Development Of A Storm Runoff Simulator: Part 1 – Design Considerations

Abstract

Evaluation of conservation buffers has relied primarily on small-scale plot (30 to 50 m2) studies with a limited range of buffer widths and field to buffer area ratios (BARs). Most studies used simulated runoff at steady flow rates. There is a need to evaluate conservation buffers installed at NRCS design widths and BARs to assess how well in-field buffers reduce nonpoint source pollution, especially for unsteady flow. The goal of this project is to develop a storm runoff simulator to distribute variable flow rates and contaminant concentrations across the upslope end of a buffer in a reproducible fashion. The simulator design should allow for easy transportation and adaptability to terrain and resource constraints found in the field. The SCS CN Method and the MUSLE were used to evaluate eight alternative combinations of BAR and buffer size. Buffer size ranged from 30 to 67.5 m2. Given the design constraints of less than 1 metric ton of soil per simulation, only a 1- 9-m plot size met the design criteria. Based on realistic constraints of a 7580-L available water supply, the final design constraints included a 7.3-L s-1 peak flow rate and 0.71 tons of soil, for a 1- 9-m plot, which allowed for BARs up to 49:1.