Topo-Hydrological Evaluation of Check Dams in the Al-Mujib Basin, Jordan

Abstract

In arid and semi-arid regions (ASARs), the effectiveness of rainwater harvesting (RWH) structures such as check dams is largely governed by terrain and hydrological dynamics. However, many existing structures are sited empirically, often neglecting systematic spatial evaluations. This study conducts a retrospective topo-hydrological assessment of 18 check dams in the Al-Mujib Basin, southern Jordan, to evaluate their siting efficiency. Five key indices Topographic Wetness Index (TWI), Stream Power Index (SPI), Topographic Position Index (TPI), Sediment Transport Index (STI), and Terrain Roughness Index (TRI) were derived from ASTER 30 m DEM and standardized to assess spatial suitability. The Receiver Operating Characteristic (ROC) curve and Area Under the Curve (AUC) metrics were employed to quantify the discriminatory power of each index. TPI and SPI demonstrated the highest predictive capacity (AUC = 0.850 and 0.822, respectively), confirming the significance of concave landforms and concentrated runoff zones an outcome that underscores the fact that most check dams were indeed located within geomorphologically favorable depressions and areas of high flow concentration. Composite suitability scores revealed that only 2 out of the 18 evaluated check dams (~11%) were classified within the high suitability category, while others exhibited suboptimal terrain–hydrology alignment. Correlation analysis indicated strong synergy between SPI and TWI (r = 0.94) and the statistical independence of TPI, reinforcing its unique value in capturing geomorphological depressions. This study highlights the critical need to validate dam placement through empirical spatial diagnostics, particularly in water-scarce landscapes increasingly vulnerable to climatic variability. The study underscores the significance of post-construction evaluations to monitor and maintain RWH structures for ensuring their efficacy and sustainability.