Open-File Report 2009–1260
![]() AbstractDam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability, floodplain inundation patterns, and channel morphology. Most of the world’s largest rivers have been dammed, which has prompted management efforts to mitigate dam effects. Three high dams (completed between 1953 and 1963) occur along the Piedmont portion of the Roanoke River, North Carolina; just downstream, the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, more than 700 bank erosion pins were installed along 124 bank transects. Additionally, discrete measurements of channel bathymetry, water clarity, and presence or absence of mass wasting were documented along the entire 153-kilometer-long study reach. Amounts of bank erosion in combination with prior estimates of floodplain deposition were used to develop a bank erosion and floodplain deposition sediment budget for the lower river. Present bank erosion rates are relatively high [mean 42 milimeters per year (mm/yr)] and are greatest along the middle reaches (mean 60 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates such that erosion rate maxima have migrated downstream. Mass wasting and water clarity also peak along the middle reaches. |
First posted January 2010
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Schenk, E.R., Hupp, C.R., Richter, J.M., and Kroes, D.E. 2010, Bank erosion, mass wasting, water clarity, bathymetry, and a sediment budget along the dam-regulated lower Roanoke River, North Carolina: U.S. Geological Survey Open-File Report 2009–1260, 112 p., available only at https://pubs.usgs.gov/of/2009/1260/.
Abstract
Introduction
Study Area
Methods
Bank Erosion
Channel Bathymetry, Water Clarity, and Mass Wasting
Bank- and Floodplain-Based Sediment Budget
Results
Bank Erosion
Mass Wasting and Water Clarity
Bathymetry
Bank- and Floodplain-Based Sediment Budget
Summary
References Cited
Appendix 1: |
Summary of Bank Transect Locations, Number of Erosion Pins per
Transect, Bank Erosion Index Values, Mean Bank Height, and Erosion Rates. |
Appendix 2: |
Erosion Pin Measurements for Each of the 701 Bank Erosion Pins. |
Appendix 3: |
Cross-Sectional Survey Data by Transect, Including Bathymetry. |
Appendix 4: |
Bathymetric, Water Clarity, and Mass Wasting Data Collected on an Approximately 200-Kilometer River Survey from Near Halifax, N.C., to the Alblemarle Sound. |
Appendix 5: |
Mean Floodplain Sedimentation from 2002 to 2005 Measured Using
Feldspar Clay Pads on Transects Perpendicular to Channel. |
Appendix 6: |
Stage-Discharge Relationships at Selected USGS Streamgages, River
Stage Information Between Pin Measurement Dates, and Pin Bank Erosion
Rates Related to River Stage and Date. |