An experimental study on the hydraulics of stormwater inlets

A series of laboratory experiments was performed to investigate the hydraulic performance of stormwater inlets. The results indicate that at the transition regime and for the maximum street slope, the addition of the second inlet increased the inlet discharge by 52% and 72% for cross-slopes of 2% and 4%, respectively. The normalized inlet discharge decreased non-linearly with the approaching water head in the weir flow regime while it linearly increased in the orifice flow regime. The effect of street slope was more pronounced in the orifice flow regime and prediction models were proposed to estimate inlet discharge for different road grades and cross-slopes. The boundary between weir and orifice flow regimes was identified for each stormwater inlet design and it was found that the cross-slope shifted the boundary more towards the orifice flow regime. It was observed that the peak efficiency decreased with increasing road grade.