| Abstract: | This report presents the results of a study
conducted by the U.S. Geological Survey in cooperation
with the Missouri Department of Conservation
to describe the hydrology, sediment
transport, and sediment deposition along a
selected reach of Long Branch Creek in Macon
County, Missouri. The study was designed to
investigate spatial and temporal characteristics of
sediment deposition in a remnant forested riparian
area and compare these factors by magnitude of
discharge events both within and outside the measured
range of flood magnitudes.
The two-dimensional finite-element numerical
models RMA2-WES and SED2D-WES were
used in conjunction with measured data to simulate
streamflow and sediment transport/deposition
characteristics during 2-, 5-, 10-, and 25-year
recurrence interval floods. Spatial analysis of simulated
sediment deposition results indicated that
mean deposition in oxbows and secondary channels
exceeded that of the remaining floodplain
areas during the 2-, 5-, 10-, and 25-year recurrence
interval floods. The simulatedmass deposition per
area for oxbows and secondary channels was 1.1 to
1.4 centimeters per square meter compared with
0.1 to 0.60 centimeters per square meter for the
remaining floodplain.
The temporal variability of total incremental
floodplain deposition during a flood was found to
be strongly tied to sediment inflowconcentrations.
Most floodplain deposition, therefore, occurred at
the beginning of the streamflow events and corresponded
to peaks in sediment discharge. Simulated
total sediment deposition in oxbows and
secondary channels increased in the 2-year
through 10-year floods and decreased in the 25-
year flood while remaining floodplain deposition
was highest for the 25-year flood.
Despite increases in sediment inflows from
the 2-year through 25-year floods, the retention
ratio of sediments (the ratio of floodplain deposition
to inflow load) was greatest for the 5-year
flood and least for the 25-year flood. The decrease
in retention ratio at greater flows is likely the result
of higher velocities on the floodplain, resulting in
higher bed shear stress, greater suspension time of
deposited material, and greater sediment transport
through the system.
Simulated sediment deposition was most
sensitive to sediment inflow concentrations and
modification of floodplain roughness?factors
that can be controlled through management practices.
The increase in floodplain sediment deposition
resulting from a simulated increase in
vegetation density (increase in floodplain roughness
from a Manning?s n of 0.11 to 0.12) was
142,000 kilograms, or 6.5 percent for a 10-year
recurrence interval flood. This increase was comparable
to total oxbow and secondary channel depositionmass
in the simulations, but would result in
amean increase in floodplain deposition thickness
of only 0.025 centimeter. The hydrodynamic model results show the
importance of the secondary channels and meander
cutoff channels in this system because these
areas quickly bring floodwaters and sediment to
areas not close to the main channel. The meander
cutoff channels in the simulation also effectively
decrease flow and velocities in somemain channel
sections thereby affecting sediment deposition in
the vicinity of these features. |
| Genre: | USGS Numbered Series |
| ProdID: | 33039 |
| Citation Author: | Heimann, David C. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | 61 p. |
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| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 2001-4269 |
| Citation Search Results Text: | Numerical simulation of streamflow distribution, sediment transport, and sediment deposition along Long Beach Creek in Northeast Missouri; 2001; WRI; 2001-4269; Heimann, David C. |
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| Citation Year: | 2001 |
| Type: | citation/reference |
| Text: | Numerical simulation of streamflow distribution, sediment transport, and sediment deposition along Long Beach Creek in Northeast Missouri; 2001; WRI; 2001-4269; Heimann, David C. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| URL (INDEX PAGE): | http://mo.water.usgs.gov/Reports/WRIR01-4269/index.htm |
| Date Other: | Wed, 1 May 2002 00:00 -0500 |
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