Multi-Dam Failure Propagation in a Transboundary River System: A Case Study of Azad–Daryan–Hirwa–Darbandikhan Cascade
Volume 12 , Issue 1 , December 2025 , Pages 24-42
Authors
Fryad Hama Ibrahim 1 ; Kawa Zaidan Abdulrahman 2
1 Department of Water Resources Engineering, College of Engineering, University of Sulaimani
2 Department of Water Resources Engineering, College of Engineering, University of Sulaimani
10.17656/sjes.102000
Keywords
Abstract
This study investigates the hydrodynamic consequences of cascading dam failures within a transboundary reservoir network involving the Azad, Daryan, and Hirwa dams in western Iran, and their downstream impact on the Darbandikhan Dam in northeastern Iraq. Using HEC-RAS 6.6 2D modeling, four breach scenarios were developed, with two key cases sequential overtopping and mixed-mode failure analyzed in detail. Simulations revealed that Scenario 1, involving full-capacity overtopping, poses the highest risk, with flood waves propagating rapidly through narrow valleys and causing peak water surface elevations of 512.0 m at the Iran–Iraq border and 493.2 m near Darbandikhan Dam, overtopping the spillway gates set at 485.0 m. Over 1,000 houses between Azad, Daryan and Hirwa dams are projected to be submerged, and Hirwa Village is completely inundated under flood depths exceeding 22 meters. Downstream in Iraq, at least 12 villages inundated under flood depths exceeding 2.5 and more than 70 km² of agricultural land are affected, including major infrastructure such as the Halabja highway, submerged under over 2 meters of floodwater. Flow velocities ranging from (10 to 25 m/s) exceed sediment entrainment thresholds, indicating substantial erosion, sediment transport, and long-term morphological impacts on reservoir banks and channels. The findings underscore the urgent need for structural improvements, dynamic reservoir operation protocols, real-time monitoring, and cross-border emergency coordination. The study also highlights the importance of incorporating geomorphic and climatic factors into future dam safety strategies.