TY - JOUR
T1 - Net local removal of floodplain sediment by river meander migration
AU - Lauer, J. Wesley
AU - Parker, Gary
N1 - Funding Information:
We would like to thank Chris Paola for his help designing the study and for insightful comments on an early revision of the manuscript. We would also like to thank Swappan Sahoo, Matthew Kirwan, Scott Wright, Miguel Wong, Dylan Blumentrit, and Alessandro Cantelli for help in the field. We are grateful to Dakota County, MN for providing the LiDAR survey data along the Vermillion River. This material is based upon work funded by the NSF under agreements CTS-0096916 and EAR-0203296, as well as the STC program under agreement EAR-0120914. Special thanks are due to the National Science Foundation's National Center for Earth Surface Dynamics, which provided additional funding and equipment, and to Saint Anthony Falls Laboratory at the University of Minnesota, where much of this work was performed.
PY - 2008/4/1
Y1 - 2008/4/1
N2 - Erosion from the banks of meandering rivers causes a local influx of sediment to the river channel. Most of the eroded volume is usually replaced in nearby point bars. However, the typical geometry of river bends precludes the local replacement of all eroded material because (i) point bars tend to be built to a lower elevation than cutbanks and (ii) point bars tend to be shorter than the eroding portion of cutbanks because of channel curvature. In a floodplain that is in equilibrium (i.e., neither increasing nor decreasing in volume), sediment eroded from cut banks must be replaced elsewhere on the floodplain. The local imbalance caused by differences in bank height should be balanced primarily by overbank deposition, while the local imbalance caused by curvature should be balanced primarily by deposition in abandoned stream courses or oxbow lakes. Estimates of these local imbalances based on remotely sensed measurements of bank geometry and channel migration have been made on four systems in the United States: a 91-km reach of the Pearl River in Louisiana and Mississippi, a 62-km reach of the Bogue Chitto River in Louisiana, a 35-km reach of the Neuse River in North Carolina, and a 2.7-km reach of the Vermillion River in Minnesota. For these systems, the total local imbalance, integrated over many bends, ranged from 0.36 to 2.27 m3/yr/m of valley length (0.15 to 1.32 m3/yr/m of channel length), or 7 to 45% of gross cutbank erosion, with a typical value of about 17%. When compared with gauged suspended sediment data, the measurements provide estimates of the relative importance of floodplains for storing material transported by a river system. The data suggest that even if the studied systems are near long-term mass balance equilibrium (as opposed to undergoing net deposition or erosion), almost all of the sand and in some cases much of the silt and clay in transit through these systems is likely to have spent some time stored in an upstream floodplain.
AB - Erosion from the banks of meandering rivers causes a local influx of sediment to the river channel. Most of the eroded volume is usually replaced in nearby point bars. However, the typical geometry of river bends precludes the local replacement of all eroded material because (i) point bars tend to be built to a lower elevation than cutbanks and (ii) point bars tend to be shorter than the eroding portion of cutbanks because of channel curvature. In a floodplain that is in equilibrium (i.e., neither increasing nor decreasing in volume), sediment eroded from cut banks must be replaced elsewhere on the floodplain. The local imbalance caused by differences in bank height should be balanced primarily by overbank deposition, while the local imbalance caused by curvature should be balanced primarily by deposition in abandoned stream courses or oxbow lakes. Estimates of these local imbalances based on remotely sensed measurements of bank geometry and channel migration have been made on four systems in the United States: a 91-km reach of the Pearl River in Louisiana and Mississippi, a 62-km reach of the Bogue Chitto River in Louisiana, a 35-km reach of the Neuse River in North Carolina, and a 2.7-km reach of the Vermillion River in Minnesota. For these systems, the total local imbalance, integrated over many bends, ranged from 0.36 to 2.27 m3/yr/m of valley length (0.15 to 1.32 m3/yr/m of channel length), or 7 to 45% of gross cutbank erosion, with a typical value of about 17%. When compared with gauged suspended sediment data, the measurements provide estimates of the relative importance of floodplains for storing material transported by a river system. The data suggest that even if the studied systems are near long-term mass balance equilibrium (as opposed to undergoing net deposition or erosion), almost all of the sand and in some cases much of the silt and clay in transit through these systems is likely to have spent some time stored in an upstream floodplain.
KW - Bank erosion
KW - Floodplains
KW - Grade
KW - River meandering
KW - Sediment budgets
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U2 - 10.1016/j.geomorph.2007.08.003
DO - 10.1016/j.geomorph.2007.08.003
M3 - Article
AN - SCOPUS:44449171774
SN - 0169-555X
VL - 96
SP - 123
EP - 149
JO - Geomorphology
JF - Geomorphology
IS - 1-2
ER -