Field investigation of compost blankets for erosion control under concentrated flow conditions.

摘要

Compost blankets are recognized as an effective erosion control practice that has been utilized widely. While previous studies have proven that compost blankets can control erosion as well or better than traditional methods under normal rainfall and sheet flow conditions, little attention has been paid to how compost will respond to concentrated flow conditions. The objective of this research was to investigate erosion processes on compost blankets under concentrated flow conditions. Erosion control compost (ECC), yard waste compost (YWC), and a bare soil (BS, loam) were studied using four concentrated flow rates on 12.5% slope plots. Time to initiate discharge, flow velocity, solids concentration, and total loss of solids were measured. The erosion process and rill evolution under these conditions were observed and recorded. Results indicated that the time elapsed to commence discharge from compost plots was significantly longer than that from soil plots. Large amounts of inflow were able to infiltrate into the compost matrix and flow through it, leaving a smaller portion of surface flow on compost plots than on soil plots. Under high inflow rates (2.7x10-4 and 3.3x10-4 m3/s), solids loss from compost plots was significantly less than those from soil plots. Under a same inflow conditions, average solids concentrations were significantly lower on compost plots than on soil plots, as deposition occurred in compost rills. Deposited solids often formed micro-dams in the compost rills, which further promoted flow through the compost matrix and deposition of suspended particles. The formation of micro-dams in compost plots was an important mechanism in preventing soil erosion under concentrated flow conditions. Results of this study indicated that the erosion process on compost blankets may differ from classical shear-induced rill erosion on soil surfaces. Future work will investigate models that may be used to better understand and predict erosion of compost material under concentrated flow conditions.