Risk Analysis and Management of Water Distribution Networks Due to Probable Earthquake

Abstract

Water distribution network (WDN) is one of the infrastructures which provide welfare and comfort for people in their life. This role is magnified in critical situations like earthquake occurrence since WDN will suffer from breaks and leakages. Efforts to lessen the impact of earthquake are on reducing both the extent and the severity of damage, and the time to restore service given by WDN. Thus, for understanding exact damages, the key role of accurate analysis in both seismic and hydraulic terms is not negligible. In this study, pipeline damage caused by seismic wave propagation is modeled using relationships obtained from the 1994 Northridge earthquake. The time of repairs in WDNs is calculated regarding accurate hydraulic analysis based on the head-driven simulation method. Additionally, a suitable index is introduced which can show the effect of repairs on nodal pressures during repair process. After defining new terms for risk assessment on the basis of Federal Emergency Management Agency (FEMA) method, this approach is applied to a part of Tehran’s WDN to assess the capabilities of the proposed model. Since there is no special damage relationship for Iran, some available damage relationships were applied to a part of Tehran’s WDN and results showed that HAZUS (Washington D.C. Department of Homeland Security Emergency Preparedness and Response, FEMA, Mitigation Division, New York, 2003) relationship predicted more damages. In other words, the highest risk, the largest number of accidents (pipe bursts, pipe disengagement and pipe leakage) and the maximum value of restoration time were obtained from HAZUS (2003) relationship. Two risk mitigation scenarios were defined to assess the response of water supply system to earthquake impacts including decreasing demand and use of wells. Results showed that decreasing demand by 20% leads to decrease in risk, so that the maximum decrease was calculated in the case of using O’Rourke and Jeon damage relationship (risk decreased from 1.01 × 10−5 to 8.26 × 10−6). But using wells after earthquakes can be more effective on decreasing risk after earthquake. Outcomes from case study express that this model can be applied to every city having both earthquake catalogue and WDN’s model to show number of failures and leaks in pipes, risk of each repair rate relation and pressure index for earthquake scenarios.