Storm Sewer Design Sensitivity Analysis Using ILSD‐2 Model

Abstract

The effects of the time distribution of design rainfall, the method of overland flow hydrograph generation, and the technique of flow routing through sewers on the least-cost storm sewer system design generated by the ILSD-2 Model were investigated. Ten shapes of hyetograph were used independently with three different methods to generate overland flow hydrographs for the inlets of a case study sewer system. In each case, five different techniques were used to route the flow through the sewer system, which was designed using the ILSD-2 Model. Each design was evaluated in terms of its total cost and maximum sewer risk of failure. The risk of failure was considered as the probability of having a flow imposed on a sewer exceeding the capacity of the sewer. It was found that the total cost of the sewer system design and the sewer risk associated with the design can vary significantly with the method utilized to construct the hyetograph, to generate the overland flow hydrographs, and/or to route the flow through sewers.