Abstract

This study looked at step pool stream studies, reports, and field data in five catchment areas. The areas of interest include the Rio Cordon catchment area in Italy, the Cascade Mountain Range in Washington, the Siuslaw National Forest in Oregon, various areas in California, the University of Richmond in Virginia, and the Arkansas River Basin in Colorado. The purpose of this study was to compare the flow resistance and stability after large flooding events of artificial and natural step pool sequences to potentially provide information to improve monitoring of newly installed step pools and the design of future step pool structures. To measure flow resistance, a ratio of average height of the steps divided by the average length of the pools divided by the slope (H/L/S) was used, which was determined from a previous study by Abrahams et al. (1995) to correlate with maximum flow resistance. To compare stability of the steps following flood events, observational data was collected from studies and reports on the steps used. The average H/L/S values for the artificial and natural steps were calculated to be 3.23 and 1.22, respectively. According to the ideal maximum flow resistance range of 1-2, found by Abrahams et al., the natural step pools were found to maximize flow resistance more effectively than the artificial step pools. In analyzing the observational data, 7 out of 8 artificial and 8 out of 8 natural showed signs of instability following flood events. So, while natural step pools were better at maximizing flow resistance, they were not necessarily more stable than artificial step pools. This provides evidence that there are potentially other factors that contribute to the instability of step pools including the size of the flooding and increased sediment transport from upstream.

Paper prepared for the Environmental Studies Senior Seminar.

Faculty Advisor: Dr. Todd Lookingbill

Document Type

Unpublished Paper

Publication Date

4-30-2020

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