Estimating the Sediment Yield Due to Bend Migration in Meandering Rivers
Abstract
Management of sediment in rivers is a major element of the sustainable use of natural watercourses. In the United States this is addressed through Regional Sediment Management (RSM). To be effective, RSM needs data on sediment inputs to the fluvial system, including that from bank erosion, which may account for as much as 75% of the load. In this research, a database of 1,512 meander bends on rivers in the USA was used to supply information on bend migration rates over 20- to 60-year periods. Statistical analysis was performed on the bend migration data to explore the relationship between the bend planform at the beginning of each monitoring period (represented by R/w = the ratio of bend radius to channel width) and the average rate of bend migration (represented by E/w = the ratio of the average annual retreat of the outer bank to the channel width). A probability analysis was used to derive a series of curves for E/w as a function of R/w for probabilities of the expected rate of erosion not being equaled or exceeded ranging from 10% to 99%. This analysis provides the basis for predicting the rate of bank erosion due to bend migration with a user-selected probability of the rate not being equaled or exceeded. Prediction of the volume of bank sediment input to the watercourse due to bend migration also requires estimation of the average height of the eroding bank and the length of channel along which erosion occurs. The eroding bank height may be estimated using an algorithm developed in previous research performed for the USACE for average scour depth at the outer margins of meander bends (Thorne et al. 1995). The length of eroding bank may be estimated from field observation or using expert judgment based on consideration of the Brice data set (Soar and Thorne 1999). Methods to make these estimates are presented to enable users to predict the volume of sediment derived from bank erosion due to bend migration in single-thread, alluvial, meandering rivers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2007
- Accession Number
- ADA476212
Entities
People
- Colin Thorne
- Salam Sikder