Evaluation of Erosion Control Practices Using Rainfall Simulation on 4:1 Slopes across Various Soil Types

Abstract

Construction sites rely on erosion control practices to protect bare slopes and prevent soil loss. This study used large scale rainfall simulators to evaluate various erosion control methods commonly used by the construction stormwater industry on construction sites. The study included the testing of erosion control practices on three different soil types (i.e., clay, sand, and loam) on a 4:1 slope. All testing and data collection is in accordance with ASTM D6459-19, the standard test method for testing Rolled Erosion Control Products (RECP) performance in protecting hillslopes from rainfall-induced erosion. This ASTM method is a full-scale performance assessment of the amount of soil lost on a slope in a storm with varying intensity. Some key aspects in this standard include calibration of equipment, preparation of test plot, documentation of RECP to be tested, installation of RECP, performance of test, collection of runoff and associated sediment yield, analysis of the resultant data, and reporting. In accordance with ASTM D6459-15, the rainfall simulators produced a storm of varying 20-minute increments of 2 in./hr (5.08 cm/hr), 4 in./hr (10.16 cm/hr), and 6 in./hr (15.24 cm/hr). The simulator achieved a natural raindrop size and distribution according to calibration techniques outlined in the standard. Runoff volume and sediment concentration samples were recorded throughout the test. The total sediment lost during the test was collected and recorded for each rainfall intensity interval. Testing for this project began by conducting bare soil tests to analyze the amount of sediment lost without the use of erosion control methods. A total of nine bare soil tests on the 4:1 test plots were performed with an average total soil loss of 1,977 lbs (897 kg), 236 lbs (107 kg), and 114 lbs (52 kg) for sand, loam, and clay, respectively. The average K-factor for each soil type is calculated to be 0.37 (sand), 0.043 (loam), and 0.013 (clay). Nine loose straw tests were performed on the 4:1 plots with an average total soil loss of 44 lbs (20 kg), 7 lbs (3 kg), and 17 lbs (8 kg) for sand, loam, and clay, respectively. Loose straw testing indicated substantial soil loss reduction with average C-factor values of 0.021, 0.047, and 0.193 for sand, loam, and clay applications, respectively. Nine single net straw blanket tests were performed with an average total soil loss of 80 lbs (36 kg), 20 lbs (9 kg), and 17 lbs (8 kg) for sand, loam, and clay, respectively. Single net straw testing indicated less soil loss reduction than loose straw with average C-factor values of 0.042, 0.131, and 0.31 for sand, loam, and clay applications, respectively. In addition to analyzing practice effectiveness, a statistical analysis along with a comparison of soil loss models (RUSLE and MUSLE) were performed.