Implementing spatial plans into modelling studies of flood risk in an Alpine region

Land provides essential ecosystem services to the people who, in turn, alter the land’s quantity and quality according to their needs (Verburg et al., 2015). Land-use change is therefore considered as a consequence of different human demands. However, increasingly conflicting land-use demands may cause challenges for land managers and planners. Among potential conflicts, economic development and natural hazard management require particular attention, particularly in combination with high population growth and environmental change (climate change: changing precipitation regimes; land change: increasing of the imperviousness, intensification of the agricultural production). This holds truth especially for the valley floors, where intensive socio-economic activity spatially overlaps with various hazard processes like flooding.

During the past decades, natural hazards such as floods have shown their potential to adversely affect economy and society in flood prone areas. Therefore, the public institutions (e.g., state agencies), the private sector (e.g., insurance companies) but also society as a whole have an interest in effective flood risk management. A region which was repeatedly affected by flooding in the past is the Federal Province of Vorarlberg, Austria, (2.601 km²; 388 711 inhabitants), where most of the settlements and industries are concentrated in the valley of the river Rhine (Schneeberger and Huttenlau, 2012).

We use Vorarlberg as an example, to show how the flood risk is considered in the past and future development plans. With a specific focus on flood risk areas, we evaluate the land usage in Vorarlberg since 2003 and identify how the land change and flood risk areas were considered in the spatial plans and development documents. For the assessments, we used the annually updated spatial plans from the period of 2003-2017 (RV) which identify areas allowing the future development (housing, industrial, administration units). Spatial plans were compared with the land change assessed by the annually updated cadastral maps (BEV).

Furthermore, considering the current trends and future projections of housing development, agricultural intensification and forest management, we construct future land change scenarios (up to 2050 and 2100) and identify the magnitude and areas of conflict between spatial planning, environmental protection and natural hazard. Our models show, for example, a much higher future housing demand as compared to demands considered in the spatial plans.

Relating to the flood risk, the agreement between the past and future plans and model output is relatively high for inundation areas with a return period of 30 years. However, several areas of current and future development are exposed to flooding with a return period of 100 years.
Our study confirms that innovative land change models and the spatially and temporally highly resolved data are crucial for considering the risk management in the current and future land man.