River and Coastal Flooding Hazard in the Vistula Outlet, Poland

Abstract

Flood risk at river-coast interfaces is an increasing concern under climate change and sea level rise, yet limited attention has been given to areas where riverine and coastal processes interact dynamically. This study assesses the river and coastal flood hazards in the Vistula River outlet, Poland, using multisource datasets handled via Geographical Information System (GIS) analysis. Flood hazard maps with return periods of 10, 100, and 500 years, which correspond to flood probabilities of 10%, 1%, and 0.2%, respectively, depending on the type of floods, were combined with detailed land cover and protected area datasets to quantify exposure to fluvial and coastal flooding. Results reveal that grassy vegetation and arable lands, covering more than two-thirds of the study area, are the most flood-prone land use categories, while built-up areas are particularly vulnerable in the event of levee breaches. Moreover, coastal flooding poses a greater threat than riverine flooding, both in extent and intensity, particularly affecting Natura 2000 sites located near the coast. These findings highlight the urgent need to integrate coastal and fluvial processes in hazard mapping and management frameworks in Poland, and to include compound flood considerations in national flood risk legislation. The approach presented here demonstrates the value of GIS-based assessments for identifying priority zones for flood mitigation, ecosystem conservation, and adaptive risk governance in deltaic and estuarine regions.