Linkage of geographically weighted regression with spatial cluster analyses for regionalization of flood peak discharges drivers: Case studies across Iran

Iran has experienced very destructive flooding events with significant socio-economic and environmental consequences over the last years. Identifying and analyzing the driving factors of flood peak discharges (FPDs) with different return periods in the Iran's basins provides a clear picture of the impact degree of different factors on the flood which is crucial for proper management of flood and associated risk mitigation. In this study, the longterm (>30 yr) data of 206 continuous-gauging stations across Iran with various hydro-climatic characteristics were selected for the spatial analysis of FPDs drivers with an average recurrence of 2- to 1000-yr. For this aim, the change points, trend analysis, stepwise regressions, global and local Moran's I index, geographically weighted regression (GWR) and two-step cluster analysis were utilized. The results of GWR model demonstrated the drainage area, elevation, heavy precipitation, slope and NDVI are the most FPDs drivers in different frequencies (Q2 to Q1000). The regression coefficients indicated an increase in FPDs with increasing drainage area, heavy precipitation and slope while a decrease in FPDs magnitude obtained with increasing elevation and NDVI for all study basins and different frequencies (Q2 to Q1000). The results also showed that the impact degree of vegetation increases from Q50 to Q1000 and heavy precipitation from Q100 to Q1000. The findings of this study and the proposed methodology provide a replicable research practice that can help the managers and decisionmakers to adopt/implement policies for flood risk management.

Automated summary

This study analyzed the driving factors of flood peak discharges in Iran's basins using GIS, showing that drainage area, elevation, precipitation, slope, and NDVI are the main drivers of flood peaks at different frequencies. The results suggest that flood peak discharges increase with drainage area, heavy precipitation, and slope, while decreasing with elevation and NDVI across all study basins and frequencies.