A new approach to flood susceptibility analysis of urbanised alluvial fans: the case of Bursa City (Türkiye)

Abstract

Floods stand out as one of the most significant disasters impacting human life, causing widespread economic and social damage across the globe. Numerous research studies have concentrated on comprehending the contributing factors of flooding. Despite the prevalence of morphometry-based basin flood susceptibility analyses in existing literature, a comprehensive examination that encompasses anthropogenic features in alluvial fans is notably lacking. This study aims to evaluate the flood susceptibility of alluvial fans and their catchments in urbanised areas, integrating individual and collective basin/fan (B/F) morphometry and land use characteristics with flood inventory data. The study area selected for this investigation is the basin and fan systems situated on the northern slope of the Uludağ Massif (2543 m), the highest point in the Marmara Region, northwestern Türkiye. Twelve basin morphometric parameters were applied to 5 m resolution Digital Elevation Model data, while six fan morphometric and anthropogenic parameters were applied to alluvial fans. In addition, the results were assessed using the Normalised Morphometric Flood Index method to mitigate subjectivity in result ranking. According to the integrated basin/fan flood susceptibility results obtained through bivariate analysis, B/F6 exhibits a very high susceptibility, while B/F1, B/F3, B/F2, B/F5, B/F4, and B11/F8 demonstrate high susceptibility. B7, 8, 9, 10/F7 display a moderate potential for generating floods. These findings align significantly with historical flood events in the basin/fan area.