ERDC/CHL CHETN-VII-4
June 2002
Quantification of Bed-Load Transport
on the Upper Mississippi River
Using Multibeam Survey Data
and Traditional Methods
by David D. Abraham and Thad Pratt
progress made in using multibeam bathymetric data to determine bed-load transport in large sand
bed rivers. Work was conducted as part of the Monitoring of Completed Navigation Projects
(MCNP) Program in coordination with the Coastal Inlets Research Program (CIRP).
INTRODUCTION: The need for quantifying bed-load transport is universal in riverine and coastal
processes. In the past many analytic and mechanical methods have been devised to try and quantify
bed-load transport on large sand bed rivers. To date, most methods are only marginally successful.
In this MCNP work unit, being able to quantify the bed load accurately would be extremely helpful
in determining whether or not river training structures in combination with a drawdown of the
navigation pool would have an effect on net sediment movement through a given reach of river. In
other words, accurate measurements would help resolve whether or not the altering of the pool stage
and flow schedules might also be used as a sediment management tool. With these considerations in
mind, a new methodology for the computation of bed-load transport was developed using multibeam
bathymetric data. This methodology could also be applicable in evaluating transport in and around
coastal structures throughout a tidal cycle.
MEASUREMENT METHOD: Two methods were initially conceived. One would be based on the
celerity of the traveling sand waves, the other on the difference of surfaces. At this writing, the
surface difference method was pursued and implemented. It is called the Integrated Surface
Difference Over Time (ISDOT) technique. The method processes multibeam data and quantifies a
bed-load transport rate for a given river cross section. This is accomplished by taking at least two
sets of bathymetric data, at different times, for the same spatial location. The two data sets are
interpolated to a spatial grid and a difference plot is produced. Incremental volumes are calculated
and summed over the entire cross section. The total volume change with time, when multiplied by
the density of the water sediment mixture, yields a mass transport rate.
As of this date the method is still in the developmental stage, but has shown surprisingly close
results with some of the other standard estimation methods. The method of wave celerity, previously
mentioned, might prove more reliable if worked out, but presents more computational obstacles than
the ISDOT method. In this technical note, only the ISDOT method is considered.
DEFINITIONS: For purposes of defining the limitations and applicability of the ISDOT method,
the following definitions of bed load are considered: Einstein (1950); Colby (1963); Bagnold
(1966); van Rijn (1984). At first glance all these seem to define bed load in similar terms. That is,
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