Identification and Analysis of the Dominant Factors Contributing in Intensification of Floods and Damages in the Karkheh Basin in April 2018

Human interventions, including land-use change and encroachment on river boundaries along with the impacts of the climate change have resulted in an increase in flood damages. This study aimed to identify and analyze the factors intensifying the floods of April 2019 in the Khuzestan province. To this end, we determined the return period of large floods in the region in April 2019; investigated land-use changes between 2000 and 2018 by using the random forest classifier; explored the changes in the soil moisture using remote sensing data; and analyzed the rule curve of the Karkheh and Dez dams. The results showed that the discharge observed at the Jelogir station, as the nearest station upstream of Karkheh Dam had a return period of 262 years, which is far greater than the return period of historical floods in the study area. The weak correlation between runoff intensity and antecedent soil moisture at 5% confidence level during 30, 45, 60 and 120 days before the flood indicated that beside the antecedent soil moisture other factors such as rainfall intensity and snowmelt were contributing to the intensified flood. We further concluded that the change in the land-use between 2000 and 2018 in the study area cannot be considered as a strong factor in the intensification of floods. Finally, the operation of Dez Dam in the water year of 2018-2019 had a much more effectiver impact on the flood control of April 2019 compared to the operation of Karkheh Dam.