چكيده انگليسي :
Water is fluid that human beings noticed it’s vital importance more these days. Lock of management, improper use of groundwater, lack of water savings, and other factors have caused human beings to face with many water shortage problems and endanger the lives of many organisms. These day, man should be more concerned with preserving this valuable fluid. On the other hand, the production of greenhouse gases has caused us to face with many natural hazards, including: sudden floods and successive droughts. Lorestan province, especially Kashkan basin, is one of the flood-prone areas of Iran, which unfortunately has witnessed a lot of financial and human losses in recent years due to lack of proper management and lack of sufficient facilities to control sudden floods. In this research, it has been tried to evaluate the runoff amounts in three time periods, including short term (2022 to 2047), medium term (2048 to 2073) and long term (2074 to 2099) periods, each with different return periods of 2, 5, 10, 25, 50 and 100 years. Using these values, flood prone areas in the studied area (Kashkan Basin) will be identified through two management approaches including AHP and TOPSIS. To reach this purpose, this study examines the area in four stages. In the first stage, climate changes in precipitation, maximum and minimum temperature were investigated using CanESM2 model in three scenarios RCP2.6, RCP4.5 and RCP8.5 according to the fifth IPCC report for Khorramabad station with statistical period of 41 years (1965 to 2005). In the second stage, using SWAT and SWAT CUP softwares, an optimal model of the study area was produced. In the third stage, according to the future produced climatic data and the optimal model of the region, runoff risk was analyzed for the area in the time period of 2006 to 2100 with three 25-year intervals including short term (2023 to 2047), medium term (2049 to 2073) and long term (2075 to 2099) periods. In this study, the instantaneous peak flow was investigated using POT method and Easy Fit and FREQ softwares. In the fourth stage, sensitive areas of the region were identified using three zoning methods and two models including AHP and TOPSIS management approaches. Giving weight to parameters was performed using Expert Choice software. Finally, the flood risk zoning map was obtained with very low, low, medium, high and very high classification of risk levels. In addition, the annual peak flow thermal map for different sub-basins of the study area was projected in three short term, medium term and long term time periods using Python programming. In general, the results of this study showed that in the future (time period of 2006 to 2100), the maximum and minimum temperatures will be respectively between 1.3 to 3 Celsius degrees warmer and 1 to 2 Celsius degrees cooler than the base time period (1965 to 2005). The instantaneous peak flow will have a downward trend in the future due to climate change (decrease in precipitation and increase in temperature); this decrease of rainfall and flow should be compensated by using right management strategies. The study of instantaneous peak flow using POT method with return period of 2, 5, 10, 25, 50 and 100 years showed that the RCP8.5 scenario in the short term period with runoff calculation of 8995.94 cubic meters per second, the RCP2.6 scenario in the medium term with runoff calculation of 7715.44 cubic meters per second and RCP2.6 scenario in the long term period with runoff calculation of 4695.57 cubic meters per second are the lowest possible runoff mode which are likely to occur with a return period of 100 years. Instantaneous peak flow studies in different sub-basins showed that in the years of 2031, 2032, 2037, 2040, 2041, 2042, 2045, 2053, 2056, 2066, 2070, 2083, 2093, 2094, 2095, 2096, 2097, 2098 and 2099, there will be a possibility of runoff with intensities of more than 4000 cubic meters per second.
