Introduction to the Physical Geography of Medium-Sized Rivers, Focusing on the Southeastern and South-Central United States (original) (raw)
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The 2006 Binghamton Geomorphology Symposium on The Human Role in Changing Fluvial Systems
Geomorphology, 2006
Historical and modern scientific contexts are provided for the 2006 Binghamton Geomorphology Symposium on the Human Role in Changing Fluvial Systems. The 2006 symposium provides a synthesis of research concerned with human impacts on fluvial systemsincluding hydrologic and geomorphic changes to watershedswhile also commemorating the 50th anniversary of the 1955 Man's Role in Changing the Face of the Earth Symposium [Thomas, Jr., W. L. (Ed.), 1956a. Man's Role in Changing the Face of the Earth. Univ. Chicago Press, Chicago. 1193 pp]. This paper examines the 1955 symposium from the perspective of human impacts on rivers, reviews current inquiry on anthropogenic interactions in fluvial systems, and anticipates future directions in this field.
Channel planform and land cover changes on a mined river floodplain: Amite River, Louisiana, USA
Applied Geography, 1997
The Amite River in southeastern Louisiana, USA, is a disturbed floodplain and channel, where combined gravel and sand extraction has exceeded 10 million tons per year. To examine relationships between mining and channel change along this river, land cover data from a %-km floodplain reach with variable mining intensity were compiled from photographic, map and documentary sources for two different time periods. These data were manipulated using a geographic information system and analysed using nonparametric statistics, producing statistically robust, moderate correlations between the degree of floodplain mining and change in channel position. The approach and results have application in research, planning and management concerning floodplain disturbances and channel instability. Copyright 0 1997 Elsevier Science Ltd Keywords: channel planform change, floodplain land cover, fluvial geomorphology, geographic information systems, gravel and sand mining
Wetlands, 2009
Human alterations along stream channels and within catchments have affected fluvial geomorphic processes worldwide. Typically these alterations reduce the ecosystem services that functioning floodplains provide; in this paper we are concerned with the sediment and associated material trapping service. Similarly, these alterations may negatively impact the natural ecology of floodplains through reductions in suitable habitats, biodiversity, and nutrient cycling. Dams, stream channelization, and levee/canal construction are common human alterations along Coastal Plain fluvial systems. We use three case studies to illustrate these alterations and their impacts on floodplain geomorphic and ecological processes. They include: 1) dams along the lower Roanoke River, North Carolina, 2) stream channelization in west Tennessee, and 3) multiple impacts including canal and artificial levee construction in the central Atchafalaya Basin, Louisiana. Human alterations typically shift affected streams away from natural dynamic equilibrium where net sediment deposition is, approximately, in balance with net erosion. Identification and understanding of critical fluvial parameters (e.g., stream gradient, grain-size, and hydrography) and spatial and temporal sediment deposition/erosion process trajectories should facilitate management efforts to retain and/or regain important ecosystem services.
Geosphere, 2015
More than 25 cm of rainfall from Tropical Storm Lee (TS Lee) over 2 days in September 2011 resulted in catastrophic flooding (U.S. Geological Survey estimated recurrence interval >100 yr) on several Susquehanna River tributaries emanating from the Appalachian Plateau in north-central Pennsylvania (USA). Helicopter photography and field work were used to prepare a detailed geographic information system database of geomorphic response to the flood along ~250 km of Loyalsock, Muncy, Lycoming, and Fishing Creeks. Unlike the response of many streams to previously described Appalachian floods, fluvial response to the TS Lee flood was extensive in these gravel bed streams, characterized by (1) large-scale avulsions and chute development on the insides of meanders, (2) erosion of gravel from channel margins and transport downstream in large pulses, (3) headwater landslides and alluvial fan activation, (4) major floodplain erosion and deposition, and (5) breaching of anthropogenic berms and reconnection of the main channel to prehistoric floodplain anabranches. Geomorphic work, expressed both as bedload sediment transport and landform change (geomorphic effectiveness) was significant: as much as 55,000 m 3 /km of gravel was transported within a single watershed. Landform changes included erosion of chutes (to 500 m long), gravel bars (point bars and mid-channel bars), channel widening (in places >100%), and reoccupation of former multithread channels previously cut off from the mainstem by historic channel straightening, berming, and dredging. Streams in this region appear to be in a phase of disequilibrium largely in response to major shifts in sediment delivery from their watersheds caused by historic logging and a series of floods ~100 yr ago. Widespread clearcutting (A.D. 1850-1920) contributed large volumes of sediment to these streams. Dendrogeomorphic data bracket a period of aggradation of these logging legacy sediments between the 1870s and 1930s, creating a significant low terrace inset into Pleistocene outwash and glacial sediments. Recent floods in 1972, 1996, 2004, and especially TS Lee in 2011 initiated an enhanced phase of disequilibrium as a geomorphic threshold was crossed, resulting in widespread erosion of logging legacy sediments deposited nearly 100 yr ago. The change in sediment load (increased coarse bedload) as a result of widespread bed and bank erosion caused a change in channel pattern from single thread to multithread. Pattern change was facilitated by aggradation of gravel bars above floodplain elevations which promoted avulsion and chute formation. Based on preflood and postflood geomorphic mapping, >6,700,000 m 3 of gravel were mobilized during the flood across 4 watersheds. Mobilization of logging legacy sediment is occurring as pulses of gravel move downstream episodically. This paper demonstrates the important influences of drainage basin morphometry (e.g., ruggedness number) and fluvial history (land use and geomorphic) in understanding current channel dynamics and basin response to heavy precipitation and flooding. The findings presented herein have significant implications for watershed management and planning. Streams in this region are likely to remain in a protracted phase of readjustment for many decades as complex response to historical land-use change continues. In this dis equilib rium phase most significant rainfall events will likely trigger additional re adjustment and channel change.
The human role in changing fluvial systems: Retrospect, inventory and prospect
Geomorphology, 2006
Historical and modern scientific contexts are provided for the 2006 Binghamton Geomorphology Symposium on the Human Role in Changing Fluvial Systems. The 2006 symposium provides a synthesis of research concerned with human impacts on fluvial systemsincluding hydrologic and geomorphic changes to watershedswhile also commemorating the 50th anniversary of the 1955 Man's Role in Changing the Face of the Earth Symposium [Thomas, Jr., W. L. (Ed.), 1956a. Man's Role in Changing the Face of the Earth. Univ. Chicago Press, Chicago. 1193 pp]. This paper examines the 1955 symposium from the perspective of human impacts on rivers, reviews current inquiry on anthropogenic interactions in fluvial systems, and anticipates future directions in this field.
Floodplain and instream mining are activities that generally increase channel change or instability. To quantify this effect, it is necessary to have some idea of natural or baseline rates of change in rivers in the same region where stream have similar topography, climate, geologic units and vegetation. The Pascagoula River and its tributaries traverse a number of geologic units and the basin shows a diverse set of land cover and land uses, including two streams with considerable historical and recent mining activity. This study quantifies the rates of change in the Pascagoula and some of its tributaries, suggesting at which point planform changes are clearly modified, directly or indirectly, more so by human action. This is done by digitizing the larger and mined tributaries of this system in a GIS using varied sources of data (aerial photographs, topographic maps and digital ortho quarter quadrangles). Polygon areas derived from overlays characterizing changes (areas of erosion, deposition, no change, and areas between channels) in channel position and planform were extracted from the GIS and normalized for scale, so that larger rivers could be compared with the headwaters, as well as smaller rivers and creeks. This study provides insights into the natural factors and anthropogenic activities that influence channel changes in this basin, and thus where future change might be expected to occur. Those insights, in turn, can be applied to management and engineering in the basin.
Excerpts by L. Allan James GEOMORPHOLOGY OF THE LOWER AMERICAN
Geomorphology of the lower American River is relevant to flood hazard management through three issues: (1) stability of channel banks and levees, (2) possible on-going channel enlargement and increases in conveyance, and (3) sediment deliveries to weirs and the lower river. This section addresses the first two concerns by examining geomorphic stability of the lower American River, and presenting evidence of channel erosion from U.S. Geological Survey stream-flow measurements at the Fair Oaks gage.
Tunnelling and Underground Space Technology, 2004
Fluvial geomorphology and historical geomorphology studies were conducted on three sub-basins in the Napa River basin. Despite proximity of the sub-basins, differing physical and climatic settings, land-use histories, and channel modifications have resulted in substantially different sediment sourcing, storage, and transport to the Napa River. We present three examples in which the partnering of field-based fluvial geomorphic data and archival data has fostered a greater understanding of the observed channel morphology and fluvial processes, and how the channel has responded to anthropogenic modifications. Comparatively, sediment sourcing and transport to the Napa River is greatest in Sulphur Creek, followed by Carneros and Soda Creeks, respectively.
2018
Changes in the amount of water and sediment that enter a river can change its shape and size. The way that rivers change is affected by a variety of factors, including the size of the sediment in the river, and past changes to the river. The Diamond Fork River in central Utah has been altered by water deliveredfromthe Colorado River system for over a century. Beginning in 1915, water used for irrigation was delivered through a tributary, Sixth Water Creek, with daily summer flows that were much larger than natural flows. This caused drastic change to the rivers, as they became wider and vegetation along the channel margin and floodplain was destroyed. Management changes in 1997 and 2004 reduced the amount of water and sediment added to the river. In this study, we sought to understand how Sixth Water and Diamond Fork changed in the past and what the implications are for the future. We used data from a variety of sources to describe how and why the river changed in the past. Our resu...
A recent study reported considerable sediment trapping by three large channel bars downstream 18–28 km of the Mississippi–Atchafalaya River diversion (commonly known as the Old River Control Structure, ORCS) during the 2011 Mississippi River flood. In this study, we analyzed 3-decadal morphological changes of the 10-km river channel and the three bars to elucidate the long-term effects of river engineering including diversion, revetment and dike constructions. Satellite images captured between 1985 and 2015 in approximate 5-year intervals were selected to estimate the change of channel morphology and bar surface area. The images were chosen based on river stage heights at the time when they were captured to exclude the temporal water height effect on channel and bar morphology. Using a set of the satellite images captured during the period of 1984–1986 and of 2013–2014, we developed rating curves of emerged bar surface area with the corresponding river stage height for determining the change in bar volume from 1985 to 2013. Two of the three bars have grown substantially in the past 30 years, while one bar has become braided and its surface area has shrunken. As a whole, there were a net gain of 4,107,000 m 2 in surface area and a net gain of 30,271,000 m 3 in volume, an equivalent of approximately 36 million metric tons of sediment assuming a bulk density of 1.2 t/m 3. Sediment trapping on the bars was prevalent during the spring floods, especially during the period of 1990–1995 and of 2007–2011 when large floods occurred. The results suggest that although revetments and dikes have largely changed the morphology of the channel and the bars, they seem to have a limited impact on the overwhelming trend of sediment deposition caused by the river diversion.