GEOMORPHIC EFFECTS OF THE HOCKING RIVER CHANNELIZATION AT
ATHENS, OHIO, ON THE DOWNSTREAM PLANFORM
A thesis presented to
the faculty of
the College of Arts and Sciences of Ohio University
In partial fulfillment
of the requirements for the degree
Master of Arts
Michael Anthony Gregorio
June 2008 2
GEOMORPHIC EFFECTS OF THE HOCKING RIVER CHANNELIZATION AT
ATHENS, OHIO, ON THE DOWNSTREAM PLANFORM
BY
MICHAEL ANTHONY GREGORIO
has been approved for
the Department of Geography
and the College of Arts and Sciences by
Dorothy Sack
Professor of Geography
Benjamin M. Ogles
Dean, College of Arts and Sciences 3
ABSTRACT
GREGORIO, MICHAEL ANTHONY, M.A., June 2008, Geography
Geomorphic Effects of the Hocking River Channelization at Athens, Ohio, on the
Downstream Planform (105 pp.)
Director of Thesis: Dorothy Sack
Channel planform change was investigated along 24 kilometers of the Hocking
River in Athens County, Ohio, by overlaying aerial photographs spanning 67 years into a
geographic information system (GIS) to observe temporal and spatial stream patterns
before and after the Army Corps of Engineers modified the river to control flooding in
the city of Athens. Previous research has suggested that artificial channel adjustments
alter the fluvial geomorphology in the downstream direction by increasing stream volume
and stream velocities, causing erosion of the channel and lateral migration of a stream.
Channel planform mapping was accomplished through digitizing the fluvial
features of a stream and measuring the rates of change. The changes that were observed
by the GIS-based methodology show statistically significant changes in the Hocking
River channel widths, but little change in lateral migration, except in the asymmetry of
meanders bends. Changes in channel width gradually decrease with distance. This lack of
change in position and downstream decrease in width suggest that the channelization did not have much impact on the channel planform.
Approved: ______
Dorothy Sack
Professor of Geography 4
ACKNOWLEDGMENTS
I wish to thank my advisor, Dr. Dorothy Sack, for her time and motivation throughout my graduate education at Ohio University. Her patience was second to none as many deadlines neared and passed, as well as her ability to understand my train of thought. Her knowledge of geomorphology and personal interest in what I was trying to communicate in my research was of a great resource. Her unconditional support allowed me to complete my geography course requirements and thesis to graduate.
I would also like to thank my committee members, Dr. James Lein and Dr.
Margaret Pearce, for their assistance throughout the year; Michael L. Hughes of the
Institute for Local Government Administration and Regional Development (ILGARD) who provided me with considerable insight with the geotechniques that were applied and the geospatial analysis that was undertaken; and ILGARD and Wayne National Forest for the aerial photography that was essential to mapping the Hocking River planform.
Lastly, I would like to thank those who helped mold my understanding of the geographic and hydrological landscape: Dr. Bryon Middlekauff and Dr. Patrick May of
Plymouth State University, New Hampshire, and the late Dr. Mary Stoertz of Ohio
University. My appreciation also goes out to the Ohio University Department of
Geography for a one-year teaching assistantship that allowed me to educate students the complexity of landforms, topographic maps, and aerial photography, and to ILGARD for a graduate research assistantship in my last year of study.
5
TABLE OF CONTENTS
Page
Abstract ...... 3
Acknowledgments...... 4
List of Tables ...... 7
List of Figures ...... 8
Chapter 1: Introduction ...... 10
Chapter 2: Literature Review ...... 14
Chapter 3: Study Area ...... 21
3.1: Hocking River Fluvial Geomorphology ...... 21
3.2: Hydrological History ...... 24
3.3: Stream Classification ...... 26
Chapter 4: Methods ...... 28
4.1: Aerial Photography ...... 28
4.2: Geographic Information Systems ...... 30
4.2.1: Georectification ...... 31
4.2.2: Channel Measurements ...... 35
4.3: Statistical Analysis ...... 45
Chapter 5: Results ...... 47
5.1: Channel Width ...... 47
5.2: Sinuosity ...... 58
5.3: Asymmetry Index ...... 64 6
5.4: Discharge ...... 68
Chapter 6: Discussion ...... 70
Chapter 7: Conclusion...... 74
References ...... 77
Appendix A: Channel Width Measurements ...... 80
Appendix B: Sinuosity Measurements ...... 92
Appendix C: Asymmetry Index Measurements ...... 93
Appendix D: Asymmetry Index Graphs ...... 98
Appendix E: Discharge Measurements ...... 105
7
LIST OF TABLES Page
Table 1: Air Photo/Topographic Map Coverage of Study Area ...... 29
Table 2: Paired Sample One-tailed T-test (Before and After Channelization) ...... 48
Table 3: Paired Sample One-tailed T-test (Air Photo Year to Air Photo Year) ...... 48
3a: Study Area 1...... 48
3b: Study Area 2 ...... 49
3c: Study Area 3...... 49
8
LIST OF FIGURES Page
Figure 1: Location of the Hocking River in Athens County, Ohio ...... 12
Figure 2: Stream Channel Adjustment Model ...... 20
Figure 3: Hocking River Study Area ...... 22
Figure 4: Historical Migration Zone ...... 38
4a: Study Area 1...... 38
4b: Study Area 2 ...... 39
4a: Study Area 3...... 40
Figure 5: Transects ...... 41
5a: Study Area 1...... 41
5b: Study Area 2 ...... 42
5d: Study Area 3 ...... 43
Figure 6: Asymmetry Index ...... 45
Figure 7: Channel Planform (All Air Photo Years) ...... 52
7a: Study Area 1...... 52
7b: Study Area 2 ...... 53
7c: Study Area 3...... 54
Figure 8: Study Area 1 Channel Width...... 55
8a: Channel Width Measurements ...... 55
8b: Channel Width Before and After Channelization ...... 55
Figure 9: Study Area 2 Channel Width...... 56
9a: Channel Width Measurements ...... 56
9b: Channel Width Before and After Channelization ...... 56
9
Figure 10: Study Area 3 Channel Width...... 57
10a: Channel Width Measurements ...... 57
10b: Channel Width Before and After Channelization ...... 57
Figure 11: Sinuosity ...... 59
11a: Study Area 1...... 59
11b: Study Area 2 ...... 59
11c: Study Area 3...... 60
Figure 12: Channel Centerline (All Air Photo Years) ...... 61
12a: Study Area 1...... 61
12b: Study Area 2 ...... 62
12c: Study Area 3...... 63
Figure 13: Meander Locations ...... 65
13a: Study Area 1...... 65
13b: Study Area 2 ...... 65
13c: Study Area 3...... 66
Figure 14: Meander 4 ...... 66
Figure 15: Meanders 5, 6, and 7 ...... 67
Figure 16: Meander 5 Photograph ...... 67
Figure 17: Discharge ...... 68
17a: Total Discharge ...... 68
17b: Discharge Before Channelization ...... 69
17c: Discharge After Channelization ...... 69
Figure 18: Meander 2 and 3 ...... 72
Figure 19: Meander 5, 6, and 7 ...... 72 10
CHAPTER 1:
INTRODUCTION
Studying the changes that take place in a river channel’s planform has been one
the most researched topics in the field of fluvial geomorphology for more than a century
(e.g., Gilbert, 1880; Davis, 1899; Mackin, 1948; Hickin, 1974; Schumm, 1979; Gurnell
and Downward, 1994; Winterbottom, 2000; Hooke, 2004; Hughes et al., 2005). This is
in part due to the significant changes that occur within a fluvial system on a regular basis
as shifts in discharge and sediment load necessitate geomorphic modifications within a
stream’s planform. As geomorphologist W.M. Davis (1889, p. 183) observed, “no one
regards a river as a ready-made feature on the earth’s surface,” adding that “rivers have come to be by slow processes of natural development, in which every peculiarity of a
river’s course and valley form has its appropriate cause.” Uncovering the natural
influences of change and those induced by human interference in the fluvial system
through time, has become a fundamental part of fluvial geomorphic research. With
recent advances in geospatial technology over the past two decades, measuring the
changes incurred in a channel planform, as well as other physical features of streams, has
been much easier to accomplish, especially with the introduction of air photo imagery
and geographic information systems (GIS).
The stream in question for this research, the Hocking River in the state of Ohio,
had a portion of its natural channel through the city of Athens adjusted in 1971 by the
Army Corps of Engineers (ACOE) to reduce large flooding events that had taken place in
prior years. The result of this engineering project was a modified channel that had been 11
artificially realigned, dredged, and widened to accommodate a higher transport capacity to diminish the probability of overbank flow in the city. The purpose of this thesis
research is to map the channel planform over a number of decades before and after the
ACOE channelization of the Hocking River, downstream from the actual engineering
project, and to investigate the extent of the geomorphic effects imposed by the
channelization on the downstream planform.
The channel planform is the trace of a stream in map view, that is, when looking
straight down from overhead. Over a period of time, rivers naturally change their
planform to accommodate the variable episodes of erosion and deposition caused by
changes in the climate and surrounding landscape (e.g., Leys and Werrity, 1999;
Winterbottom, 2000; Hooke, 2004). Fluvial research has also shown that human activity,
such as urbanization, deforestation, intensive agriculture, and channelization, can affect
the morphology of a stream channel through interference with the floodplain and channel
dynamics (Gregory, 2006). Measuring the change in planform helps researchers to
understand the spatial and temporal patterns of a stream and to examine the influences
that cause change to transpire. A number of indices are used to measure change in a
stream channel, including channel width, sinuosity, lateral migration, meander curvature,
and active locations along the channel, such as areas of aggradation and degradation
(Leopold and Wolman, 1957; Leys and Werrity, 1999).
Many changes have been documented downstream from channelized reaches.
These include incision on the channel bed and channel widening through increased
erosion on the outside banks. Theses changes decline in intensity farther downstream 12 where the effects of the channelization are lessened (Brookes, 1985). Newly constructed channels are typically larger than their natural counterparts and can hold higher discharges. This causes the floodplain storage of water to be reduced and higher flows to be transmitted through the artificial channel and downstream away from populated areas
(Hatton, 1999). This leads to widening and deepening of the streams by incision downstream from the channelized section, or flooding (Emerson, 1971). These erosive responses will, in time, generate changes in the gradient. The adjustments can be viewed as a mode of recovery of the disturbed stream from an unstable one (Simon, 1989).
The research hypothesis of this thesis states that the channelization has influenced channel properties of the Hocking River downstream from Athens, Ohio (Figure 1). The null hypothesis is that no significant changes in the downstream channel width, sinuosity, and meander asymmetry occurred. Using aerial photography of the fluvial landscape and
Figure 1. Location of the Hocking River in Athens County, Ohio
13 topographic maps to supplement the research, it may be possible to interpret variations in the geomorphology as genuine channel change. If the impact of the ACOE channelization on the channel planform can be determined through the geographical analysis, steps can be taken to protect property, roads, and agricultural lands from channel erosion that could be taking place along the Hocking River.
14
CHAPTER 2:
LITERATURE REVIEW
Basic theories of fluvial geomorphology are needed to understand the different factors that affect stream channel morphology. Observations of stream planform behavior were well underway by the late 1800s, with research conducted by Gilbert
(1880) and Davis (1899), with their foci on stream processes and erosional cycles, respectively. However, not until the mid-20th century, with the advent of process geomorphology, did geographers begin to research in earnest the causes behind such transformations in a stream, including the measurements of such changes. Eventually, researchers turned to focus on the external influences that have led to major fluctuations in stream discharge and changes in both the channel planform and hydraulic geometry.
In recent decades, the mapping of stream channels with GIS and other geospatial software packages has shifted the research focus to areas of development and urbanization that are of interest to hydrologists, conservationists, environmental planners, and civil engineers through the creation of data layers to find relationships between the physical and cultural landscape. Emphasis on the role of human impact on channel adjustment has created an ideal research environment for fluvial analysis.
Rivers are dynamic landforms that are subject to changes in channel shape and flow pattern. Hydrological research has found that stream channels correct themselves by balancing discharge and the sediment load (Hooke, 2004). If there is a change in one of these factors from interference in the system, then adjustments will take place within the stream channel to accommodate them (Mackin, 1948; Hooke, 2004). As the shape of 15
a river changes in one location, it can have a profound effect that reverberates downstream. Discharge is the volume of stream flow per unit time at a given cross section of the river, and it can also be expressed as cross-sectional area times velocity. An increase of discharge will cause the velocity of a stream to increase, which improves the transportation power. This allows more sediment particles to be transported, increasing the amount of erosion that can take place from the channel banks and streambed
(Friedkin, 1945; Mackin, 1948; Hickin, 1974; Brookes, 1985). Other variables, such as slope, width, and load, have been investigated with planform change, but Leopold and
Wolman (1957) note that the factor having the greatest power to affect the shape of a stream channel is its discharge.
The concept of stream grade was first described by Gilbert (1880) in his research on planation in the Henry Mountains of Utah. His ideas were expressed through the relationship between load and the transportation capacity of a stream. This idea was later restated as the slope of a graded stream being adjusted to provide the velocity required for transportation of the load supplied from the drainage basin (Mackin, 1948). A graded stream is a system that constantly approaches equilibrium, though it will rarely reach that balance (Leopold and Wolman, 1960). On the path to equilibrium, stream channels are seen as agents of transportation (Mackin, 1948), functioning through the relationships among slope, discharge, and load, and through energy transformations in the stream.
With a change in the “controlling factors,” a displacement will occur (Mackin, 1948, p.
472). In addition, when an external change is presented into the system, the reaction will often occur in the direction that will absorb the effects, most likely in the downstream 16
direction. For example, Schumm and Lichty (1965) explain that if slope increases,
velocity of flow will increase as well. This causes erosion to occur through channel
widening and deepening. They note that this change is temporary and the channel
dimensions are not “permanently affected” (Schumm and Lichty, 1965, p. 117). As channel widening or incision takes place through erosion, velocity then decreases, reducing the bed load and allowing aggradation to occur within the stream, completing a
cycle of balance in the system. Over the long term, the stream will assume a dynamic
equilibrium state where the processes that act on the drainage system are balanced with
the fluvial landforms that are created as a result (Schumm and Lichty, 1965, p. 118).
Geomorphic thresholds are the transitions from one state of equilibrium within a
stream system to another. Geomorphic thresholds represent major alterations in a
geomorphic system that result in changes in the morphology of the landform through
time. When a threshold is reached, adjustments in the stream channel morphology will
transform from one state to another and the cycle of dynamic change will begin again
until another threshold is reached. Schumm (1979) investigated the influence of slope
and sediment loads on channel patterns. He found that when a slope increases slightly,
channel migration occurs due to increased flow velocity, causing shear stress to be
applied on the bed and bank of the stream. Schumm (1979, p. 492) states that a
“variation of the valley flow gradient produces river-pattern changes.” This is considered
an extrinsic control of the stream, and channelization can be an example of stream
channel change that can be independently introduced. Schumm (1979, p. 493) adds that 17
the very “existence of a threshold suggests an inability of a landform to adjust readily to a
new equilibrium condition.”
A change in stream channel morphology also takes place depending on the
magnitude and frequency of flows. Wolman and Miller (1959) describe work done by a
stream through a range of flow. They suggest that erosion is controlled by flows of
moderate magnitude during frequent events, generally on an annual basis. However,
flows with a constant rate of recurrence imply a steady regime of erosion and deposition
of sediment in the stream channel, so modest change in the stream occurs (Wolman and
Miller, 1959, p. 66). Larger magnitude flows, such as floods, change the channel dimensions of a stream through scouring and transporting sediment that is impossible to move under normal conditions (Wolman and Miller, 1959, p. 71). Such large flows typically overtop the channel banks, resisting the sinuous path. Most channel change, however, is accomplished by moderate flows, below or at bankfull stage.
Several authors have explored river bends (Leopold and Wolman, 1957; Stolum,
1996; Hooke, 2007). Sinuous (meandering) patterns develop in a stream because of small perturbations in flow. These disturbances, caused by such things as large rocks, pools, riffles, and large woody debris, direct the flow of a stream into the riverbank. The riverbank then deflects and pushes the flow into the opposite bank of the river, with erosion taking place along both channel sides and the stream depositing these sediments in areas of lower stream flow. Stolum (1996, p. 1710) states that “river meandering needs to be understood in terms of chaotic dynamics and self-organization.” Two opposing processes are at play in the river channel: lateral migration from bank erosion 18 that increases the sinuosity of the river, and cutoffs that act to decrease sinuosity.
Sinuosity is the stream’s inclination to move back and forth across the floodplain in an s- shaped pattern, expressed as the ratio between the length of a stream to its valley length.
The development of numerous meanders from an initially straight stream eventually transforms the channel into a chaotic state, causing cutoffs to occur, and allowing the river to transition back into a steady state. Accelerated local change in the river may lead to the occurrence of many cutoffs, which creates a period of slow change thereafter
(Hickin, 1977; Stolum, 1996). These changes are simply part of the natural evolution of meanders, caused by variations of stream flow, adjustments in the stream channel, climatic variations, and the impacts of urbanization (Hooke, 1994).
Hooke (2007) explored how anthropogenic forces affect meanders, researching how human impacts on a river causes downstream planform changes through sediment inputs. Hooke found little direct association from one meander to another and that the behavior of meanders is controlled by gradient, curvature, and bank resistance. Channel migration is localized as meanders absorb erosion and deposition through the widening and narrowing of a channel, conforming to the bend in the river (Hooke, 2007, p. 294).
In the past few decades, many of the adjustments observed in stream channel morphology are due to human interference within the stream system (Brookes, 1985;
Urban and Rhoads, 2003; Hooke, 2004). Changes in channel planform can reflect human-induced alterations between the balance of discharge and sediment supply. For example, river stabilization measures, such as channelization (the focus of this research), may have significant effects on the channel planform. Stream channels that have been 19
directly modified and engineered will often work to regain their natural morphology
unless the new channel modifications are continually maintained (Brookes, 1985). Many
studies have been conducted on channelized rivers in the Midwest United States and in
the United Kingdom (Brookes, 1987; Leeks et al., 1988; Gurnell and Downward, 1994;
Urban and Rhoads, 2003), where there has been an extensive history of human-induced processes on stream channels.
Channelization projects are undertaken to straighten or realign a stream, dredge a new channel to which the stream is diverted, or offset the impact of flooding by diverting flow downstream (Emerson, 1971; Brookes, 1987; Simon, 1989; Hatton, 1999; Urban and Rhoads, 2003; Hooke, 2004). Brookes (1987) specifically researched 46 channelization works and their influence on the downstream geomorphology. Surveying
different rivers in England and Wales, Brookes (1987) explains that there is a rising
concern over human impacts on stream channel morphology, especially as urbanization
continues to increase and human activities alter the landscape. He notes that
disequilibrium is created in a modified channel and that “any repercussions of a man-
induced change at any given location can be transmitted over a wide area, especially in
the downstream direction” (Brookes, 1987, p. 337). He created a model (Figure 2) to
express the adjustments of channel morphology in response to increased flows.
With an increase in channel capacity, large discharge amounts can be confined within the artificial channel, preventing overbank flow. This, in turn, reduces floodplain storage. In addition to higher stream flows, channel slope increases from the reduction of the channel length, friction decreases, and higher velocities are generated, causing 20 erosion downstream. Higher stream velocities cause incision to occur in the channel as sediment deposition arises along the channel banks, narrowing the channel. However,
Brookes (1987) found that in some of his study streams, channel width actually increased and the depth did not change. The controlling factor in this scenario appears to have been bed armoring of the underlying bedrock that could have restricted bed degradation, which in turn prevented incision in the stream channel. Brookes (1987, p. 337) proposes that the “energy of increased flows was sufficient to exceed a threshold required for erosion” to take place externally in the channel and for change to occur through widening.
Figure 2. Stream Channel Adjustment Model (modified from Brookes, 1987)
21
CHAPTER 3:
STUDY AREA
3.1 HOCKING RIVER FLUVIAL GEOMORPHOLOGY
The study area of this thesis encompasses three separate areas of interest along the
Hocking River, downstream from Athens, Ohio, where the ACOE channelization is located. Each study reach is 8000 meters in length, for a research total of 24 kilometers.
Each separate reach begins at a location of drainage change in the stream system that may influence the discharge within each respective study area. For example (Figure 3), Study
Area 1 (SA1) begins at the termination of the channelization in Athens. Study Area 2
(SA2) begins at the confluence of Willow Creek, approximately 600 meters downstream from SA1. Study Area 3 (SA3) begins at the confluence of Federal Creek, 7.5 kilometers downstream from the end of SA2, with its drainage flowing in from the north.
The Hocking River is both a meandering and wandering stream with a bed load consisting of unconsolidated sand, silt, and fine gravel. The river is approximately 152 kilometers in length from its source in central Ohio to its mouth at the confluence with the Ohio River at the town of Hockingport (Sturgeon, 1958). The city of Athens is located 47 river kilometers upstream from this confluence. Other cities along the river include Nelsonville, Logan, and Lancaster, Ohio. The drainage area of the Hocking
River basin at the Athens USGS gaging station is 2442 km², and total drainage area of the
Hocking River is 3108 km² (Hatton, 1999).
Sturgeon (1958) describes the regional landscape as part of the unglaciated
Allegheny plateau. It consists of sloping hills and narrow ridge tops, rising on average 22
120 meters above sea level and topping out at 275 meters along the ridges. The region
displays extensive drainage networks of a dendritic pattern that is heavily forested. The
underlying bedrock is made up of shale, siltstone, sandstone, limestone, and coal, and is
found approximately 150 cm below the alluvial surface of the floodplain (USDA, 1985).
Figure 3. Hocking River Study Area
The width of the Hocking River valley in the study area measures between 0.3 and 1.12 kilometers. The width of the Hocking River channel rarely exceeds 50 meters.
The stream gradient is 1.06 meters per kilometer over the entire length of the river
(Hatton, 1999). The low gradient allows meanders to form in the floodplain. Each study 23
area also has a distinct floodplain landscape. SA1 consists of high stream terraces along
the immediate channel that flood on rare occasions, SA2 flows through a wider
floodplain, and SA3 is confined by a small river valley with steep valley walls.
The region has a humid continental climate type (Dfa in the Köppen system), which includes cold winters with moderate snowfall, and hot summers. Rainfall is evenly distributed throughout the year, with total annual precipitation on average 980
mm, measured in Athens, Ohio (USDA, 1985). The weather is mostly affected by storm systems that pass through the region when warm, humid air from the south collides with drier, colder air from the north and west.
The floodplain is located between steep valley walls and is comprised of alluvial sands and silts. Floodplain soils are classified as part of the Chagrin-Nolin association, which are deep, nearly level, well drained soils (USDA, 1985). Floodplain information was extracted through the USDA Athens County Soil Survey (1985, pp. 16-17 and 35), the individual types of floodplain soils found in the study area include the following:
(1) Cg--Chagrin silt loam: frequently flooded, deep, well drained, nearly level soil
on the floodplain floor.
(2) Nn--Newark silt loam: frequently flooded, deep, poorly drained, nearly level.
(3) No--Nolin silt loam: frequently flooded, deep, well drained, nearly level.
(4) Cd--Chagrin loam: rarely flooded, nearly level, deep, well drained soil on first
terrace above normal floodplain of streams.
The Chagrin-Nolin association is located along major streams in the Hocking
River drainage basin that are subject to frequent (primary floodplain – Cg, Nn, and No) 24
and rare flooding (on first stream terrace – Cd). The first stream terrace runs along either
side of the present floodplain, most notably in Study Area 1. The terrace averages 0.4
and 0.5 kilometer in width, ranging in slope from 0 to 3% (USDA, 1985). Nolin soils
form on the lowest portions of the floodplain.
3.2 HYDROLOGICAL HISTORY
In historic time, the Hocking River has been prone to flooding. The greatest flood
known to have occurred in Athens was in 1907. The 1960s saw an increase in precipitation over the region that created higher amounts of discharge within the drainage basin. In May of 1968, the second highest flood on record occurred, which was 0.82 meters below the 1907 flood. Severe floods had also occurred several years prior in,
1963 and 1964, with damage totaling more than 2.8 million dollars over the course of the decade (ACOE, 1993). Due to these floods and the damage that had occurred in the
Athens area, the 1965 Flood Control Act was initiated for the city of Athens to reduce flows and flooding. This allowed realignment, enlargement, and straightening of a portion of the Hocking River to take place (ACOE, 1993).
This channelization project was constructed by the Army Corps of Engineers and consisted of enlarging 8 kilometers of the natural channel through the city of Athens.
This shortened the river by 425 meters when meanders were cut off to accommodate the widened artificial channel (Hatton, 1999). The channelized reach extended from White’s
Mill Dam, near the intersection of Highway 682 and 56 in Athens, to 300 meters downstream from the US Route 50 bridge. Downstream from Athens, the channelization suddenly constricted back to its natural stream channel geometry, which is a narrow 25
sinuous path, for the remainder of its length to the Ohio River (ACOE, 1993). The 1968
flood was used as the design flood for the channelization project, for the purpose of
reducing floods (ACOE, 1993).
The ACOE channelization project took three years to construct, from 1969 to
1971. It created a wider channel that had an average width of 61 meters across, which
was twice the width of the original natural channel (ACOE, 1993). The slope was
increased from 0.0003 to 0.0004 as a result of the shortened channel (Hatton, 1999).
However, widening of the channel meant that large flows were more common because
the enlarged channel could contain such flows. Brookes (1985) proposed that when a
channel is realigned, that particular channel reach may regress back to its original slope.
Hatton (1999, p. 12) found this to be the case for the channelized Hocking River, stating
that the channel has been “aggrading to achieve equilibrium,” thus decreasing its slope.
Hatton (1999) noted that without maintenance, the river had virtually returned to its
original capacity. Hatton (1999) found that sediments had been vertically and laterally
accreting along the channel and that a volume of 540,000 cubic meters of sediment had been deposited by the river in the new channel, reducing its conveyance capacity to 33% of the original design and creating a nine-year flood return interval, dramatically less than
its proposed forty to fifty year flood level.
Maintenance of the artificial channel was not considered at the time of
construction, but was later explored when the deposition of sediment was found to be
occurring in the new channel (ACOE, 1993). The channelization project involved
minimal bank stabilization for protecting the channel from erosion and migration (Hatton, 26
1999). This led to periodic maintenance of the channel to dredge the accumulating sediments along the stream bed. Dredging was deemed ineffective as sediment continued to build within the channel over the course of several years (ACOE, 1993).
Sedimentation of the channelized reach eventually created a sinuous path of flow as sediment was deposited and flow maneuvered around areas of aggradation.
3.3 STREAM CLASSIFICATION
Using a classification scheme provided by Nanson and Croke (1991), with the geographic information gathered about the Hocking River from this thesis, the Hocking
River downstream from Athens can be described as a combination of a confined, vertical accretion floodplain (Order A2) and meandering, scrolled floodplain (Order B3b).
Nanson and Croke (1991, p. 460) define a floodplain as the surface next to the channel that is inundated once during a given return period, separated from the stream channel by banks and built of sediment transported by the present flow. The processes that take place in floodplain development are lateral accretion and overbank vertical accretion.
Nanson and Croke (1991, pp. 459-460) further describe an alluvial channel as “adjusting
to its hydraulic geometry, building a surrounding floodplain in the process that creates a
balance between the work done in a stream and the resistance of the channel boundary to
be eroded.” Such resistance includes vegetation along the channel banks, human
interference, and valley-floor configuration.
Under the classification guidelines of Nanson and Croke (1991, pp. 470-471), the
Hocking River in Study Areas 1 and 3 would be classified as Order A2, which is a
confined, vertical accretion floodplain with gravels and abundant sand, as well as silty 27 layers, as determined from the floodplain soils (USDA, 1985). It is prone to floods, and sediment is deposited through overbank vertical accretion. An Order A2 stream channel is usually a single thread, straight or meandering channel. The primary characteristic of this stream type is that channel migration is restricted by valley confinement where the channel bends can become fixed in position by the bedrock and valley terraces.
Overbank vertical accretion results from overbank deposition of sediment during floods, the dominant process along certain low-gradient, single-thread channels where there is insufficient stream power to permit channel migration (Nanson and Croke, 1991). Order
B3b streams would best describe Study Area 2, as having unconfined meandering, and a scrolled floodplain with sands and gravel, as determined through floodplain soils (USDA,
1985). Cut-bank erosion and point-bar accretion resulting in lateral extension of meanders are the dominant channel processes, which are in part due to the wider floodplain (Nanson and Croke, 1991).
28
CHAPTER 4:
METHODOLOGY
For this thesis, the channel banks and centerline of the Hocking River study reaches were mapped to measure channel width, sinuosity, and the asymmetry index of meanders before and after the ACOE channelization. Lateral migration was not measured in this study due to little apparent change, and instead, the focus shifted to individual meanders. These measurements have been described by Howard and
Hemberger (1991):
(1) Channel Width – measured perpendicular to channel banks
(2) Sinuosity – the ratio of stream length to valley length
(3) Asymmetry Index – determined by the wavelength of each meander and the
lengths of the channel centerline above and below the point of maximum
curvature to the inflection point of each bend
Measurement and analysis of the channel indices were completed through the acquisition and georectification of aerial photography and the digitization of stream features in
Geographic Information Systems (GIS). Channel width trends were analyzed statistically to determine if change was significant or not. Sinuosity and meander asymmetry were descriptively analyzed through graphical representation.
4.1 AERIAL PHOTOGRAPHY
Air photos were acquired from local and governmental sources to obtain complete coverage of the study area before and after the channelization. Information gathered 29
from these images allowed for the extraction of fluvial geomorphic data for analysis of
channel change over a period of time. Channel changes were investigated using aerial photography of similar scale with decadal coverage for the following years: 1938/1939,
1950/1951, 1959/1960, 1966, 1984, 1994, and 2005 (Table 1). The 1994 and 2005 aerial
images are digital orthophotoquads (DOQs) generated by the Ohio Geographically
Referenced Information Program (OGRIP). The remaining air photos are from the
United States Department of Agriculture (USDA). The first four air photo sets predate
the channelization (1971), while the latter three postdate the engineering modification.
Table 1. Air Photo/Topographic Map Coverage of Study Area
YEAR FILM/MAP TYPE SCALE SOURCE 1938/1939 B&W 1:20000 USDA 1950/1951 B&W 1:20000 USDA 1959/1960 B&W 1:20000 USDA 1966 B&W 1:20000 USDA 1984 B&W 1:12000 USDA 1985 TOPOGRAPHIC 1:24000 USGS 1994 DOQ 1:24000 OGRIP 2005 DOQ 1:24000 OGRIP
After receiving the necessary images, gaps were found in the photographic
coverage of the study area. This issue arose specifically in the 1984 air photo set
provided by Wayne National Forest. Photo coverage of the river was impossible in areas
where the Hocking River was outside the forest boundaries, with several kilometers of the lower reach of the river not included in the flight path. One gap of importance in 1984 was the section of river located immediately downstream from the artificial channel in
Athens, an area of great significance for the analysis of channel planform change. To fill this absent stretch of the river, a 1985 USGS 7.5-minute topographic map was used, 30 though the digitized river in this topographic map likely has inherent geospatial error that could affect the analysis of channel measurements. These gaps in coverage resulted in the separation of the Hocking River downstream from Athens into three individual areas of interest, as described previously.
4.2 GEOGRAPHIC INFORMATION SYSTEMS
All aerial images were scanned, georeferenced, and superimposed to represent a
67-year period that illustrates changes in the Hocking River channel planform. GIS software has become the choice for geographical mapping in fluvial geomorphology for its many advantages in representing data, in comparison to manual analysis of early professional works. Researchers have stated the advantages of using GIS, following the outline provided by Downward et al. (1994, p. 450):
(a) Digitized boundaries derived directly from source provide geometrically stable
representations which are readily stored, retrieved, and manipulated.
(b) Digital warping aids the correction of planimetric errors from the source and the
registration of the corrected information to a common scale and map projection.
(c) Quantitative analysis of linear and areal displacements can be achieved by the
comparison of individual records or sequence within a GIS.
(d) A variety of map products can be produced and refined until they represent the
patterns of interest in the most effective way.
(e) Digital statistical outputs may be exported directly from the GIS into other
analytical software packages for further analysis.
31
Gurnell et al. (1994) outline additional approaches when mapping channel change
in a GIS in order to provide the best possible data for analysis, such as use of aerial
images with similar scales, having the same individual georectify the aerial images, employing a set of standard ground control points (GCPs), registering the information on a common base, and using a standard definition of channel properties, such as channel
widths and the channel centerline. All years were rectified by the author, except for
DOQs, which were completed through OGRIP, and the 1951 air photo set, which was
georectified by an employee of the Institute for Local Government Administration and
Regional Development (ILGARD) at Ohio University for another project. The methods
used matched the author’s approach.
4.2.1 GEORECTIFICATION
Mapping channel planform change began after all data sources had been acquired and digitally scanned into the GIS to prepare for the georectification process. Each air
photo was scanned at 600 dpi (dots per inch) and saved as a TIFF file. Co-registration of
the images to a common scale and projection was applied, set in metric units with a
Lambert Conformal Conic projection and a North American Datum 1983 State Plane
Ohio South coordinate system. The 1994 DOQ of Athens County, Ohio, was used as the
base layer due to its status as professionally created, and thus, of high accuracy. In
addition, the 1994 DOQ better represented the landscape of earlier studies compared to
the 2005 DOQ. The 2005 DOQ showed an increase in urbanization that may have made
georeferencing more difficult to accomplish. 32
Georeferencing air photos to a common base layer using ground control points
was undertaken to represent each air photo at the same scale. This process was carried
out with the georeference toolbar in ESRI ArcGIS v. 9.2 ArcMap software. Hughes et al.
(2006) note that the number, distribution, and type of ground control points affect the
accuracy of the overall map. Leys and Werrity (1999, p. 108) state that “ground control
points should be widely distributed across the image to provide a stable warp.” Hughes
et al. (2006), however, found that GCPs should actually be concentrated near the feature of interest, rather than across the entire image. This is helpful in areas of varying terrain surrounding a floodplain, as is the case around the Hocking River. GCPs that are placed away from the river may “skew the transformation toward the topographically complex area that is not representative of the river channel” (Hughes et al., 2006, p. 4).
There are two different types of GCPs, those that are hard and others that are considered soft. Hard points consist of angular features, whereas soft points are features with “fuzzy edges” (Hughes et al., 2006, p. 4). Examples of hard ground control points include common features observed on an air photo, such as building corners, lampposts, and the corner of a street intersection. Soft points use nonconventional elements on an air photo, such as property lines between fields where there is a transition between vegetation cover and an empty field intersecting an established road. However, buildings were used as the majority of the GCPs and were preferred because they are apt to be stable throughout the historical record of change. Soft features were helpful in transforming the image in areas of minimal hard points, though these points might 33
increase the level of inaccuracy as these features may shift, disappear, or be altered
completely from survey to survey (Hughes et al., 2006).
Some problems were encountered in the georeferencing of ground control points.
The primary concern was the drastically altered landscape between 1938 and 1994.
During this fifty-six year period, many areas that were cropland had fully reforested,
encroaching onto properties that had been abandoned and obscuring structures and roads
from an aerial view. Prime candidates for a GCP on the 1938 air photo were difficult to
view on the 1994 digital orthophoto base layer, as many of these structures were no
longer visible. The same is true for newer structures that could not be located on the
photo of previous decades. This particular problem especially arose around the channelization in Athens, where urbanization had occurred in recent years.
Several authors (e.g., Gurnell, 1994; Winterbottom, 2000; Hughes et al., 2006)
have considered the role of ground control points in preserving a high positional accuracy
of the air photos being utilized in their research. Hughes et al. (2006) found in their study
that at least eight GCPs were needed to provide a level of geospatial accuracy. They found that the error remained relatively the same on average when the number of GCPs
was increased beyond eight, although it improved slightly with an increasing amount.
Many authors have mapped channel change without taking locational error into account
(e.g., Gurnell et al., 1994; Winterbottom, 2000). However, new advances in
geotechnology have recently been used to test control points independently (Hughes et al., 2006). Oftentimes, previous researchers proceeded with channel measurements knowing the likelihood that georectification error was affecting their overall 34 measurement. The root-mean-square-error (RMSE) is used in ArcMap to assign a value of the geospatial accuracy. Each point deviates from its correct position as an image is warped onto the base layer. The difference in location between a GCP on the transformed layer and base layer is represented by the RMSE. Hughes et al. (2006, pp.
12-14) explains that the RMSE is useful in “reconstructing channel change with aerial photographs” and that it “may be an acceptable proxy for average error, though it is a poor indicator of georectification accuracy across entire photo.”
Other limitations in mapping have arisen, such as the spatial resolution of an air photo not allowing identification of subtle features of the stream (Gurnell, 1997). Also, slices of time captured on the air photo sets may miss intervening changes in the channel position between survey periods. Channel adjustments might reverse direction during the time between air photo years and unstable segments could become stable. It is noted by
Gurnell (1997) that any channel change measured should be treated as a minimal estimate. To limit this effect, authors have used decadal coverage when researching stream channel morphology, which is a long enough time period to calculate change, but not too short for channel change to be in effect (Gurnell et al., 1998).
When overlaying all the scanned and georectified air photo sets on top of one another, the position of each digitized stream feature is important in determining fluvial change. Due to the scarcity of ground control points in the Hocking River study area, between 8 and 15 GCPs per air photo were used in the georeferencing to georectify each air photo. These include some soft ground control points, such as a solitary tree that can be distinguishable on each air photo year, as well as field lines. 35
After georeferencing each air photo with ground control points, a second order
polynomial transformation was used to correct displacement in the image caused by relief
and the camera’s perspective. This curvilinear function is popular for aerial photos with
varied terrain that is typical of terrace-floodplain environments in a confined valley.
Transformation of an air photo is never perfect, however; there will always be some
geospatial error within the image. An RMSE value of 10 (meters) or less was used.
4.2.2 CHANNEL MEASUREMENTS
Channel width, sinuosity, and the asymmetry index of meanders were measured from the channel positions digitized from the aerial photography and topographic maps.
Changes seen in the overlay of different survey years can be quantified through planimetric analysis to measure the rate of change. Investigating the possible geomorphic effects of the channelization is only significant if the amount of planform adjustment exceeds the geospatial errors inherent in the map sources (Downward et al., 1994). The accuracy with which planform change can be identified depends upon the map scale, the principles used for identifying the position of river banks, and the accuracy with which that position is surveyed and plotted.
Measuring channel width was accomplished using stationary transects along the
Hocking River. Gurnell and Downward (1994, p. 194) found that at fixed points, “spatial and temporal changes can be observed without the introduction of bias in the study.” The majority of papers on fluvial research use cross-valley transects of the floodplain, however, this thesis took a different approach to creating transects. For this thesis, the
Athens County USDA Soil Survey Map (1985) was imported into the GIS and floodplain 36
soil attributes were extracted to build a floodplain graphically, represented by soil type polygons overlain on the base layer DOQ. The confined Hocking River valley and the first stream terrace, however, resulted in a floodplain configuration that caused cross- valley transects to traverse each other in some locations, making it difficult to separate individual transects from one another.
Instead of using cross-valley transects, the historical migration zone (HMZ), described by Rapp and Abbe (2003, p. 17) as the “area the channel has occupied over the course of the historical record and is delineated by the outermost extent of the channel locations plotted over that time,” was used for the placement of transects along the river
(Figure 4). Transects were located 100 meters apart along each study area (Figure 5).
All channel width measurements and length measurements for sinuosity were made with the measure analysis tool provided in the ArcMap software. Each measurement of channel width, stream and valley length, and meander wavelength was completed three separate times and averaged to accommodate any bias from subtle measuring mistakes, and rounded to the nearest whole number; decimal points are erroneous in the data analysis when geospatial error of upwards of 10 meters was present in some air photos.
Channel width was measured along each transect on each air photo planform
(Appendix A). It is noted by Gurnell (1997) that when measuring channel width, overhanging vegetation will obstruct certain stretches of the channel bank.
Indistinguishable areas of the channel were measured in a systematic way to provide consistency, by assuming the location of the channel bank based on the arrangement of vegetation. In some aerial photographs, a dark line representing the channel bank was 37 perceived beneath the vegetation canopy and used as the channel margin. Winterbottom
(2000) adds that the unvegetated channel, rather than the wetted channel, should be used to define the channel banks. The unvegetated channel represents recent bed disturbances that are independent from the flow regime of the time of the air photo. Winterbottom
(2000, p. 199) specifically defines the channel boundary as that which “encompasses the below water level channel as well as areas of unvegetated or sparsely vegetated gravel.”
By doing this, it eliminates any inconsistencies in the channel measurements from different air photo years, resulting from different seasonal and climatic water levels. 38
39
40
41
42
43
44
Channel width change was investigated along 238 individual historical migration
zone transects, 76 for SA1 and 81 for both SA2 and SA3. The transects were created
perpendicular to the channel banks to identify channel shift and direction between the
survey dates. The locations of channel transects were established on the 1994 DOQ.
Where transects ran diagonally across a channel, the channel midpoint was found and the
channel width was measured perpendicular to the channel banks through that midpoint.
Boundary changes of less than 10 meters that were measured using the map data over the
course of the study period were not considered significant due to errors in the positional
accuracy, rather than resulting from a component of channel movement.
Sinuosity (ratio of stream length to valley length) was measured and determined
from the digitized channel centerline for each air photo year and the river valley
centerline of each of the three study areas (Appendix B). To reduce measurement error by
the author, the centerlines of both the channel and valley were measured in 1000 meter
intervals and added to attain a total length value. It was found that mistakes increased
with increasing length due to computer mouse fatigue.
The asymmetry (As) index of each meander was established by measuring the wavelength (λh) of each individual meander in the Hocking River and the lengths of the
half meanders above (λu) and below (λd) the maximum point of curvature ( |ξ|h [max] ) to
its inflection points (Appendix C). Asymmetry index values range from -1 to 1. Negative
values represent a meander that is moving upstream, and a positive value is movement
downstream. Any change represents a meander shift (Figure 6). 45
Figure 6. Asymmetry Index (modified Engelman, 1996)
Mean annual discharge records were collected from the USGS stream gaging station (03159500) in Athens, Ohio (Appendix E). Measurements exist for the study area over the entire timescale, from 1928 (10 years prior to first air photo survey) through
2005. The years 1997-1999 contain no measured data. Discharge records indicate potential runoff for the study reach, representing cycles of wet and dry periods of rainfall.
The variation in discharge measured before and after channelization can provide an additional explanation of channel planform change as described in the literature review.
4.3 STATISTICAL ANALYSIS
Measurements of channel width, sinuosity, and the asymmetry index represent the variability of channel change in the Hocking River. Channel width measurements were entered and variables calculated in Microsoft Excel. Temporal and spatial averages of all 46 variables were calculated and graphically represented. Descriptive analyses through the graphs were applied for both sinuosity and meander asymmetry. Channel width values, measured along the same transects, but for different years, were compared using one- tailed T-tests, to determine if channel widths for one air photo year are significantly larger from those for the next air photo year. In a similar way, channel widths over the four air photo years prior to channelization were averaged and compared statistically using the one-tailed T-tests with average channel widths of the three air photo years after channelization. A 99% confidence interval for the mean was used as the threshold for significance: p ≤ 0.01. A 95% confidence level was not used because change is expected to occur from air photo year to air photo year in most cases. A value lower than 0.01 is truly significant and the null hypothesis can be rejected:
(1) Null Hypothesis (H0: μ1 = μ2): There is no significant difference between
the values of the two samples of channel widths.
(2) Research Hypothesis (H1: μ1 > μ2): The values of one sample of channel
width are significantly larger than the values of the other sample.
47
CHAPTER 5:
RESULTS
Channel width, sinuosity, and meander asymmetry were measured to observe channel change of the downstream planform of the Hocking River. Qualitative and quantitative assessment of the planform maps suggest that the Hocking River had undergone change in channel width, but little change between 1938 and 2005 in channel position. The measurements and statistical analyses, however, show some important exceptions. Much of the channel position has remained remarkably stable, despite deviating in succeeding surveys in the reaches with meanders (Figure 7).
5.1 CHANNEL WIDTH
The major variable that appears altered after channelization is channel width, which increased in all study areas, especially in the stretch immediately downstream from the ACOE project (Study Area 1). Leopold and Wolman (1957) describe channel width as the single most important factor in channel change, as it is primarily adjusted to changes in discharge. Statistical analyses confirm that the groups of average channel widths by transect for the three air photo years after channelization are significantly larger than those before channelization for each study area (Table 2). Comparisons were also made from air photo year to air photo year for each study area to determine if change was a regular occurrence in the Hocking River channel width decade to decade (Table 3).
The statistical results and graphs (Table 3, Figure 8, 9, and 10) indicate that changes in 48 the channel width over the three study areas were variable before channelization, increased immediately afterwards, then ceased, and in some cases, began to decrease.
Table 2. Paired Sample One-tailed T-test Results Mean Channel Width Before and After Channelization by Study Area
SAMPLES SAMPLE SIZE VALUE (meters) SIGNIFICANCE Study Area 1 Mean Channel Width Before 76 36 p < 0.01 Mean Channel Width After 76 47 Study Area 2 Mean Channel Width Before 81 41 p < 0.01 Mean Channel Width After 81 49 Study Area 3 Mean Channel Width Before 81 37 p < 0.01 Mean Channel Width After 81 47
Table 3a. Study Area 1 Paired Sample One-tailed T-test Results Mean Channel Width Comparisons of Successive Sample Years
SAMPLES SAMPLE SIZE VALUE (meters) SIGNIFICANCE Study Area 1 Mean Channel Width 1938/1939 76 36 p < 0.01 Mean Channel Width 1950/1951 76 40 Mean Channel Width 1950/1951 76 40 p < 0.01 Mean Channel Width 1959/1960 76 35 Mean Channel Width 1959/1960 76 35 p > 0.01 Mean Channel Width 1966 76 35 Mean Channel Width 1966 76 35 p < 0.01 Mean Channel Width 1984/1985 76 44 Mean Channel Width 1984/1985 76 44 p < 0.01 Mean Channel Width 1994 76 50 Mean Channel Width 1994 76 50 p > 0.01 Mean Channel Width 2005 76 48
(T-tests continue on next page)
49
Table 3b. Study Area 2 Paired Sample One-tailed T-test Results Mean Channel Width Comparisons of Successive Sample Years
SAMPLES SAMPLE SIZE VALUE (meters) SIGNIFICANCE Study Area 2 Mean Channel Width 1938/1939 81 45 p < 0.01 Mean Channel Width 1950/1951 81 43 Mean Channel Width 1950/1951 81 43 p < 0.01 Mean Channel Width 1959/1960 81 37 Mean Channel Width 1959/1960 81 37 p > 0.01 Mean Channel Width 1966 81 39 Mean Channel Width 1966 81 39 p < 0.01 Mean Channel Width 1984 81 47 Mean Channel Width 1984 81 47 p < 0.01 Mean Channel Width 1994 81 52 Mean Channel Width 1994 81 52 p < 0.01 Mean Channel Width 2005 81 48
Table 3c. Study Area 3 Paired Sample One-tailed T-test Results Mean Channel Width Comparisons of Successive Sample Years
SAMPLES SAMPLE SIZE VALUE (meters) SIGNIFICANCE Study Area 3 Mean Channel Width 1938/1939 81 39 p < 0.01 Mean Channel Width 1950/1951 81 37 Mean Channel Width 1950/1951 81 37 p > 0.01 Mean Channel Width 1959/1960 81 36 Mean Channel Width 1959/1960 81 36 p < 0.01 Mean Channel Width 1966 81 38 Mean Channel Width 1966 81 38 p < 0.01 Mean Channel Width 1984 81 46 Mean Channel Width 1984 81 46 p > 0.01 Mean Channel Width 1994 81 46 Mean Channel Width 1994 81 46 p > 0.01 Mean Channel Width 2005 81 48
Spatial trends show that in Study Area 1, channel width increased dramatically after channelization within the first 3000 meters downstream of the channelized reach. A plot of downstream trends in channel width for each year in SA1 (Figure 8a) illustrates that a large increase occurred in the first 3000 meters in the 1984/1985, 1994, and 2005 50
study years compared with the air photo years before the artificial channel construction.
Channel width on average in this section of the Hocking River increased 22 meters at a
rate of 0.8 meters per year from 1966 to 1994; channel widths measured in 2005 are
statistically smaller than the channel widths measured in 1994. Average channel width of
the first 3000 meters before channelization remained stable. The average differences in
channel widths farther downstream in SA1 are smaller than the first 3000 meters, but are
still larger on average after channelization. Overall channel widths in SA1 increased by
11 meters, at a rate of 0.4 meters per year after channelization through 1994, before decreasing in size again. Average channel width was relatively stable before
channelization, fluctuating between 36 and 40 meters (Appendix A). Comparing the
average before and after channelization, trends show that channel widths were
statistically larger after channelization as a whole (Table 2 and Figure 8b).
Study Area 2 lies 600 meters downstream from the Study Area 1 reach. Like
SA1, the data (Table 3 and Figure 9a and 9b) show an increase over the entire study area
in channel width after channelization, a rate of 0.4 meters per year through 1994,
increasing from 39 to 52 meters, before decreasing again by 2005 (Appendix A). Before
channelization, channel width decreased from 45 to 39 meters from the beginning of the
study period to 1966, a rate of -0.2 meters per year.
Study Area 3 lies at a considerable distance from the previous two surveys, 7.5
kilometers from SA2. This is due to the stretch downstream of SA2 that was omitted
from the study because of large geospatial errors from a lack of sufficient ground control
points. Study Area 3 experienced a statistically significant increase in channel width 51 after channelization (Table 3 and Figure 10a and 10b). However, the channel width stabilized relatively quickly with little change occurring thereafter. Between 1966 and
2005, average channel width increased 10 meters at a rate of 0.3 meters per year.
However, much of the increase occurred immediately after the channelization (Appendix
A). Between 1984 and 2005, channel width on average remained stable. Channel width measurements in 2005 were actually slightly larger than in the previous surveys. The increase in width after channelization was much smaller compared to the other two study areas. Federal Creek, the largest tributary of the Hocking River in Athens County, flows into the Hocking River at the first transect of SA3. The distance from the ACOE channelization in Athens and the drainage basin influence of Federal Creek may have helped the channel dimensions remain more stable. 52
53
54
55
Figure 8a. Study Area 1 Channel Widths by Transect for each Air Photo Year
Figure 8b. Study Area 1 Mean Channel Width Before & After Channelization 56
Figure 9a. Study Area 2 Channel Widths by Transect for each Air Photo Year
Figure 9b. Study Area 2 Mean Channel Width Before & After Channelization 57
Figure 10a. Study Area 3 Channel Widths by Transect for each Air Photo Year
Figure 10b. Study Area 3 Mean Channel Width Before & After Channelization 58
5.2 SINUOSITY
From one study year to the next, sinuosity measurements in Study Area 1 indicate an increasing trend as the stream lengthens with increasing meander growth, which was continuous well before the channelization (Figure 11a). However, the last measurement in 2005 points to a slight decrease due to a meander cut-off that occurred in the SA1 reach (Meander 4), causing the sinuosity to decrease suddenly as the stream decreases in length (Appendix B). Overall sinuosity remained between 1.1 and 1.2, an indication of little change in the sinuosity in the Hocking River.
Over the study period in Study Area 2, a small increase in sinuosity is observed at a rate that is similar to both the rates of increase before and after channelization (Figure
11b). This can be attributed to the meander train that is located in the study area as the meanders laterally extend over the 67 year time period. Likewise, overall sinuosity remained, as in SA1, around 1.2.
The sinuosity of Study Area 3 remained stable over the study period, at a value of just below 1.1 (Figure 11c). It is within this study reach where the valley is only 0.2 kilometers wide, confining the Hocking River and virtually prohibiting any lateral movement of the stream channel over the timeline of the study, and barring the growth of meanders. Channel centerlines were mapped to represent the Hocking River sinuosity within each study area (Figure 12). 59
Figure 11a. Study Area 1 Sinuosity Change Over Time
Figure 11b. Study Area 2 Sinuosity Change Over Time 60
Figure 11c. Study Area 3 Sinuosity Change Over Time
61
62
63
64
5.3 ASYMMETRY INDEX
The decision to exclude lateral migration as one of the variables analyzed in this thesis was made when the channel planform was digitized on the most recent set of air photos, revealing that the Hocking River had remained essentially in the same sinuous course over the 67 year study period. Focus was shifted to the river’s 18 meanders scattered among the three study areas, the only areas of channel migration (Appendix C and Figure 13). Meanders in this thesis are described as bends that are not controlled by the valley walls and are free moving in the floodplain. All other subtle lateral movements in the study were below the geospatial error and could not be counted as genuine channel change. Meanders were measured using the asymmetry index to denote channel change.
The asymmetry index indicates whether there is a progression downstream or upstream of the maximum point of the meander bend or if a meander is stable.
While some meanders experienced a change in asymmetry after channelization, the majority of the river meanders did not (Appendix D). The greatest changes in asymmetry were observed in the meanders of Study Area 1 and the first three meanders of Study Area 2. Meander 4 in SA1 was cut off sometime between 1984 and 1994, and was completely plugged and rerouted by 2005 (Figure 14). Meander 5 in SA2 experienced lateral extension that took place along the cut bank. This caused Meanders 6 and 7 to translate downstream (Figure 15 and 16). The rest of the meander train in SA2, meanders 8 through 16, remained relatively fixed with only subtle changes in position. In
SA2, a wider valley permitted greater movement of the stream channel and meanders formed as the stream shifted in its own alluvium. 65
Figure 13a. Study Area 1 Meanders
Figure 13b. Study Area 2 Meanders 66
Figure 13c. Study Area 3 Meanders
Figure 14. River Position over Study Period at Meander 4 67
Figure 15. River Position over Study Period at Meanders 5, 6, and 7
Figure 16. Ground View of Meander 5 68
5.4 DISCHARGE
Overall trends show an increase in the amount of discharge flowing through the
Athens stream gage (USGS No. 03159500), located within the channelized reach, over the 67-year time period (Figure 17a). When the time period is split into before (Figure
17b) and after (Figure 17c) the ACOE channelization, discharge was decreasing before
1971 and increasing after 1971. The channelization project allowed greater discharge, resulting in accelerated flow, which may have contributed to downstream channel widening and deepening by erosion through the principles described by Brookes (1987).
Figure 17a. Discharge at Athens Stream Gage (No data 1997 - 1999)
69
Figure 17b. Discharge before channelization at Athens Stream Gage 1928 - 1970
Figure 17c. Discharge after channelization at Athens Stream Gage 1971 – 2005 70
CHAPTER 6:
DISCUSSION
The planimetric trends observed show that channelization of the Hocking River caused statistically significant changes in the downstream planform, particularly channel width. Little change is seen in the sinuosity and the asymmetry of meanders. The increase in width after channelization was greatest near the channelized reach in Study
Area 1, and less in Study Areas 2 and 3. This downstream channel widening indicates that there may be bed armoring along the stream bed since several authors have described incision rather than widening of the channel to occur through the effects of channelization. The Hocking River could very well be close to bedrock since it lies about
150 cm beneath the Hocking River floodplain alluvium (USDA 1985).
The geomorphic effects of the channelization on the downstream planform are caused by two open channel hydraulic principles. Analysis of the channel width measurements illustrate that the Hocking River channel increased in width after channelization, with relative stability before construction. It has been revealed by other researchers (Brookes, 1987; Urban and Rhoads, 2003; Hooke, 2004) that after channelization, the channel capacity increases, reducing the floodplain storage. Stream flow is then increased from the enhancement of the channel slope and from a decrease in friction, causing higher velocities to be generated and erosion to occur downstream. As channel width increases, other stream variables, such as velocity and slope, are decreased, causing a negative feedback to take place over time, slowing the erosive processes as the stream is graded. A decrease in channel width eventually occurred by 2005, though 71 width was still larger on average in 2005 than before channelization. Hatton (1999) found that the artificial channel had vertically and laterally accreted, reducing its storage capacity to 33% of the design capacity. This sedimentation has allowed a more natural, sinuous path within the channelized reach to form, decreasing the overall width of the channelization at normal flow.
The Venturi effect also takes place downstream from the channelization as accelerated flows move through the constriction of the stream between the widened artificial channel and the narrower natural channel. Pressure from the increased discharge is exerted on the channel dimensions as the natural stream tries to contain the larger discharge through the conservation of mass, resulting in erosion on the channel banks.
This influence is weakened farther downstream as flows are absorbed into the fluvial landscape. This process may have taken place with the spatial decrease in channel width downstream. In addition, with the increase in sedimentation in the channelized reach, the wider channel has slowly decreased in size, reducing this effect over time.
Because SA2 and SA3 show lessened rates of increasing channel width compared to SA1, and no upstream to downstream trends after channelization, changes in the channel widths in Study Areas 2 and 3 may reflect a more natural increase rather than one caused by channelization. SA2 and SA3 include influences from several other streams coming into the system, and vegetation providing stability to the channel banks.
It can be assumed that the changes in sinuosity are reflected in the meanders alone as visual assessment observed little lateral migration occurring in the Hocking River.
With no large shifts in sinuosity, this lack of change can be attributed to the confined 72
valley that has allowed little movement of the stream through the floodplain. Changes in
the sinuosity are subtle, except in the area where the cut-off took place in Study Area 1.
In addition, woodland vegetation lines the channel banks for much of the course of the
Hocking River. Vegetation supplies stability to the stream channel, resisting movement
in the channel planform (Hupp and Osterkamp, 1997). Interestingly, changes in sinuosity were found to be focused in the meanders, specifically located where there is an absence
of vegetation along the channel banks, thus allowing erosion to take place due to bank
instability (Figure 18 and 19).
Fig. 18. Aerial View Meander 2/3 Fig. 19. Aerial View of Meanders 5/6/7 (Google Earth, 2008) (Google Earth, 2008)
Changes in the asymmetry of meanders cannot be attributed to the channelization.
As observed, some meanders had changed from an upstream position to a downstream
position, while others had no discernible change or pattern in their form. These progressions can be normal channel movement. Hooke (1997) explains that meanders absorb geomorphic changes that are introduced into the system. In most of the Hocking 73
River meanders presented, the asymmetry index showed little change from one direction
to another (Appendix D). Lateral extension of meanders and translation downstream was the primary adjustment that occurred in the Hocking River.
74
CHAPTER 7:
CONCLUSION
In conclusion, the channelization has indeed induced some change in downstream planform attributes of the Hocking River. Channelization has been shown to influence the geomorphology of a stream downstream from human constructs and affect property and agriculture. Very little change can be credited to lateral migration, which is why this research focused on channel width, sinuosity, and the asymmetry of meanders. The geomorphic effects can be dramatically seen in an enhancement of channel width immediately downstream from Athens in the years following the construction of the
ACOE artificial channel. However, the channelization’s influence is diminished over time and distance as sediment is deposited in the artificial channel, reducing its capacity to transport sediments and large flows, and with distance from the channelization.
All three study areas have higher channel width values after channelization, but the most significant is observed in Study Area 1, illustrating a decreasing influence with increasing distance downstream from Athens. Other influences on the channel properties within the system may include discharge from tributaries entering the study reaches, as well as impacts of land use through urbanization, forest and intensive agricultural practices, and strip-mining, though the latter has been greatly diminished in scope in recent times (Engelman, 1996; Gregory, 2006).
An increase in urbanization adjacent to the river was observed on the aerial photography, especially near the channelized reach in Athens. The resulting increase in impermeable surfaces prohibits infiltration from rainfall and encourages surface runoff. 75
This would increase the already high discharge flowing through the artificial channel.
However, this influence would decrease with distance away from Athens and the ACOE
channelization. Urbanization downstream is minimal and any impact would be negligible,
with the exception of local geomorphic changes in the stream caused by bridge construction and barriers.
The small amount of change in channel position is probably the result of valley
confinement and confinement by the stream terrace above the floodplain, as well as
woodland vegetation providing stability to resist movement of the channel, allowing
width to be the dominant geomorphic effect of the channelization. Areas that do show
movement are in meanders at locations without extensive vegetation. Changes in
meander asymmetries, however, cannot be directly tied to the channelization, and are
probably dictated by the local geomorphology (Hooke, 1997). Additional research on the
Hocking River downstream from the artificial channel is needed to provide insight into
changes of the stream’s channel morphology, specifically the channel geometry, to
validate many of the hypotheses presented in this thesis. However, channel cross
sections would have to have been measured soon after channelization to observe its initial
geomorphic effects.
A study of strip mining along Monday Creek has previously been conducted
upstream from Athens, Ohio (Engelman, 1996). Measuring several channel properties,
the study shows that the increase in bed load supplied by the excavation of the mines
widened the Hocking River after a period of narrowing below its confluence with
Monday Creek. Strip mines dot the rugged landscape of Appalachian Ohio and 76
additional work is needed to determine if observed changes in the Hocking River channel
could be related to the strip mines surrounding the study reaches and the sediment increases that would be a result.
The goal of this thesis is to uncover the influence that channelization has had on the observed downstream planform. Though channel width increased, property has not
been greatly affected due to little migration of the stream channel, both before and after
channelization. Several investigations have found channel change of great extent caused
by human-induced influences, but due to valley confinement and vegetation along the
stream, the Hocking River has remained fairly stable over the past 67 years. Because
trends in the channel width show a decrease in size at present due to sedimentation in the
ACOE channelization, there is no reason to believe any significant alterations of the
stream behavior will occur anytime in the near future, barring normal meander growth
and cut-offs, extensive maintenance of the channelization by the ACOE, and catastrophic
flooding events that will ultimately change the fluvial landscape. The Hocking River
downstream from Athens for the time being is relatively stable with minimal effects
imposed by the ACOE channelization project.
77
REFERENCES
ACOE. (1993). Hocking River sediment study: Athens, OH local protection project. U.S. Army Corps of Engineers, Huntington District: 36p.
Brookes, A. (1985). Downstream morphological consequences of river channelization in England and Wales. The Geographical Journal 151: 57-62.
Brookes, A. (1987). River channel adjustments downstream from channelization works in England and Wales. Earth Surface Processes and Landforms 12: 337-351.
Davis, W.M. (1889). The rivers and valleys of Pennsylvania. National Geographic Magazine 1: 183-253.
Davis, W.M. (1899). The geographical cycle. The Geographical Journal 14: 481-504.
Downward, S.R., A.M. Gurnell, and A. Brookes. (1994). A methodology for quantifying river channel planform change using GIS. Variability in Stream Erosion and Sediment Transport. Proceedings of the Canberra Symposium 224: 449-456
Emerson, J.W. (1971). Channelization: A case study. Science 173: 325-326.
Engelman, L.B. (1996). Geomorphological analysis of the Hocking River using ArcCAD. Ohio University Press. Masters Thesis (MS): 62p.
Friedkin, J.F. (1945). A laboratory study of the meandering of alluvial Rivers. U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi: 40p.
Gilbert, G.K. (1880). Report on the geology of the Henry Mountains. 2 ed. Government Printing Office, Washington DC: 226p.
Gurnell, A.M. (1997). Channel change on the River Dee meanders, 1946- 1992 from the analysis of air photographs. Regulated Rivers: Research & Management 13: 13-26.
Gurnell, A.M., M. Bickerton, P. Angold, D. Bell, I. Morrissey, G.E. Petts, and J. Sadler. (1998). Morphological and ecological change on a meander bend: the role of hydrological processes and the applications of GIS. Hydrological Processes 12: 981-993. 78
Gurnell, A.M. and S.R. Downward. (1994). Channel change on the River Dee meanders, 1876-1992. Regulated Rivers: Research & Management 9: 187-204.
Gregory, K.J. (2006). The human role in changing river channels. Geomorphology 79: 182-191.
Hatton, A. (1999). A post audit of the channelized reach of the Hocking River, Athens, Ohio. Ohio University Press. Masters Thesis (MS): 95p.
Hickin, E.J. (1974). The development of meanders in natural river channels. American Journal of Science 271: 414-442.
Hooke, J.M. (2004). Cutoffs galore!: Occurrences and causes of multiple cutoffs on a meandering river. Geomorphology 61: 225-238.
Hooke, J.M. (2007). Spatial variability, mechanisms and propagation of change in an active meandering river. Geomorphology 84: 277-296.
Howard, A.D. and A.T. Hemberger. (1991). Multivariate characterization of meandering. Geomorphology 4: 161-186.
Hughes, M.L., P. McDowell, and W. Marcus. (2006). Accuracy assessment of georectified aerial photographs: Implications for measuring lateral movement in a GIS. Geomorphology 74: 1-16.
Hupp, C.R. and W.R. Osterkamp. (1996). Riparian vegetation and fluvial geomorphic processes. Geomorphology 14: 277-295.
Leopold, L. and M.G. Wolman. (1957). River channel patterns: Braided, meandering, and straight. U.S. Geological Survey Professional Paper 282-B, 51p.
Leopold, L. and M.G. Wolman. (1960). River meanders. Geological Society of America Bulletin 71: 769-794.
Leys, K.F. and A. Werritty (1999). River channel planform change: Software for historical analysis. Geomorphology 29: 107-120.
Mackin, J.H. (1948). Concept of the graded river. Geological Society of America Bulletin 59: 463-512.
Nanson, G.C. and J.C. Croke. (1991). A genetic classification of floodplains. Geomorphology 4: 459-486. 79
Rapp, C.F. and T.B. Abbe. (2003). A framework for delineating channel migration zones. Washington State Department of Ecology Final Draft Publication: 139p.
Schumm, S.A. and R.W. Lichty. (1965). Time, space, and causality in geomorphology. American Journal of Science 263: 110-119.
Schumm, S.A. (1979). Geomorphic thresholds: The concept and its application. The Institute of British Geographers 4: 485-514.
Simon, A. (1989). A model of channel response on disturbed alluvial channel. Earth Surface Processes and Landforms 14: 11-26.
Stolum, H. (1996). River meandering as a self-organization process. Science 271: 1710-1713.
Sturgeon, M.T. and Associates. (1958). Geology and Mineral Resources of Athens County, Ohio. Ohio Department of Natural Resources, Division of Geological Survey: 600 pp.
Urban, M.A. and B.L. Rhoads. (2003). Catastrophic human-induced change in stream- channel planform and geometry in an agricultural watershed, Illinois, USA. Annals of the Association of American Geographers 93: 783-796.
USGS. (2008). Hydrological data for Hocking River (USGS site 03159500), http://waterdata.usgs.gov/usa/nwis/OH/site_no=03159500
Winterbottom, S. (2000). Medium and short-term channel planform changes on the Rivers Tays and Tummel, Scotland. Geomorphology 34: 195-208.
Wolman, M.G. and J.P. Miller. (1959). Magnitude and frequency of forces in geomorphic processes. Journal of Geology. 68: 54-74.
80
APPENDIX A:
CHANNEL WIDTH MEASUREMENTS
Study Area 1 Channel Widths
METERS
TRANSECT 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 5 44 43 36 33 38 44 51 6 30 37 32 32 35 45 38 7 40 35 34 34 42 49 40 8 37 36 34 33 40 57 40 9 37 37 32 36 43 52 40 10 35 34 30 32 40 54 45 11 26 26 32 30 38 57 46 12 32 35 28 35 44 61 44 13 33 34 35 36 45 66 48 14 33 39 37 38 39 53 51 15 35 38 40 40 37 54 48 16 36 41 37 36 41 57 46 17 33 41 35 43 45 62 48 18 34 37 34 33 41 55 48 19 35 33 30 25 38 51 44 20 36 40 27 34 43 59 53 21 37 49 50 38 50 84 72 22 35 31 38 37 44 58 55 23 46 47 41 41 42 59 65 24 31 37 37 36 44 69 81 25 40 39 44 34 36 53 68 26 35 38 36 39 52 70 67 27 30 31 34 34 46 67 65 28 28 34 31 27 37 44 46 29 28 30 33 34 37 48 52 30 32 46 36 33 43 48 50 31 35 41 34 33 41 54 50 32 39 52 35 34 47 55 45 33 37 42 29 28 42 49 43 34 36 43 29 30 38 45 37 35 31 40 34 29 38 44 42 36 34 45 36 35 40 45 45 37 54 58 32 25 36 44 45 38 43 69 64 30 46 57 50 39 41 30 43 36 47 54 61 40 49 38 39 52 59 52 68 41 40 50 34 36 54 71 82 42 58 50 34 31 35 50 40 81
43 55 60 50 62 67 58 66 44 46 37 26 38 87 49 61 45 40 31 32 31 42 31 33 46 45 40 30 49 55 45 55 47 27 38 29 38 54 50 49 48 30 33 33 41 48 40 45 49 35 39 34 29 49 39 47 50 31 37 32 28 50 42 47 51 36 40 37 31 47 42 47 52 39 41 34 30 44 43 55 53 31 38 38 29 44 41 42 54 38 39 37 32 39 43 48 55 31 43 34 32 43 53 50 56 37 45 48 41 45 59 53 57 31 55 33 36 47 46 41 58 28 37 42 44 44 51 47 59 38 49 34 36 50 61 56 60 35 47 35 28 45 55 56 61 34 56 39 37 40 41 33 62 33 53 32 40 39 49 33 63 49 58 42 44 56 54 72 64 30 35 36 37 41 57 58 65 30 30 25 30 39 28 33 66 29 29 31 34 34 34 40 67 30 32 33 36 35 40 43 68 27 27 34 39 38 39 43 69 30 37 37 38 40 39 43 70 31 35 34 34 47 60 52 71 32 31 38 25 41 35 47 72 36 38 33 31 41 34 36 73 37 41 26 36 54 43 51 74 38 32 34 37 45 45 35 75 36 31 33 30 35 34 34 76 30 31 36 25 37 32 37 77 32 36 30 26 37 32 36 78 34 39 31 36 43 37 48 79 33 37 34 34 39 42 47 80 39 41 34 46 50 44 45
Note: Channel width measurements begin at Transect 5 in Study Area 1
82
Study Area 1 Mean Channel Width per 1000 Meters
METERS WIDTH 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 500-1000 37 37 33 33 40 50 42 2000 33 36 33 35 41 57 47 3000 34 38 38 35 43 60 62 4000 40 46 37 33 43 50 49 5000 41 42 33 38 54 48 52 6000 34 43 37 34 45 49 50 7000 32 39 34 37 41 44 45 8000 35 36 33 32 42 38 42
Study Area 1 Mean Channel Width per Air Photo Year
METERS YEAR 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 WIDTH 36 40 35 35 44 50 48
83
Study Area 2 Channel Widths
METERS
TRANSECT 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 0 33 41 30 33 40 49 48 1 35 34 35 39 41 46 44 2 29 32 26 30 42 37 34 3 31 37 33 33 43 42 44 4 30 38 31 28 42 46 51 5 39 39 30 35 50 50 58 6 39 45 29 37 45 47 55 7 36 41 32 35 43 43 49 8 36 37 37 35 50 46 59 9 37 37 24 34 45 44 46 10 35 35 25 31 44 39 45 11 42 39 27 33 36 42 50 12 56 41 35 37 38 52 51 13 57 44 44 45 44 60 50 14 42 42 34 39 55 47 53 15 51 43 34 39 49 47 56 16 69 80 73 74 58 55 57 17 66 55 42 56 66 98 110 18 43 48 38 52 52 48 54 19 46 41 35 42 51 58 50 20 48 51 47 50 61 66 64 21 60 55 58 50 61 60 62 22 43 46 46 28 47 46 46 23 41 36 39 35 37 47 45 24 43 41 36 35 42 48 37 25 52 46 39 42 44 56 52 26 58 45 38 40 45 56 52 27 76 69 41 30 38 54 43 28 94 73 36 41 33 43 46 29 90 58 48 68 46 58 48 30 41 35 35 39 39 44 43 31 41 37 34 34 41 42 41 32 43 35 35 30 46 41 41 33 46 37 38 39 50 49 43 34 45 36 39 37 47 47 49 35 41 37 37 34 44 48 51 36 46 41 38 38 45 50 54 37 46 37 36 41 48 48 52 38 44 35 38 40 45 50 48 39 40 36 34 39 50 47 46 84
40 39 41 38 37 47 43 43 41 35 34 35 34 42 44 34 42 39 41 38 41 43 46 39 43 41 35 36 36 46 47 42 44 52 44 38 38 58 48 45 45 49 49 38 54 54 53 51 46 38 44 43 48 51 57 52 47 44 41 31 39 54 44 50 48 40 34 37 41 52 63 73 49 40 38 48 39 42 48 83 50 36 42 33 29 50 45 54 51 49 54 36 41 54 48 42 52 69 39 36 34 81 80 50 53 51 50 38 34 48 62 62 54 56 38 34 32 43 40 33 55 58 46 27 39 51 60 48 56 83 81 24 85 55 51 53 57 69 56 28 49 48 47 44 58 72 53 37 33 39 39 52 59 50 37 46 32 35 55 48 60 53 38 38 31 48 52 38 61 44 34 41 30 42 59 51 62 36 41 33 34 37 44 33 63 51 39 40 39 52 53 38 64 35 34 45 33 45 47 53 65 32 39 41 52 59 66 52 66 43 45 39 45 56 65 41 67 47 41 43 37 45 75 37 68 37 34 36 34 44 85 51 69 31 33 39 35 51 38 37 70 26 27 30 30 40 38 30 71 32 41 41 34 38 39 33 72 33 39 42 37 39 48 43 73 33 42 35 34 48 41 26 74 36 46 39 39 37 41 32 75 30 33 30 29 37 39 31 76 34 41 34 32 44 42 37 77 24 47 39 23 48 54 43 78 32 46 30 37 62 68 42 79 44 51 62 52 75 87 53 80 30 27 24 41 37 72 59
85
Study Area 2 Mean Channel Width per 1000 Meters
METERS
WIDTH 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 1000 35 38 30 34 44 44 48 2000 52 48 41 46 51 57 59 3000 60 50 42 41 43 51 47 4000 43 37 37 37 46 47 47 5000 41 40 38 40 49 49 52 6000 61 49 34 41 50 53 47 7000 38 37 39 37 47 57 42 8000 33 41 38 36 46 53 40
Study Area 2 Mean Channel Width per Air Photo Year
METERS YEAR 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 WIDTH 45 43 37 39 47 52 48
86
Study Area 3 Channel Widths
METERS
TRANSECT 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 0 35 35 38 32 50 46 30 1 28 36 33 39 46 53 35 2 32 35 28 34 43 45 52 3 33 34 30 31 37 41 46 4 34 35 32 30 34 41 45 5 33 32 38 31 39 51 49 6 33 38 45 34 52 55 55 7 34 36 32 48 40 40 41 8 69 59 52 58 64 57 60 9 37 47 35 36 45 47 48 10 43 42 37 37 47 47 48 11 35 42 42 36 47 47 49 12 37 34 38 35 40 47 55 13 33 35 34 36 40 41 52 14 43 43 37 41 48 46 48 15 46 27 35 44 46 47 45 16 53 37 38 47 56 40 49 17 37 31 33 35 48 42 48 18 42 35 33 40 48 49 55 19 43 48 37 40 49 45 55 20 36 48 32 36 46 41 42 21 30 34 33 32 45 44 41 22 32 31 31 36 41 44 34 23 37 38 33 36 42 45 39 24 35 36 39 37 43 48 44 25 30 33 32 38 40 51 43 26 33 40 34 35 40 44 42 27 38 42 40 36 51 44 45 28 39 36 30 32 41 40 36 29 39 32 29 30 37 44 37 30 38 31 33 35 47 38 43 31 34 35 32 38 42 45 44 32 28 36 30 35 50 46 49 33 31 32 30 38 47 44 42 34 28 33 30 34 43 43 49 35 31 34 37 39 49 40 48 36 37 37 39 39 53 41 48 37 32 42 38 41 56 48 52 38 37 43 30 44 59 46 55 39 35 41 41 41 49 53 46 87
40 34 37 40 47 54 60 64 41 29 33 40 42 47 46 55 42 33 37 27 39 41 46 45 43 41 36 33 41 50 44 41 44 46 39 33 40 49 41 51 45 45 36 30 34 49 43 46 46 43 34 28 37 50 36 41 47 53 45 28 37 55 39 52 48 50 34 31 35 48 39 56 49 40 34 34 40 47 42 47 50 35 32 37 35 42 42 45 51 41 29 34 32 47 48 47 52 42 30 34 33 46 51 46 53 45 35 41 39 40 55 50 54 45 38 45 41 46 47 52 55 40 36 42 40 40 45 52 56 43 31 39 35 36 45 46 57 45 28 37 37 43 45 45 58 46 34 37 41 47 43 45 59 43 39 38 41 45 46 45 60 41 44 39 44 41 51 42 61 40 40 40 42 39 52 47 62 38 37 39 38 43 53 49 63 40 36 37 43 42 48 47 64 42 40 38 36 42 47 45 65 39 45 42 38 46 57 54 66 39 49 39 40 50 59 62 67 43 46 34 39 46 48 55 68 40 45 36 35 44 51 55 69 50 39 40 37 42 47 52 70 41 25 38 37 42 40 47 71 40 28 41 40 45 47 55 72 41 29 40 36 43 45 55 73 43 32 36 34 44 44 53 74 37 23 31 37 43 45 45 75 47 27 35 38 43 46 44 76 41 32 36 38 51 56 48 77 38 37 41 38 49 56 60 78 39 36 43 42 52 50 50 79 37 42 40 37 46 43 44 80 37 38 40 36 43 45 47
88
Study Area 3 Mean Channel Width per 1000 Meters
METERS WIDTH 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 1000 37 39 36 37 45 48 46 2000 40 38 36 39 47 44 50 3000 35 35 34 35 43 44 40 4000 33 37 35 39 50 46 50 5000 41 36 32 38 48 42 48 6000 43 35 38 38 43 47 47 7000 41 40 38 38 44 50 51 8000 40 32 38 38 46 48 50
Study Area 2 Mean Channel Width per Air Photo Year
METERS YEAR 1938/1939 1950/1951 1959/1960 1966 1984/1985 1994 2005 WIDTH 39 37 36 38 46 46 48
89
Study Area 1 Channel Width Measurements Before and After Channelization
TRANSECT BEFORE AFTER TRANSECT BEFORE AFTER TRANSECT BEFORE AFTER METERS METERS METERS 5 39 44 32 40 49 59 39 55 6 33 39 33 34 45 60 36 52 7 36 44 34 35 40 61 41 38 8 35 46 35 34 41 62 39 40 9 36 45 36 37 43 63 48 61 10 33 46 37 42 42 64 35 52 11 28 47 38 51 51 65 29 33 12 32 50 39 38 54 66 31 36 13 35 53 40 45 60 67 33 39 14 37 48 41 40 69 68 32 40 15 38 47 42 43 42 69 35 41 16 37 48 43 57 64 70 34 53 17 38 52 44 37 66 71 32 41 18 34 48 45 34 35 72 34 37 19 31 44 46 41 52 73 35 49 20 34 51 47 33 51 74 35 42 21 44 69 48 34 44 75 33 34 22 35 52 49 34 45 76 31 35 23 44 55 50 32 46 77 31 35 24 35 65 51 36 45 78 35 43 25 39 52 52 36 48 79 34 43 26 37 63 53 34 43 80 40 47 27 32 59 54 37 43 28 30 42 55 35 49 29 31 45 56 43 52 30 37 47 57 39 45 31 36 48 58 38 47
Note: Channel width measurements begin at Transect 5 in Study Area 1
90
Study Area 2 Channel Width Measurements Before and After Channelization
TRANSECT BEFORE AFTER TRANSECT BEFORE AFTER TRANSECT BEFORE AFTER METERS METERS METERS 0 34 45 29 66 51 58 49 43 1 36 43 30 38 42 59 41 46 2 29 38 31 36 41 60 40 46 3 33 43 32 36 43 61 37 51 4 32 47 33 40 47 62 36 38 5 36 53 34 39 48 63 42 48 6 37 49 35 37 48 64 37 49 7 36 45 36 41 49 65 41 59 8 36 51 37 40 49 66 43 54 9 33 45 38 39 48 67 42 53 10 32 43 39 37 48 68 35 60 11 35 43 40 39 44 69 34 42 12 42 47 41 35 40 70 28 36 13 47 51 42 40 43 71 37 37 14 39 52 43 37 45 72 37 43 15 41 51 44 43 51 73 36 38 16 74 56 45 47 53 74 40 37 17 55 91 46 43 53 75 31 35 19 41 53 48 38 63 77 33 48 20 49 64 49 41 57 78 36 57 21 56 61 50 35 49 79 52 72 22 41 46 51 45 48 80 31 56 23 38 43 52 44 70 24 39 42 53 43 58 25 45 51 54 40 39 26 45 51 55 42 53 27 54 45 56 68 53
91
Study Area 3 Channel Width Measurements Before and After Channelization
TRANSECT BEFORE AFTER TRANSECT BEFORE AFTER TRANSECT BEFORE AFTER METERS METERS METERS 0 35 42 29 32 39 58 39 45 1 34 45 30 34 43 59 40 45 2 32 47 31 35 43 60 42 45 3 32 41 32 32 49 61 40 46 4 33 40 33 33 44 62 38 48 5 34 47 34 31 45 63 39 46 6 37 54 35 35 46 64 39 45 7 38 40 36 38 47 65 41 52 8 60 60 37 38 52 66 42 57 9 39 47 38 38 53 67 40 50 10 39 47 39 39 49 68 39 50 11 39 48 40 39 59 69 41 47 12 36 47 41 36 49 70 35 43 13 34 44 42 34 44 71 37 49 14 41 47 43 38 45 72 37 47 15 38 46 44 40 47 73 36 47 16 44 48 45 36 46 74 32 44 17 34 46 46 35 42 75 37 45 19 42 50 48 38 48 77 39 55 20 38 43 49 37 45 78 40 50 21 32 43 50 35 43 79 39 44 22 33 40 51 34 47 80 38 45 23 36 42 52 35 47 24 37 45 53 40 48 25 33 45 54 42 48 26 36 42 55 40 46 27 39 47 56 37 42 28 34 39 57 37 45
92
APPENDIX B:
SINUOSITY MEASUREMENTS
Study Area 1
AIRPHOTO STREAM VALLEY SINUOSITY YEAR LENGTH LENGTH 1938/1938 8133 7120 1.1422 1950/1951 8238 7120 1.1570 1959/1960 8468 7120 1.1893 1966 8607 7120 1.2088 1984/1985 8648 7120 1.2146 1994 8516 7120 1.1960 2005 7960 7120 1.1179
Study Area 2
AIRPHOTO STREAM VALLEY SINUOSITY YEAR LENGTH LENGTH 1938/1938 8276 7031 1.1772 1950/1951 8370 7031 1.1905 1959/1960 8439 7031 1.2003 1966 8478 7031 1.2058 1984/1985 8615 7031 1.2254 1994 8660 7031 1.2318 2005 8745 7031 1.2438
Study Area 3
AIRPHOTO STREAM VALLEY SINUOSITY YEAR LENGTH LENGTH 1938/1938 8121 7488 1.085 1950/1951 8101 7488 1.082 1959/1960 8131 7488 1.086 1966 8148 7488 1.088 1984/1985 8124 7488 1.085 1994 8151 7488 1.089 2005 8176 7488 1.092
93
APPENDIX C:
ASYMMETRY INDEX MEASUREMENTS
MEANDER 1 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 1543 455 452 0.0019 1950/1951 1489 428 529 -0.0678 1959/1960 1449 437 586 -0.1028 1966 1475 492 682 -0.1288 1984/1985 1364 521 572 -0.0374 1994 1387 561 592 -0.0224 2005 1449 486 621 -0.0932
MEANDER 2 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 1226 640 362 0.2268 1950/1951 1148 812 385 0.3720 1959/1960 1018 1002 420 0.5717 1966 873 1057 312 0.8534 1984/1985 728 1028 344 0.9396 1994 790 1147 382 0.9684 2005 782 1152 389 0.9757
MEANDER 3 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 966 471 602 -0.1356 1950/1951 928 372 513 -0.1519 1959/1960 802 268 552 -0.3541 1966 886 250 587 -0.3804 1984/1985 856 257 619 -0.4229 1994 800 354 577 -0.2788 2005 791 304 455 -0.1909
MEANDER 4 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 1012 950 712 0.2352 1950/1951 874 932 806 0.1442 1959/1960 806 857 876 -0.0236 1966 726 832 895 -0.0868 1984/1985 829 824 1088 -0.3185 1994 808 966 1006 -0.0495 2005 1048 429 371 0.0553 94
MEANDER 5 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 1047 348 298 0.0478 1950/1951 967 349 409 -0.0620 1959/1960 989 361 565 -0.2063 1966 850 477 511 -0.0400 1984/1985 892 513 466 0.0527 1994 872 702 428 0.3142 2005 854 825 410 0.4859
MEANDER 6 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 491 256 243 0.0265 1950/1951 479 237 267 -0.0626 1959/1960 450 272 212 0.1333 1966 410 258 229 0.0707 1984/1985 527 380 282 0.1860 1994 528 370 358 0.0227 2005 557 453 378 0.1346
MEANDER 7 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 996 248 312 -0.0643 1950/1951 862 310 286 0.0278 1959/1960 808 275 255 0.0248 1966 784 226 324 -0.1250 1984/1985 729 365 232 0.1824 1994 714 386 200 0.2605 2005 681 388 196 0.2819
MEANDER 8 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 1205 604 710 -0.0880 1950/1951 1181 601 695 -0.0796 1959/1960 1029 552 558 -0.0058 1966 1041 659 446 0.2046 1984/1985 1072 729 476 0.2360 1994 1174 794 497 0.2530 2005 1267 901 518 0.3023
95
MEANDER 9 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 722 428 320 0.1496 1950/1951 742 181 510 -0.4434 1959/1960 704 275 421 -0.2074 1966 762 445 354 0.1194 1984/1985 779 591 324 0.3427 1994 796 699 297 0.5050 2005 855 722 245 0.5579
MEANDER 10 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 985 492 818 -0.3310 1950/1951 1057 554 862 -0.2914 1959/1960 1045 599 793 -0.1856 1966 1047 721 691 0.0287 1984/1985 1032 808 694 0.1105 1994 972 727 808 -0.0833 2005 937 743 842 -0.1057
MEANDER 11 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 774 666 621 0.0581 1950/1951 612 620 624 -0.0065 1959/1960 663 617 611 0.0090 1966 599 596 541 0.0918 1984/1985 520 595 606 -0.0212 1994 679 730 662 0.1001 2005 696 742 589 0.2198
MEANDER 12 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 638 602 521 0.1270 1950/1951 606 626 561 0.1073 1959/1960 595 635 570 0.1092 1966 588 641 541 0.1701 1984/1985 618 600 567 0.0534 1994 626 614 625 -0.0176 2005 621 620 616 0.0064
96
MEANDER 13 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 417 219 266 -0.1127 1950/1951 428 255 243 0.0280 1959/1960 453 308 226 0.1810 1966 442 329 224 0.2376 1984/1985 641 501 253 0.3869 1994 674 571 232 0.5030 2005 706 585 212 0.5283
MEANDER 14 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 740 401 369 0.0432 1950/1951 595 357 250 0.1798 1959/1960 627 330 302 0.0447 1966 640 335 344 -0.0141 1984/1985 515 289 407 -0.2291 1994 569 347 398 -0.0896 2005 557 345 432 -0.1562
MEANDER 15 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 813 722 828 -0.1304 1950/1951 845 762 796 -0.0402 1959/1960 826 854 736 0.1429 1966 822 781 777 0.0049 1984/1985 819 722 907 -0.2259 1994 658 595 793 -0.3009 2005 652 561 785 -0.3436
MEANDER 16 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 527 472 280 0.3643 1950/1951 586 487 385 0.1741 1959/1960 567 524 278 0.4339 1966 595 540 326 0.3597 1984/1985 607 523 398 0.2059 1994 622 596 369 0.3650 2005 664 601 362 0.3599
97
MEANDER 17 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 498 444 247 0.3956 1950/1951 556 485 270 0.3867 1959/1960 572 507 276 0.4038 1966 597 573 212 0.6047 1984/1985 428 395 254 0.3294 1994 437 482 195 0.6568 2005 461 467 187 0.6074
MEANDER 18 AIRPHOTO λh λu λd Asymmetry YEAR METERS Index 1938/1938 879 754 502 0.2867 1950/1951 1012 761 596 0.1630 1959/1960 1007 745 580 0.1639 1966 945 705 561 0.1524 1984/1985 941 700 581 0.1265 1994 913 698 553 0.1588 2005 911 721 546 0.1921
98
APPENDIX D:
ASYMMETRY INDEX FIGURES
99
100
101
102
103
104
105
APPENDIX E:
DISCHARGE MEASUREMENTS
Hocking River Discharge (Athens, Ohio – USGS 05030204)
YEAR CMS YEAR CMS YEAR CMS YEAR CMS 1928 27.0 1950 39.3 1972 35.2 1994 36.5 1929 32.7 1951 37.9 1973 40.4 1995 25.8 1930 17.8 1952 25.2 1974 36.1 1996 54.8 1931 19.3 1953 13.4 1975 40.9 1997 NO DATA 1932 20.2 1954 8.1 1976 31.2 1998 NO DATA 1933 31.5 1955 21.0 1977 21.3 1999 NO DATA 1934 11.4 1956 29.5 1978 35.3 2000 25.2 1935 33.6 1957 22.3 1979 49.8 2001 22.5 1936 27.3 1958 32.9 1980 44.6 2002 24.2 1937 38.9 1959 25.3 1981 32.5 2003 35.1 1938 35.0 1960 17.0 1982 27.0 2004 51.5 1939 30.7 1961 32.4 1983 31.0 2005 42.1 1940 29.9 1962 24.3 1984 32.1 1941 18.2 1963 23.6 1985 31.5 1942 22.0 1964 25.6 1986 26.7 1943 30.0 1965 22.8 1987 18.4 1944 19.4 1966 31.3 1988 19.0 1945 39.2 1967 25.6 1989 53.5 1946 26.7 1968 35.6 1990 50.7 1947 29.9 1969 19.0 1991 39.9 1948 43.1 1970 20.9 1992 19.5 1949 25.3 1971 26.7 1993 27.2