**4. Discussion**

This research investigated land use in flood-prone areas to assess the pressure these areas are undergoing and the resulting consequences.

In the case study area, the space for river channels has been reduced by 40% since the middle of the 19th century. In addition, research shows a strong reduction in wetlands there [35]. This significant reduction was caused by river straightening and drainage works in order to decrease the impacts of frequent flood events and to reclaim wetlands for development and intensified agriculture. In the long run, however, these measures led to an increase in flood hazard due to the decreasing space for runoff in the case of floods with low and medium probability [23]. Furthermore, the reduction in glaciers impacts flood runoff. These past developments underline the importance of policies for making space for rivers, not only to reduce flood risks but also to improve the ecological situation of riverine landscapes.

In the case study area, settlement development between the middle of the 19th century and 2016 took place inside and outside flood-prone areas; however, the relative growth is significantly higher inside flooding zones. This result shows a shift towards the use of flood-prone areas for settlement development, which depicts an increase in flood damage potential. This rise in damage potential can also be observed in other exposure-related studies [5,27–29,47]. A multi-hazard exposure analysis for Austria shows a general increase in buildings by 643% between 1919 and 2012, properties exposed to river flooding have grown by 650%, and buildings exposed to torrential flooding have risen by 594% [29]. A general increase in flood damage potential due to settlement development can therefore be observed throughout the scientific literature.

Besides settlement development, our research results also point out that the share of settlements affected by flooding is higher in mountainous regions. In Alpine regions, the space for permanent settlement is limited and, due to the topography, is mainly located in the valleys. At the same time, flooding zones cover big parts of the valley floor. Therefore, there is an overlapping of flood-prone areas and the area for permanent settlement. Land use pressure on flood-prone areas is not limited to Alpine regions in Austria; other mountain areas face similar challenges of settlement expansion and decreasing space for flood runoff [48].

When it comes to the demand of making space for rivers, agricultural areas are the first choice. They provide areas for infiltration and runoff, with potential flood damages being on a lower level compared to settlement areas. The results show that agricultural land is decreasing, with Alpine regions showing a greater decline. In addition, the percentage of agricultural land within flood-prone areas is higher in mountain areas than outside. To gain a better understanding of the impact of flooding on agricultural land, a differentiation between agricultural areas with different characteristics is necessary. According to Grüneis et al. [30], the flooding of agricultural land results in quantifiable economic losses for farmers such as crop damages, erosion, landfall silting, and contamination, as well as hardly quantifiable environmental damages. These economic losses depend on crop species, growth stage, and soil properties and affect not only single-farm enterprises but the whole agricultural sector. This leads to macroeconomic questions of saving regional food supply, which has recently gained more importance, especially due to the increasing land-take by settlements and thus decreasing agricultural land. The results show that, at a national scale, the percentage of highly valuable agricultural land in flood-prone areas is higher in Alpine regions. This is also underlined by regional results. The western part of Carinthia is more mountainous (which is reflected in the limited space for permanent settlement—see Figure A3 in Appendix A) and also displays a higher amount of valuable farmland in flood-prone areas than the eastern part.

In the example of Carinthia, our results show that the share of settlements and valuable agricultural land in flood-prone areas is higher in pronounced mountain regions. The overlapping of flood-prone areas, valuable agricultural land, and settlements is likely to reduce the options of providing land for flood risk managemen<sup>t</sup> and river restoration.

Research on the current use of former floodplains in Austria in 2003 concludes that over half of them are nowadays used for field crops and grassland [49]. The use of former floodplains for agriculture contributes to the fact that valuable agricultural land is nowadays located in flood-prone areas. The higher amount of valuable agricultural land in flood-prone areas in Alpine regions is further explained by a higher soil quality in the valley areas and the topography, which limits the use of space for agricultural production.

Research by Haidvogl et al. [50] in the area of St. Pölten in Lower Austria discusses the interdependencies of flood protection measures and settlement development. In combination with population growth, the demand for building land, and the construction of flood protection measures, settlement development along the river Traisen in 'flood-protected' areas was encouraged [50]. However, there remains a residual flood risk after the construction of flood protection measures [51]. The so-called 'levee-effect' or 'safe-development paradox' describes an increasing flood damage potential in areas with residual risk [52,53]. This research did not specifically focus on areas with residual risk behind levees due to the scale of the analysis. However, these areas are included because of the extent of the flooding areas applied. The increasing settlement development in flood-prone areas can therefore be connected to the construction of flood protection measures and the creation of 'flood-protected' areas. Besides the 'levee-effect', the limited space for permanent settlement in Alpine areas and the general increase in settlements led to an increase in flood damage potential.

Based on the results, consequences for flood risk managemen<sup>t</sup> can be derived. Making space for rivers to reduce future flood damage is an important approach that is confronted with limited space and land use pressure in Alpine regions. Many former floodplains, which nowadays could be used for river restoration, e.g., local widening of watercourses or reconnecting rivers with previous river branches, were often claimed by settlement and agriculture. In other countries, the approach of making space for rivers also faces difficulties [19,20,24]. In general, research suggests that a broad inclusion of relevant stakeholders

at different governmental levels is necessary to implement a flood risk managemen<sup>t</sup> that aims to make more room for rivers [16,19]. One of these disciplines is spatial planning, which takes on an important role when it comes to keeping flood runoff and retention areas undeveloped. Another important stakeholder is agriculture. As a major land use agent, it influences the emergence of floods. Agricultural cultivation substantially contributes to flood risk reduction. Reducing surface runoff and maintaining the infiltration capacity of the soil are particularly effective, as developing land for the purpose of retention can additionally reduce floods [43,54]. In general, integrated flood risk managemen<sup>t</sup> is an interdisciplinary approach including a broad range of technical and non-technical measures to reduce flood risks, in addition to giving space to rivers. This includes emergency measures, flood-adapted building, and hazard zone mapping [12].

The limitations of making room for river are not only connected to the lack of space; the implementation also needs a general shift towards an integrated flood risk management, including a wider range of stakeholders.
