Design and Construction of a Rainfall Simulator for Large-Scale Testing of Erosion Control Practices and Products

Abstract

Soil erosion and the resulting sediment deposition constitutes one of the greatest pollutants in our nation’s waterways. Construction projects often generate large areas of exposed soil that remain disturbed throughout the duration of the project. Exposed soil, resulting from clearing, grubbing, and land grading activities, is more susceptible to erosion during a rain event due to lack of vegetative cover. Erosion control practices and products (i.e., vegetative cover, erosion control blankets, hydromulches, etc.) are an important aspect of any construction project due to their ability to limit the process of erosion. This study developed a testing apparatus capable of accurately and repeatedly simulating a 2-yr, 24-hr storm event in Auburn, Alabama with the goal of determining the performance and effectiveness of erosion control practices and products. The test protocols consisted of calibrating the rainfall simulator and validating the results through bare soil control tests. Data collection procedures consisted of recording rainfall depth in rain gauges, collecting and analyzing flour pellets for drop sizes, and suspended sediment concentration (SSC). The optimum location for each sprinkler riser as well as the most accurate nozzle configurations were determined through the test procedures developed for this study. Through calibration testing, the simulator was found to produce rainfall intensities of 1.10, 1.78, and 3.76 in./hr. Uniformity of rainfall distribution ranged from 79-81%. The rainfall simulator’s performance was also validated through three, 60 minute bare soil control tests. Results from these tests (i.e., erosion patterns, SSC) showed that consistent erosion patterns were achieved with maximum sediment concentrations ranging from approximately 55,000 – 82,000 mg/L.