Flood susceptibility analysis of settlement basins on a provincial scale using inventory flood data

Settlements have been exposed to various disasters depending on their location and characteristics. One of these disasters is flooding, which affects the most widespread areas globally and causes significant economic loss. Numerous studies have been conducted at various scales, and different methods have been used to understand and mitigate the effects of floods. None of these studies conducted flood susceptibility analyses for settlement basins on a provincial scale using parameters derived from inventory basins. This study aims to determine the flood susceptibility of the settlements and their basins located along riversides and valley floors at the provincial scale based on the predominant morphometric characteristics of settlement basins that have previously experienced floods. For this purpose, a flood susceptibility analysis was conducted on 483 basins of 344 settlements located along riversides and valley floor morphologies out of 735 settlements in the province of Bursa (Türkiye). Among the morphometric and surface parameters frequently used in the literature, the nine parameters identified as having the highest impact for the 28 settlement basins in the training set—the bifurcation ratio ( \({\text{R}}_{\text{b}}\) ${\text{R}}_{\text{b}}$ ), drainage density ( \({\text{D}}_{\text{d}}\) ${\text{D}}_{\text{d}}$ ), time of concentration ( \({\text{T}}_{\text{c}}\) ${\text{T}}_{\text{c}}$ ), slope, topographic wetness index (TWI), stream power index (SPI), precipitation, hydrological soil groups (HSG), and lithology were applied to the other settlement basins. The results were validated with data from 22 settlement basins where flooding occurs, and maximum consistency was found. In the flood susceptibility analysis, the Normalised Morphometric Flood Index (NMFI) was used to evaluate each and overall parameters collectively. As a result, 51% of the settlements in Bursa province were identified as having high flood potential. This finding also reveals the prioritising of flood studies in three districts of Bursa province. This study identifies which settlements within the provincial border are susceptible to flooding and provides critical insights into which districts should be prioritised for flood risk management.