*4.4. Risk and Resilience Management*

A small number of studies worked on methods to support risk and resilience management. Moraitis et al. [110] describes a methodology to quantify the impact of cyber–physical attacks on water distribution networks. The methodology is based on quantifying failures described under categories (magnitude, propagation, severity, crest factor, rapidity) against user-defined service levels. A proposed model is demonstrated using the C-Town WDN.

Jeong [111] discusses the development of a risk management framework for water infrastructure against intentional attacks, including cyber-attacks based on vulnerability assessment and consequence assessment of attacks. The proposed vulnerability assessment involves the development of a hierarchical structure of the system to identify all water infrastructure components, using expert knowledge and fuzzy hierarchical analysis. The recommended consequence assessment is based on the time to restore the system to its normal operation, and the areas affected by the attack, and the expected damage is based on attacker's and defender's capabilities.

Shin et al. [112] investigated resilience strategies against water CPS. Resilience is characterized in terms of four capabilities [112]: (i) ability to withstand disruption; (ii) absorptive capability (if disruption is unavoidable then minimize undesirable consequences; (iii) adaptive capability (adjusting to disrupted and undesirable conditions); (iv) restorative capability (recover quickly to completely normal operation). A resilience metric is proposed to measure the resilience of water systems against cyber-attack, and the C-town benchmark water distribution system is used as a case study to demonstrate the proposed metric.
