 Φ 1.01 Φ
Figure D11: continued 213
Cross-Section #17 Right (0-14.5 cm)
100 80 60 40 20
0 -4 -2 0 2 4 6
Cumulative Weight Percent Phi Size Class
Cross-Section #17 Right (0-14.5 cm)
80 70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -1.68 -1.76 -0.31 1.19 2.79 3.56 5.60
mode median mean SD S K 0.0 Φ 1.19 Φ 1.00 Φ 2.43 Φ 0.05 Φ 0.97 Φ
Figure D11: continued
214
07-OR-01 (114-117 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -5 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
07-OR-01 (114-117 cm)
35 30 25 20 15
Frequency Frequency 10 5 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -0.2 1.5 1.4 2.2 3.2 4.0 4.6
mode median mean SD S K 2Ф 2.2Ф 2.6Ф 1.4Ф 0.21Ф 1.1Ф
Figure D12: Plots of cumulative weight percent versus grain size along with a histogram depicting the grain size distribution for each vibracore collected from the former Ottawa River.
215
07-OR-01 (135-139 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 6 Phi Size Class
07-OR-01 (135-139 cm)
60
50
40
30 20 Frequency 10
0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.1 -1.3 0.2 1.3 1.8 2.0 3.5
mode median mean SD S K 2.0 Ф 1.3 Ф 0.7 Ф 1.7 Ф -0.4 Ф 1.4 Ф
Figure D12: Continued 216
07-OR-03 (125-129 cm)
100
80
60
40 Percent
20 Cumulative Weight 0 -4 -2 0 2 4 Phi Size Class
07-OR-03 (125-129 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.1 1.2 1.36 1.68 2.1 2.61 4.1
mode median mean SD S K 2Ф 1.7 Ф 1.8 Ф 0.8 Ф 0.5 Ф 1.7 Ф
Figure D12: Continued
217
07-OR-03 (140-144 cm)
100
80
60
40
20 Cumulative Percent 0 -4 -2 0 2 4 Phi Size Class
07-OR-03 (140-144)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.2 1.0 1.2 1.3 1.8 1.9 2.9
mode median mean SD S K 2.0 Ф 1.3 Ф 1.4 Ф 0.6 Ф 0.3 Ф 1.7 Ф
Figure D12: Continued
218
07-OR-03 (152-156 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 6 Phi Size Class
07-OR-03 (152-156 cm)
25
20
15
10 Frequency 5
0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -2.0 -1.0 -0.3 1.3 2.7 3.5 4.9
mode median mean SD S K 2.0 Ф 1.26 1.26 Ф 2.16 Ф 0.03 Ф 0.96 Ф
Figure D12: Continued
219
07-OR-03 (166-169 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 6 Phi Size Class
07-OR-03 (166-169)
35 30 25 20 15
Frequency 10 5 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -0.4 0.4 0.9 1.7 2.8 3.5 4.5
mode median mean SD S K 2.0 Ф 1.7 Ф 1.9 Ф 1.5 Ф 0.1 Ф 1.0 Ф
Figure D12: Continued
220
07-OR-04 (143-147 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 6 Phi Size Class
07-OR-04 (143-147)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.1 1.6 2.1 2.8 3.8 4.3 4.8
Mode median mean SD S K 3.0 Ф 2.83 Ф 2.76 Ф 1.11 Ф 0.08 Ф 0.86 Ф
Figure D12: Continued
221
07-OR-04 (170-174 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -2 0 2 4 Phi Size Class
07-OR-04 (170-174 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -3.30 -2.62 -2.30 -1.20 0.80 1.41 2.45
mode median mean SD S K 2.0 Ф -1.20 Ф -0.80 Ф 1.88 Ф 0.28 Ф 0.76 Ф
Figure D12: Continued
222
07-OR-06 (116-120 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
07-OR-06 (116-120)
50
40
30
20 Frequency 10
0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.1 1.4 1.6 2.3 2.8 3.2 4.5
mode median mean SD S K 3.0 Ф 2.3 Ф 2.3 Ф 1.0 Ф 0.1 Ф 1.2 Ф
Figure D12: Continued
223
07-OR-06 (134-138 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
07-OR-06 (134-138 cm)
70 60 50 40 30
Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.2 1.7 2.1 2.5 2.9 3.1 4.2
mode median mean SD S K 3.0 Ф 2.48 Ф 2.43 Ф 0.79 Ф 0.01 Ф 1.54 Ф
Figure D12: Continued
224
07-OR-06 (151-155 cm)
100
80
60
40
20
0 Cumulative Weight Percent Weight Cumulative -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
07-OR-06 (151-155 cm)
80 70 60 50 40 30 Frequency Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.6 1.5 2.0 2.6 3.3 3.9 4.8
mode median mean SD S K 2.0 Ф 2.59 Ф 2.67 Ф 1.22 Ф 0.07 Ф 1.32 Ф
Figure D12: Continued
225
07-OR-07 (79-82.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent -4 -2 0 2 4 6 Phi Size Class
07-OR-07 (79-82.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 6 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.25 2.00 2.21 2.86 3.67 3.91 4.79
mode median mean SD S K 3.0 Ф 2.86 Ф 2.92 Ф 1.01 Ф 0.09 Ф 0.99 Ф
Figure D13: Plots of cumulative weight percent versus grain size along with a histogram depicting the grain size distribution for the vibracore collected from meander bend 2 on the Ottawa River.
226
07-OR-07 (146-149.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent -5 -3 -1 1 3 5 Phi Size Class
07-OR-07 (146-149.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 0.40 1.10 1.25 1.70 2.24 2.60 3.47
Mode median mean SD S K 2.0 Ф 1.70 Ф 1.80 Ф 0.84 Ф 0.18 Ф 1.27 Ф
Figure D13: Continued
227
07-OR-07 (180-183.5 cm)
100
80
60
40
20
0 Cumulative Weight Percent -5 -3 -1 1 3 5 Phi Size Class
07-OR-07 (180-183.5 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size -4.24 1.18 1.70 3.19 3.77 4.00 4.65
mode median mean SD S K 4.0 Ф 3.19 Ф 2.79 Ф 2.05 Ф -0.55 Ф 1.76 Ф
Figure D13: Continued
228
07-OR-07 (219-223 cm)
100
80
60
40 Percent 20 Cumulative Weight Weight Cumulative 0 -4 -2 0 2 4 Phi Size Class
07-OR-07 (219-223 cm)
80 70 60 50 40 30 Frequency 20 10 0 -4 -3 -2 -1 0 1 2 3 4 5 Phi Size Class
Φ % Φ5 Φ16 Φ25 Φ50 Φ75 Φ84 Φ95 Φ Size 1.20 1.78 2.05 2.60 3.30 3.76 4.60
Mode median mean SD S K 3.0 Ф 2.60 Ф 2.71 Ф 1.01 Ф 0.17 Ф 1.11 Ф
Figure D13: Continued