Flood Risk Analysis in the Area of Allotment Gardens in Poland: Example of the Voivodeships: Silesia, Opole and Lower Silesia

Allotment gardens (AG) provide a unique combination of urban and suburban productive and recreational spaces with numerous functions. As part of ecological systems, they are experiencing a renaissance, driven by contributions to fostering more sustainable cities. Unfortunately, hydro-hazards are increasing in frequency due to climate change, often because of the specific location of allotment gardens in low-lying areas and river valleys. The article aims to analyze flood risk to AG in the area of three voivodeships in south-western Poland: Lower Silesia, Opole, and Silesia. The analyzed AG, having diverse landscapes and hydrographically belonging to the Odra River Basin, are frequently affected by catastrophic floods. The objective of the study is to create flood risk maps separately for each area at risk of flooding with a probability of 0.2%, 1%, and 10%, taking into account the land use of individual allotment gardens. For this purpose, the building coverage ratio (BCR) was used in the study, which required the acquisition and processing of LiDAR data. One of the most important findings is that the building coverage ratio (BCR) does not differ significantly between allotment gardens located in and outside flood-prone zones. This result suggests that flood risk was not a major factor influencing the density of development in the analyzed allotment gardens. The spatial analysis also revealed that a considerable number of allotment gardens are located within the officially mapped flood hazard zones, with nearly 10% of the analyzed AG situated within the 0.2% annual exceedance probability zone. Moreover, observations from the 2024 flood event indicate that local inundation may also occur outside the areas identified by the available flood hazard maps, highlighting the uncertainty associated with modeling the spatial extent of individual flood events.