# Flash Floods Hazard to the Settlement Network versus Land Use Planning (Lublin Upland, East Poland)
## 1 Introduction
The threat of such phenomena is on the rise, and at the same time the number of new buildings is also increasing. It is emphasized that the rational use of land is a very good way for humans to adapt to projected climate change [44; 45]. At the same time, it should be emphasized that the lack of permanent drainage and locations other than the bottoms of river valleys can mean that investors and local authorities are unaware of the threat to development posed by flash floods. It is difficult to determine precisely the scale of the threat of flash floods in Poland. A flash flood is a short-lived local phenomenon that is not usually recorded by hydrological monitoring systems. The primary source of information is publications describing their hydrological and geomorphological effects. For the period 1932-2009 for the entire area of Poland, [PERSON] [10] was able to identify 108 flash floods described in publications. In turn, [PERSON] et al. [14] found that in the Lublin Upland area in the second half of the twentieth century, there were approximately 40 heavy rainfall incidents which led to flash floods. The true number of flash flood events is certainly greater. According to Polish Fire Department data, 20,000-30,000 interventions in connection with excessive rainfall and flooding are registered annually in Poland [46]. Of course, not all of these phenomena can be considered flash floods. However, according to insurance companies, in June 2020 in Poland, affected residents reported more than 50,000 cases of damage related to flash floods [47]. Our study fills the research gap concerning a lack of connection between the results of environmental (hydrological) studies and land use planning practice. The research published to date has been primarily in the nature of hydrological studies (detailed assessment of the degree of threat of flash floods) without taking into account the existing planning reality. This study had the following specific objectives: (a) identification of catchment areas with buildings located on episodic surface runoff lines; (b) assessment of the number of buildings potentially threatened in catchments with a big share of arable land; (c) assessment of the susceptibility of these catchments to flash floods; (d) for the most susceptible catchments, determining whether this threat is present in the planning documents for these areas. In our study, we tested the following research hypothesis: in areas with high susceptibility to flash floods, this threat is present in planning documents. This study was undertaken in selected rural municipalities of Lublin. Buildings located in areas threatened by potential dynamic runoff and flash floods were identified in first-order catchments without permanent drainage. Due to the lack of sufficient data on real flash flood events, it was not possible to develop models to assess the probability of their occurrence. While the intensity of this threat was not specified, areas with favorable episodic surface runoff formation were identified. A simple susceptibility assessment based on publicly available data was conducted, as this did not require a database of past meteorological and hydrological events. Simple qualitative assessment of the catchment's susceptibility to flash floods was made on the basis of commonly applied criteria. This method can be applied by anyone preparing planning documents with a basic knowledge of GIS. The extent to which this problem is present in documents related to local land use planning for these catchments was then analyzed. This type of detailed assessment has not been undertaken before in Poland. Studies that have been conducted have focused primarily on permanently drained and somewhat larger catchments [48; 49]. Identification of sites and areas threatened by flash floods allows the determination of detailed development rules to reduce the effects of the phenomenon not only within the parcels with buildings but also on the type of land cover and changes in the functional and spatial structure.