Flood Susceptibility Mapping in the İskenderun Gulf Basins (Türkiye) Using Morphometric and Multivariate Techniques

Floods, whose frequency and severity have increased due to both climate change and anthropogenic effects such as urbanization, deforestation, and land use changes, continue to pose serious risks to human life, infrastructure, and ecosystems worldwide. In regions like southern Türkiye, where complex topography, orographic precipitation, and rapid urban growth intersect, understanding flood dynamics is particularly critical. This study evaluates the flood susceptibility of 24 river basins that drain into the Gulf of İskenderun, focusing on the districts of Erzin, Dörtyol, İskenderun, Arsuz and Belen in Hatay Province. In this study, we developed a comprehensive framework for assessing spatial flood risk by integrating morphometric analysis with statistical classification methods. Fourteen morphometric parameters derived from 10-meter resolution digital elevation models were processed using GIS-based analyses. The proposed methodology involves two complementary analytical techniques: the Normalized Morphometric Flood Index (NMFI) and Principal Component Analysis (PCA). While the NMFI method enables a normalized (between 0 and 1) and weighted evaluation of flood susceptibility, PCA reduces data dimensionality and highlights the most influential morphometric factors contributing to flood potential. According to the results, a significant portion of the 24 river basins included in the study the moderate to high flood susceptibility categories. Moreover, PCA demonstrated superior performance compared to NMFI in terms of classification accuracy, recall rate, and overall reliability. Our analysis identified drainage density (Dd), bifurcation ratio (Rb), time of concentration (Tc), circularity ratio (Rc), and basin relief (Bh) as key parameters influencing flood potential. The strong agreement observed between the two methods suggests that morphometric analysis can serve as an effective tool for determining flood risk, particularly in basins where observational data is limited or flow gauging stations are absent. This research contributes not only to flood hazard and risk assessments but also to infrastructure planning and the development of disaster mitigation strategies. The proposed methodology can also be applied to other flood-prone areas with similar topographic and hydrological characteristics, thereby supporting sustainable watershed management.