Hydro-meteorological and impact characterization of floods in the Basque Country

Severe weather phenomena affect the Basque society in many ways, from disruption in various sectors and substantial damages in infrastructure to human and economic losses. Flooding is, among others, one of the natural event that causes a relatively high impact in Basque Country, usually as a consequence of intense and persistent precipitation.

In this study, we focus on the analysis of flood impacts produced in our territory and their meteorological characterization, during the period 1996-2021. The final objective is to contribute to knowledge of impact processes, increasing awareness and preparedness during flood events.

Impact from meteo-climatic hazards depend on the nature of the meteo-climatic severe event and on the vulnerability of exposed human assets to this particular hazard. In this work we use, as a proxy for flood impact, damages data paid by Spanish Insurance Compensation Consortium in the Basque territory during a twenty five years period (1996-2020). Such data are conveniently prepared with different aggregation level in order to facilitate its analysis at basin level and to draw conclusions. Results are presented grouped per date, period, amount, damage type, location and other relevant characteristics from each analyzed area in combination with some meteorological aspects.

A meteorological analysis of main impact events is performed using synoptic classification, and other weather types classifications (type of precipitation, cloud systems and severe weather categorization).Hydro-meteorological parameters are analyzed mainly based on data coming from the Basque mesonetwork and other data acquisition system available in the area (Radar, Meteosat, etc..). In the Basque Country, rivers flows in two main watersheds, the Cantabrian and the Mediterranean. In the Cantabrian basins high precipitations rates and steep slopes promotes river flooding with certain regularity in a relatively high populated and industrial area promoting more than 90% of total economic losses. The rivers of the Mediterranean side have less flood incidence due to lower precipitation rates, relatively softer slopes and less population densities causing less than 10% of total impact.