Multi-Hazard Risk Assessments of Water Systems, Elements in Common with Seismic, Security, and Other Risk Studies

Ballantyne, Donald (2003); "Multi-Hazard Risk Assessments of Water Systems, Elements in Common with Seismic, Security, and Other Risk Studies;" Proceedings of the third US-Japan Workshop on Water Systems for Seismic Practices, Organized by the Los Angeles Department of Water and Power, supported by the AwwaRF, August 6-8.

This risk assessment methodology is used to screen mutli-hazard risks for water systems. Multihazard risk assessment is becoming more popular as utilities try to balance the risk across multiple hazards. The Federal Government has instituted the Disaster Mitigation Act of 2000 (DMA 2000) that requires to public agencies to conduct multi-hazard assessments if they are to receive future hazard mitigation grant funding. The DMA 2000 methodology employs a similar analytical approach as that developed for water system assessment.

The methodology also has many common components with the Risk Assessment Methodology for Water (RAM-WSM) required for evaluation of he security risk to water utilities. The methodology uses a basic risk equation and quantifies value ranges for each term – hazard, vulnerability, consequences, and correlation factor. The terms are multiplied together resulting in a number representing the risk from a given hazard. Hazard risk is ranked for all hazards and/or for each facility within the system. The ranking can be used to select hazards for further more detailed analysis.

More detailed evaluations can be conducted using fault tree analyses and/or hydraulic network analyses. Benefit/cost analyses are used to justify mitigation measures.

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