HR: 1340h
AN: B43C-0296    [Abstracts]
TI: Physical Modeling of Particulate Wash-off from Rough, Impervious Surfaces
AU: * Shaw, S B
EM: sbs11@cornell.edu
AF: Cornell University, Riley-Robb Hall, Ithaca, NY 14853
AU: Lebowitz, M E
EM: mel38@cornell.edu
AF: Cornell University, Riley-Robb Hall, Ithaca, NY 14853
AU: Walter, M T
EM: mtw5@cornell.edu
AF: Cornell University, Riley-Robb Hall, Ithaca, NY 14853
AB: Current urban water quality models rely on empirical, catchment-scale functions of particulate wash-off that do not clearly represent the governing physical erosion and transport processes. We proposed a saltation-type wash-off model in which particles are repeatedly ejected from an impervious surface by raindrop impacts and are transported laterally by overland flow while settling back to the surface. The rate that particles are ejected is proportional to rain intensity, the spatial density of particles on the surface, and the surface roughness. The roughness results in enhanced particle "entrapment" by way of two mechanisms; the effective raindrop impact area is reduced and particles at the bottom of a roughness element are shielded by overlying particles. We tested our model against experimental data from small flume experiments as well as plot scale parking lot experiments. For the flume experiments, we used both an ideal uniformly rough surface and a real parking lot surface, i.e. casts of asphalt surfaces. To quantify roughness, two properties were directly measured as functions of depth: average cavity diameter and total cavity horizontal cross-sectional area. Rainfall rates, upslope overland flow rates, and initial particle amounts were varied among experiments. The model predictions agreed well with the experiments (R2 > 0.85). This work provides a basis for developing new, uniquely mechanistic models for predicting "wash-off" from urban surfaces.
DE: 1815 Erosion
DE: 1847 Modeling
SC: Biogeosciences [B]
MN: Fall Meeting 2005