Investigating Urban Drainage System Robustness Using Multi-Storm Design Approach

Traditional urban drainage system design typically relies on a single design storm, which may not adequately capture the range of potential rainfall patterns. This study builds upon previous research investigating the effects of hyetograph shape variability by introducing a multi-storm design approach. We examined the robustness of urban drainage system designs by comparing systems developed using single and multiple design storms. Our methodology involved investigating model responses to an ensemble of 1000 hyetographs with varying temporal patterns but consistent duration and total precipitation. Students designed systems using a computer model, optimizing pipe dimensions, retention basin volume, and weir dimensions while minimizing costs and preventing flooding. We compared designs created with one versus three design storms. Results revealed that systems designed with three design storms showed lower flooding and overflow volumes, with average reductions of 75% and 35% respectively compared to single-storm designs. However, the overall system robustness was only marginally enhanced. This research highlights the limitations of current urban drainage system design approaches and suggests the need for more comprehensive methodologies to address climate variability and design uncertainty.