Hybrid Regional Flood Analysis in the Namak Lake Watershed

Regional Flood Frequency Analysis (RFFA) is an efficient method in flood discharge estimation in ungauged watersheds or with short-term statistics. The purpose of the present study is to evaluate the hybrid method in RFFA and maximum flood discharge estimation in the Namak Lake watershed, Iran. For this purpose, 16 hydrometric stations were selected. The selected hydrometric stations were then divided into five homogeneous areas based on watershed area. Three stations from different homogeneous regions were selected and used for validating the RFFA model, and with remaining 13 stations, the hybrid equations were estimated at 2, 5, 10, 25, 50, and 100-year return periods. The results showed that the accuracy of the RFFA models in the mentioned return periods are acceptable with the agreement index (d) more than 0.8. Root Mean Square Error (RMSE) in high return periods is also more than in low return periods. So that the lowest RMSE in the two-year return period was equal to 1.55 m3 s-1 and the highest in the 100-year return period was estimated at 14.64 m3 s-1.