A Field Examination of Rolled Erosion Control Systems and Their Influence on Runoff and Sediment Transport

摘要

An erosion control field study was conducted on a highly erodible Molokai Oxisol in Hawaii, with a slope of 9precent. A side-by-side bounded plot was installed at the field site, and each plot segment had an area of 3.2m~2. A mean rainfall intensity of 35 mm h~(-1) was applied during all experiments by a computer-controlled rainfall simulator. During all events, runoff and sediment were sampled at the time of runoff initiation and every 5 min thereafter for a period of two hours. Plots were continually observed during storm events and the following measurements were recorded: time to runoff initiation, time to rill incision, rill migration rates and rill dimensions. Ten rolled erosion control systems (RECS) were examined, including seven dominantly "natural" systems, three synthetic systems, and a bare control surface treatment. Most RECS examined delayed time to runoff generation compared to the bare treatment; however, only minor differences in runoff coefficient were noted under equilibrium flow conditions. Despite minimal differences in runoff, systems differed in their temporal effectiveness in reducing sediment yield, but all performed better than the bare treatment. Based on sediment yield reduction, distinct rolled erosion control system groupings were identified. The two most effective ERCS were "natural" products, one being a 100precent conconut mattress fiber matrix system (C125), and the other was dominantly composed of pure wood fiber hydromulch with a small percentage of recycled synthetic fibers (Futerra). The two least effective products were an open weave coconut fiber system (BioD-Mat 40) and a system composed of high density randomly oriented PVC fibers (PEC-MAT). Several cardinal properties were found to be directly related with erosion rates. Rolled erosion control systems with randomly oriented fibers and significant three-dimensionality outperformed open weave systems. Open-weave systems with flexible fibers were more effective in reducing erosion and dampening the rate of rill expansion once rilling had been initiated. For a given fiber type, as the percentage of surface cover of an open-weave system increases erosion rates decrease. These findings provide significant insights for future development of rolled erosion control systems.