Influence of particle size on wet pond effectiveness

A 5 670-m(2) wet detention pond draining a predominantly residential urban area was monitored for flow, suspended solids, bedload, particle-size distribution, and selected pollutants during 16 storm events. Both suspended solids concentrations and particle-size distribution of the suspended solids in runoff water exhibited large variations between storms. Though a portion of particles larger than the pond's critical particle size left the pond, the pond removed 87% of the total suspended solids entering the pond. The relative proportion of clay-size particles increased from 36 to 72%. Sand-and silt-size fractions both decreased. Heavier particulate material saltating along the channel bottom, termed bedload, composed an average of 14% of the total particulate mass or load to the pond. The pond's sediment and associated pollutant removal efficiencies were influenced by influent particle-size distribution.