The impact of bar grate extremal clogging on the discharge capacity of stormwater inlets in orifice mode.

Abstract

The rapid growth of urbanisation and the increasing intensity of extreme rainfall events have heightened the risk of overloading stormwater drainage systems worldwide. This study presents new experimental insights into the hydraulic performance of bar grate sump inlets operating in unsubmerged orifice flow mode under extreme clogging conditions. Four grate configurations were tested, with clogging levels reducing the effective open area by 92.5-96.8%. A notable trend was observed across all configurations: orifice discharge coefficient (C_o) increased with higher clogging ratios. This relationship was expressed through a two-parameter exponential function linking C_o to the total open-area ratio. The findings highlight the importance of context-specific assessment of inlet performance, especially for non-standard or heavily clogged urban drainage structures. By extending the experimental range beyond typical clogging levels considered in previous studies, this research contributes to a better understanding of inlet hydraulics and provides a practical reference for improving the resilience of urban drainage systems facing extreme events.