Risk-based flood zoning employing expected annual damages: the Chenab River case study

Flooding proves to be the most devastating and annihilating natural hazard in Pakistan. Existing flood management strategies are riveted primarily to the structural measures that contribute limited loss reduction capability at the national level. Non-structural measures are not part of regular practices, as the adopted design standards, which are probabilistic in nature, are unable to assess their feasibilities. An improved risk-based assessment using expected annual damages (EAD) is introduced in this article for the evaluation of combined impacts. EAD treat the probabilistic nature of losses and provide an extended visualization of risk distributions in the form of damage curves and expected annual damages distribution maps. The Chenab River floodplain was selected to study the coalesced response of embankments and flood zoning, preliminary in economic terms. In this regard, the impacts of all likely floods are considered instead of the traditional focus on a single design flood. Damage curves and maps are compiled using estimated losses and probabilities of all floods. Flood zoning for agricultural land is performed. The results support choosing a multidirectional conjunctive approach that considers multiple measures to reduce flood losses. These results can be used as a vital input for the decision-making process.