Hydraulic Evaluation of Wattle Encasement Materials

Abstract

Suspended sediment in stormwater runoff can have negative environmental impacts. Construction activities are a major contributor to sediment-laden runoff caused by the constant disturbance and destabilization of soil. Wattles are one of the most commonly used materials across a wide range of erosion and sediment control applications. Past research has found that the hydraulic performance of wattles is based primarily on fill material. This research focused on further evaluating wattles by assessing the impact that encasement material (e.g., netting, socking, etc.) has on hydraulic performance. Two separate hydraulic flumes were used in a two-phased approach. Phase I evaluated wattle encasement fabric configurations. Selected encasements were then evaluated in Phase II using 4.0 ft (1.2 m) excelsior fill materials: plastic netting (control), polypropylene, polyester and polypropylene mix, and cotton woven encasements. The results from each wattle test were normalized with impoundment length and depth ratios. Results indicated that the percent open area (POA) had a direct relationship with the impoundment length and depth when the encasements were evaluated independently of the fill material, but encasement type had a larger effect on performance when fill material was included. Using a cotton fabric increased impoundment length and depth ratios by 30% and 24%, respectively, which increased to 52% and 42%, when two additional cotton fabric layers encompassed the wattle.