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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #312862
Title: Development of bankfull hydraulic geometry relationships for the physiographic divisions of the United States

Author
item BEIGER, K - Texas Agrilife Research
item RATHJENS, H - Purdue University
item ALLEN, P - Baylor University
item Arnold, Jeffrey

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2014
Publication Date: 6/9/2015
Publication URL: http://handle.nal.usda.gov/10113/5451331
Citation: Beiger, K., Rathjens, H., Allen, P.M., Arnold, J.G. 2015. Development of bankfull hydraulic geometry relationships for the physiographic divisions of the United States. Journal of the American Water Resources Association. 51(3):842-858.

Interpretive Summary: Hydrologic and water quality models are currently used for regional and national conservation and environmental assessment in the U.S. and around the world. An important input to these models is river geometry, including width and depth. In this study, regional regression equations for river width, depth, and cross-sectional area were developed as a function of drainage area. Equations were developed for different ecoregions or physiographic divisions of the U.S. Results showed that the regional equations produced more accurate river geometry than the nationwide curves currently used in national conservation and environmental assessments. The improvement in data will provide more accurate model output and ultimately sound national conservation policy.

Technical Abstract: Bankfull hydraulic geometry relationships are used to estimate channel dimensions for stream flow simulation models, which require channel geometry data as input parameters. Often, one nationwide curve is used across the entire U.S. (e.g. in SWAT), even though studies have shown that the use of regional curves can improve the reliability of predictions considerably. In this study, regional regression equations predicting bankfull width, depth, and cross-sectional area as a function of drainage area are developed for the Physiographic Divisions and Provinces of the U.S. and compared to a nationwide equation. Results show that the regional curves are more reliable than the nationwide curve in almost all Physiographic Divisions of the U.S. Reliability of the curves depends largely on the number of observations per region and how well the sample represents the population. Regional regression equations developed at a finer spatial scale (Physiographic Provinces) yield better results than those developed for the Physiographic Divisions in some but not all cases. It is also likely that regional curves can be improved by using multiple regression to incorporate additional explanatory variables. Results also show that drainage area is a less reliable predictor of bankfull channel dimensions than bankfull discharge.