Changes in Flood Hydrograph Components Due to Long-term Land Use Changes in Ardabil Nenakaran Watershed

Flood as a natural hazard is under the control of many dynamic factors, and its occurrence is strongly controlled by land use attributes. The type of land use and its dynamic changes is considered as the most important factor in runoff generation. Therefore, the purpose of this study is to assess the impacts of land use changes on flood hydrograph components in a partially forested watershed in Ardabil province. The rate and extent of land use change has been quantified during 1993, 2000, 2010, and 2020 years. In the present study, Landsat time series satellite images, ENVI 5.3 and Google Earth software were used to classification of the land use maps. The flood hydrographs of the study area were simulated using Wildcat 5 software under the design rainfall amount in the 25-year return period. The results land use changes assessment showed that the extent of forest lands has decreased by 20% and rangelands by 4%. Also, agricultural lands increased by 20% and the increase of barren and residential lands were 3% and 1%, respectively. According to the results, the most land use changes were in the western and southern parts of the basin having lower altitude and lower steepness. In addition, according to the results of flow simulation, the maximum peak flow was 34.46 cubic meters per second in 2010 compared to the base period (year 1993). As a conclusion, the results showed an increase in surface runoff and a decrease in the time to peak component of the design hydrograph in the study period.