DEVELOPMENT OF MODELS AND CONSERVATION PRACTICES FOR WATER QUALITY MANAGEMENT AND RESOURCE ASSESSMENTS
Location: Grassland, Soil and Water Research Laboratory
Title: Prediction of channel degradation rates in urbanizing watersheds
Submitted to: Hydrological Sciences Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 2008
Publication Date: October 1, 2008
Citation: Allen, P.M., Arnold, J.G., Skipwith, W. 2008. Prediction of channel degradation rates in urbanizing watersheds. Hydrological Sciences Journal. 53(5):1013-1029.
Interpretive Summary: In urbanizing watersheds, as land use changes, and storm sewers and impervious surfaces increase, storm runoff increases, causing stream channels to erode. The channels erode into homes and businesses causing millions of dollars of damage each year. In this study a model was developed to determine the rate at which the channel will erode. A case study of channel stability was performed in north central Texas. The new tool gives planners and decision-makers estimates of channel erosion rates and the potential impact of land use change and continuing urbanization.
In urbanizing watersheds, as land use changes, and storm sewers and impervious surfaces are increased, both the frequency and magnitude of discharge increase, resulting in stream channel down-cutting and widening and related loss of structures and engineering works. A simple model for assessing the time rate of degradation in watersheds is given. The model relies on a continuous simulation of watershed discharge based on local climate (SWAT-DEG) instead of a dominant discharge approach. Unique to this approach is the use of in situ erosion parameters derived from submerged jet tests, which give both the allowable tractive force as well as erodibility coefficients. The model is used in concert with the Watson-Harvey analysis of channel evolution. Four methods were used to verify and validate the model for estimating rates of degradation. A case study of channel stability assessment using this tool was made in north central Texas (USA). Rates of incision were nonlinear and ranged from 0–76 mm/year.