Design and evaluation of a community and impact-based site-specific early warning system (SS-EWS): The SS-EWS framework

The recent extreme rainfall events in Spain such as the storm Gloria have highlighted the gaps in emergency communication, particularly the disconnect between the available impact-based early warning systems (IBEWSs) and the steps communities take during emergencies. This paper presents a community-centred framework named ‘site-specific early warning system’ (SS-EWS) to co-design and co-evaluate with communities an IBEWS for vulnerable locations within high-risk areas. The components of the framework guide communities in identifying and evaluating local impacts; establishing impact and advisory tables; deriving impact-based rainfall thresholds and warning levels; and configuring the SS-EWS with radar-based nowcasting and numerical weather prediction (NWP) models. A first implementation and evaluation of the SS-EWS have been done for a public school, two ford crossings and the city of Terrassa, Spain. The SS-EWS shows promising results in triggering location-based or site-specific warnings compatible with the reported impacts and proposing actions to reduce the local risk. Furthermore, the combination of NWP and radar-based nowcasting improved the capacity of the SS-EWS to monitor the evolution of the precipitation and capture highly intense rainfall. The SS-EWS can be a straightforward and cost-efficient complement for regional EWS to increase the preparedness of communities.