Runoff Characteristics for Construction Site Erosion Control Practices

Abstract

Controlling soil erosion during and after construction is a major concern due to the impacts of sediment on stream water quality, and many studies have focused on the effectiveness of erosion control best management practices (BMPs) to prevent erosion. However, their ability to reduce runoff volume and peak discharge is not commonly studied or integrated into storm water designs due to lack of data and design guidelines. This study investigated runoff characteristics (total runoff, peak flow rate, curve number, and rational method runoff coefficient) from bare compacted soil conditions with and without erosion control BMPs, with an emphasis on compost erosion control blankets (CECBs), at three different slope (2H:1V, 3H:1V, and 4H:1V). Experiments were performed in the San Diego State University, Soil Erosion Research Laboratory on a 3-m by 10-m indoor titling soil bed using simulated rainfall based on conditions specified in ASTM D-6459. Eleven erosion control BMPs were evaluated at a slope of 2H:1V, three at 3H:1V, and three at 4H:1V. The variations in slope were used to assess the effects of slope and CECB thickness on runoff. The results from this study provide new insight regarding the runoff characteristics from bare soil and erosion control BMPs that can be used to improve construction-site storm water design. The results show that 2.5- and 5.0-cm-thick CECBs on top of netting or an excelsior fiber blanket provided a significant reduction in runoff relative to the bare soil and the other BMPs (e.g., 1.3-cm CECBs, other blankets) due to water storage within the CECB, the mass of the CECB providing a strong bond between the soil surface and the bottom of the blanket reducing the potential for flowing water from coming in contact with the soil surface, and the netting/blanket under the CECB providing additional friction that helps keep the CECB from sliding down slope. The results show that slope impacts on runoff are minimal but that as CECB thickness increases runoff was reduced due to the added storage within the blanket. The results from this study can be used to aid in the selection of CECB thickness and to assess the effects of CECBs on runoff for more efficient cost effective storm water designs.