Analysis of Flood Hazard Alteration: Cascading Effects of Earthquake on Stormwater Collection Network

Abstract

Earthquake can alter flood hazard in a region by impacting the components of stormwater drainage system. A methodology is proposed in this paper to measure flood hazard alteration after an earthquake. The study mainly focuses on flood hazard alteration as a result of the direct impact of an earthquake on a minor drainage system. A minor drainage system is the stormwater collection network where the components such as pipelines and inlets are vulnerable to earth movements. Cracks and breaks are considered as the impacts of earthquake on the pipelines, whereas inlet blockage because of earthquake-generated debris is considered as the impact on the network inlets. The methodology is applied on an entire midsize city to prove its scalability. The minor drainage system of the city is comprised of 564 pipes with the total length of 40 km (25 mi). The pipes are divided into 35 subcatchments, which serve a total area of 6.2 km2 (2.4 mi2) of the city. Several metrics for flood hazard alteration are defined and measured for the case study, which clearly shows alteration of the flood hazard after the earthquake. The metrics are presented in both spatially variable and aggregated formats. Such analysis can help communities to better prepare for possible alteration in flood hazard after an earthquake, to better plan and allocate resources for recovery of the stormwater collection network after an earthquake, and to recognize new flood hazard hot spots.