The Impact of Leaf Litter on the Performance of Catch Basin Inlets

A full-scale model roadway was constructed at the Ocean, Coastal and River Engineering Research Centre of the National Research Council Canada (NRC-OCRE) in Ottawa, Canada, to measure the conveyance capacity of catch basin inlets. A total of 178 tests were performed with the primary goal of measuring the impact of leaf litter on conveyance in both ponding and flow through conditions. The inlet studied was a rectangular inlet design that is surface mounted and follows the profile of a 10 cm high rolled curb which was used in the study. Incident water depths ranging from 0.002 to 0.366 m were examined and the model roadway was tested in various orientations in flow through conditions with a 2.0% cross-slope and road grades ranging from 0.5% to 5.0%. The maximum flow reduction observed in the study was for the ponding or sag tests where the initial leaf litter obstructing approximately 95% of the inlet resulted in a conveyance which was only 35% of the unobstructed value. This work aims to assist municipalities in understanding the performance of their storm water management systems and inform where limited infrastructure funds should be allocated in order to adapt to increasingly severe urban flooding.