Hydromorphometric Analysis of the Koya Basin in the Kurdistan Region of Iraq.

This study conducts a comprehensive hydromorphometric analysis of the Koya basin in the Kurdistan Region of Iraq, using ALOS PALSAR DEM data and GIS-based techniques to evaluate relief, linear, and areal parameters. The elongated basin (form factor = 0.21) features a sixth-order drainage network dominated by first-order streams, with high mean bifurcation ratios (Rb = 5.13) indicating structural control over drainage patterns. Moderate drainage density (1.95 km⁻¹) and infiltration number (4.31) reflect balanced dissection but elevated runoff potential, while rugged terrain (ruggedness number = 2.31) and significant relief (1,185 m) underscore topographic complexity. Comparative analysis reveals similarities to tectonically influenced basins in Erbil and Kirkuk, though Koya’s hypsometric integral (0.47) and dissection index (0.81) suggest a mature yet dynamically evolving landscape. Slope and aspect analyses identify southwest-facing slopes as hotspots for erosion and reduced soil moisture retention. The findings highlight the interplay between geomorphology and hydrology, emphasizing that elongated basin geometry mitigates flood intensity, while high-drainage-density zones necessitate targeted management. This study provides the first district-scale hydromorphometric assessment of the Koya basin, offering critical insights for policymakers to optimize watershed management, prioritize flood mitigation in structurally active regions, and enhance groundwater recharge strategies in semi-arid environments