Document Type : Research Paper

Authors

• Masood Akbari ¹
• Parisa Mansouri ²

¹ Soil Conservation and Watershed Management Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

² M.Sc. Graduate of Hydraulic Structures, University of Zanjan

Abstract

The results reveal that the watersheds draining toward Abbar City possess considerable runoff generation potential and are capable of producing significant flood peaks under current land-use conditions, particularly for return periods between 50 and 200 years. Statistical analysis confirmed that the Gumbel distribution provides the most reliable estimates of extreme precipitation events, with a 200-year design rainfall depth of 71.7 mm. Simulation results obtained from HEC-HMS indicated that vegetation restoration through reductions in Curve Number values can substantially mitigate flood hazards. In the representative Sub-basin 6, peak discharge was reduced from 9.2 to 4.4 m³ s⁻¹, corresponding to nearly a 50% decrease. Furthermore, model validation based on six observed storm events yielded satisfactory performance metrics (R² ≈ 0.879, RMSE ≈ 0.208 m³ s⁻¹, and MAPE ≈ 4.23%), confirming the reliability of the model for reproducing flood hydrographs. Overall, the findings demonstrate that land-use management and enhancement of vegetative cover in upstream mountainous watersheds constitute effective nature-based and non-structural measures for attenuating flood peaks and improving flood resilience and hydraulic safety in Abbar City.

Keywords

• Flood Modeling
• HEC-HMS
• Vegetation Cover
• Watershed Management
• Peak Discharge Reduction