Location: Watershed Physical Processes ResearchTitle: Bed-load validation for ISSDOTv2
|MCALPIN, TATE - Us Army Corp Of Engineers (USACE)|
|JONES, KEATON - Us Army Corp Of Engineers (USACE)|
|ABRAHAM, DAVID - Us Army Corp Of Engineers (USACE)|
Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2021
Publication Date: 1/5/2022
Citation: Mcalpin, T.O., Wren, D.G., Jones, K.E., Abraham, D.D., Kuhnle, R.A. 2022. Bed-load validation for ISSDOTv2. Journal of Hydraulic Engineering. 148(3). https://doi.org/10.1061/(ASCE)HY.1943-7900.0001968.
Interpretive Summary: The movements of sand dunes in large rivers are used to measure how much sand moves downstream in rivers. The amount of sand that moves down rivers is used to determine how the rivers are affected by changes to the river channel. Due to the depth of large rivers and the way that sand movements vary across and along them, rates cannot be measured accurately by collecting physical samples of sand and water. Using acoustic methods, which are similar to sonar used in submarines, the shape of the river bottom can be measured multiple times in the same day, and the change in shape can be used to calculate how much sand is moving. The Integrated, Section Surface Difference Over Time, version 2 (ISSDOTv2) method was developed by the U.S. Army Corps of Engineers to use measurements of the river bottom to calculate the sand transport rate in large rivers. Since it is not possible to check the method directly in a river, laboratory experiments used other methods to measure the rate of sand movement to check the results of the ISSDOTv2 method and to estimate how close the ISSDOTv2 results are to the real amount of sand being moved by a river. This step is necessary step before the method can be used more broadly for river management. As a result of this work, the accuracy of sand transport measurements will be improved, and the ISSDOTv2 method will be useable by more river engineers, which will improve the nation’s management of large rivers.
Technical Abstract: Bed-load transport is an important process impacting riverine morphology, but until recently it has proven to be difficult to measure in large sand bed rivers. The Integrated, Section Surface Difference Over Time, version 2 (ISSDOTv2) method provides a means of quantifying the bedload in large sand bed rivers with associated uncertainty bounds. A series of flume experiments, which included frequent measurements of bed topography and an independent measurement of bedload across a range of flows, was used to provide validation and uncertainty estimates for the ISSDOTv2 method. As compared to the estimated bedload, the mean error in the ISSDOTv2 calculations was 5.6% (high flow), 12.9% (medium flow), and 56% (low flow), indicating improved accuracy for higher flow and transport conditions. Across all flow rates, the uncertainty for bed-load measurements using the ISSDOTv2 method was approximately +/- 50%. It was also found that the ISSDOTv2 method responded appropriately to step-down flows, as indicated by agreement between ISSDOTv2 load results and accompanying independent measurements of bedload.