The presence of water resources, particularly rivers, significantly influences site selection. Throughout history, settling near rivers has brought numerous advantages, but it has also posed certain risks. This study focuses on the sub-basins southeast of the Caspian Sea. Initially, we explore the connection between the layout of ancient Settlements and the drainage networks. Additionally, we analyze the relationship between flood risk and the Settlement patterns of these ancient sites by estimating the flooding risk based on linear, areal, and relief aspects. This research marks the first time such an analysis has been conducted. The findings underscore the importance of proximity to rivers in site selection, with areas close to rivers with lower stream orders being the most favorable for Settlements. The study reveals a decrease in the frequency of sites near higher stream orders in relation to flooding risk. Conversely, there is an increase in the frequency and density of ancient sites near the first stream orders and at greater distances from the rivers, coinciding with an elevated flooding risk in the sub-basins. These results indicate that the inhabitants of the southeastern areas of the Caspian Sea sub-basins were cognizant of the flooding danger and factored it into their decision-making when selecting Settlement sites