Development of a Reliability Index Considering Flood Damage for Urban Drainage Systems

Abstract

Urban drainage systems are used to safely drain rainwater and prevent urban inundation, and their reliability is usually calculated from the probability of failure, which includes the probability of the drainage facilities being destroyed. This study proposes a new reliability index that includes three factors (flood volume, nodes, and damage), with the aim of prioritizing the structural and nonstructural measures required to improve urban drainage systems. In this study, synthetic rainfall data are generated by the Huff distribution and are used as input data for runoff simulations. The Distance Measure Method that uses a utopian approach is employed here to generate a dimensionless reliability index, as the three factors use different units and no definitive criteria currently exist to determine the weights that should be assigned to each factor. The reliability indexes of flood volume, nodes, and damage determined in this study are 0.7226, 0.4584 and 0.9750, respectively, as the three factors are weighted equally in the reliability index calculation. Using the new method, the reliability index of the city of Jeongup is 0.6484. The new reliability index can be used to assess the effectiveness of various flood mitigation measures in preparation for extreme rainfall events.