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Title: Validation of bed-load transport measurements with time-sequenced bathymetric data

item ABRAHAM, D - Us Army Corp Of Engineers (USACE)
item Kuhnle, Roger
item ODGAARD, A - Us Army Corp Of Engineers (USACE)

Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2010
Publication Date: 1/1/2011
Citation: Abraham, D., Kuhnle, R.A., Odgaard, A.J. 2011. Validation of bed-load transport measurements with time-sequenced bathymetric data. Journal of Hydraulic Engineering. 137(7):723-728.

Interpretive Summary: Accurate determinations of the rate of sediment being moved in streams and rivers are necessary because the sediment may fill reservoirs and reduce their capacity, may fill channels and cause flooding, may degrade water quality, and may cause instability of the channel banks which can cause the destruction of valuable agricultural and other lands. During water flow the sediment bed of many streams becomes molded into a series of high and low features (dunes) which vary dramatically in size and shape across and down the channel. These dunes greatly affect the amount of sediment carried in the water column and on the bottom of the stream. They also affect the depth of flow in the channels during runoff events. Using a new technique, the rate at which the sediment bed is scoured by dunes, determined by a sequence of measurements of the bed elevation over dunes, has been converted to the rate of movement of the sand bed material in a stream or river. To test this method under controlled conditions, measurements of bed elevations in a sand bottomed laboratory channel were used to calculate the rate of sediment movement caused by the flowing water. These values were compared to measurements of the bed material movement determined from an independent method. This test of this new method demonstrated that it generates accurate bed movement rates and will be a valuable new method to use to improve information on sediment movement in the streams and rivers of agricultural and other watersheds.

Technical Abstract: Advances in bathymetric data acquisition have made it possible to adopt a new, expedient method for measuring bed load transport in rivers. The method consists of comparing time sequenced bathymetric data sets and utilizing a simple mass conservation relation for bed load transport. Assuming a triangular bed form shape (dune), mass conservation yields a scour rate of the upstream face of the bed form that is twice the rate of the bed load transport. Using this relation, bed load transport is calculated directly from the difference between sequential measurements of the scouring portions of the river bed. Following a description of the underlying theory, the method, called ISSDOTv2, was tested and validated with laboratory data. A field application is also presented, demonstrating the expediency and practicality of the method.