The Sendai Framework for Disaster Risk Reduction 2015-2030 states that the implementation of effective disaster risk reduction measures should be based on an understanding of disaster risks, including all aspects of vulnerability, capacity, exposure of persons and hazard characteristics. Understanding these disaster risks establishes the basis for the development of impact models and impact-based warnings.
In recent years there has been increasing interest in multi-hazard impact-based warning systems to reduce the impact of natural disasters. For example, in 2015 the World Meteorological Organisation (WMO) published ‘WMO Guidelines on Multi-hazard Impact-based Forecast and Warning Services’ for National Meteorological and Hydrological Services and their partner agencies responsible for issuing warnings. Impact-based warnings use a combination of likelihood and potential impact to assess the risk of a hazard event and therefore which warning to issue. The whole decision chain from assessing the likelihood of a hazard and potential impacts to deciding which warning severity to issue to warning communication and verification is complex. For many hydrometeorological events the likelihood can be assessed by using ensemble prediction systems, but an assessment of impacts is often highly subjective. To aid the decision making process hazard impact models and methods for multi-hazard assessment have been developed. These are at the cutting-edge area of research and require a multi-disciplinary partnership approach. This research not only spans hydrometeorology but all natural hazards ensuring that people receive the best advice and information to build their resilience and prepare for natural hazard events.

This session invites presentations from all natural hazard areas on:
• Impact based warning systems that are being developed or have been implemented across the world
• The decision making process of meteorologists and other hazard specialists in issuing warnings
• Research and development of explicit hazard impact models and multi-hazard systems
• How impact models are used to aid the decision making process
• Verification of impacts and collection of impact data
• Communication of this information to governments, civil contingencies, the responder community and the public.