Multi-hazard risk and the asynergies of disaster risk reduction measures: the need for an integrated approach

Many countries face the risk of multiple hazards. Nonetheless, most Disaster Risk Reduction (DRR) measures are aimed at one hazard type. However, while positively influencing the risk of one hazard, DRR measures can have adverse effects on the risk of another hazard type. Most research on hydrological risks focuses either on flood risk or drought risk, whilst floods and droughts are two extremes of the same hydrological cycle. To better design disaster risk reduction (DRR) measures and strategies, it is important to consider interactions between these closely linked phenomena. We show examples of: (a) how flood or drought DRR measures can have (unintended) positive or negative impacts on risk of the opposite hazard; and (b) how flood or drought DRR measures can be negatively impacted by the opposite hazard. In a case study of Afghanistan, we calculate the asynergies of structural, building-level DRR measures for floods and earthquakes using two scenarios where DRR measured are aimed at either decreasing flood or earthquake risk. These scenarios are used to assess the asynergies and to illustrate to what degree a reduction of one risk may actually be offset by an increase in the other hazards risk. This is then used to show which type of measure is worthwhile in which part of the country. Overall we find that an improved capability of understanding risk and interactions between disaster risk reduction measures more comprehensively would strongly benefit first responders, aid organizations, urban planners and decision makers in designing sustainable DRR measures.