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

This paper presents a community-centred framework named ‘site-specific early warning system’ (SS-EWS) to co-design and co-evaluate with communities an impact-based warnings (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.

Findings from the study show that the evaluation of the SS-EWS for 2020–2021 had promising results in triggering SSW levels, using point and basin-aggregated rainfall forecasts, compatible with the reported impacts and proposing appropriate protection actions to reduce the local risk dynamically. By implementing site-specific thresholds within a community, rather than the regional thresholds used officially by the SMC, IBEWS can enable end-users to make local actionable decisions at sites with different vulnerability profiles.