Sediment Wash-Off from an Impervious Urban Land Surface

Abstract

Sediment wash-off from impervious land is believed to be related to various factors including sediment buildup, rainfall intensity, rainfall energy, runoff rate, sediment sizes, and land surface characteristics. Most previous studies have used controlled rainfall in small areas to investigate mechanisms of sediment wash-off. This paper presents sediment wash-off results from an impervious urban surface under actual accumulation and rainfall events. Two temporal scales were considered when the sediment wash-off processes were investigated. On the event scale, sediment wash-off is strongly correlated with runoff volume. On the instantaneous scale, sediment wash-off from eight rainfall events was investigated using first-order and zero-order wash-off equations. Source-limited and transport-limited wash-off processes were discussed. The wash-off process on October 10, 2002, was linearly dependent on runoff and can be described using a first-order exponential equation. The wash-off processes on May 15, 2003, and June 7, 2003, can be described using a zero-order equation. For the remaining storms, both first-order and zero-order wash-off equations can represent the wash-off processes.