Estimation of flood in the catchment area of reservoir dams using a multi-criteria decision-making system (Case study of Kermanshah Province)

Undoubtedly, floods can be considered as one of the most effective natural hazards that cause many human and financial losses every year. A flood is defined as an overflow of water or its overflow in a river or spring, which is a threat to the life and property of residents near these sources. In simpler terms, any relatively high flow that impinges on natural or artificial banks in any direction of a stream is called a flood.  In this research, the effective criteria related to the estimation of flood design discharge in reservoir dams in 17 in Kermanshah province were identified and prioritized, and then in order to review and analyze the effective factors in estimating the flood estimation separately for each reservoir dam, were evaluated using 8 different multivariate decision-making methods.  Considering the large number of studied dams the four hydrological agents and comprehensive options such as design flood estimation in connection with the occurrence of hydrological events in the area by human origin, with natural origin, the quantity and quality of information and hydrometeorological data and the limitations of methods (statistical, experimental, models) were selected and prioritized with SAW, AHP, FAHP, VIKOR, TOPSIS, FTOPSIS, PROMETEE, Electre III methods. Based on the mentioned 8 methods, 22 criteria involved in estimating the flood yield of 17 reservoir dams were ranked.  In the SAW method, experimental methods with 6 rank 1, statistical methods with 5 rank 1 and physiographic parameters with 2 rank 1 are the most important effective criteria in estimating the flood entering the reservoirs of dams studied in this research. In the AHP method, hydrometric stations and the true limit of the basin were the most important effective criteria with 5 and 3 ranks, respectively. In the FAHP method, experimental methods with 6 and statistical methods with 5 ranks were recognized as two important criteria. In TOPSIS method, statistical methods, physiographic parameters and conversion of maximum flow to maximum instantaneous flow rate each with 1 first rank, and Fuzzy TOPSIS experimental methods, statistical methods and conversion of maximum flow rate to instantaneous flow rate with 6, 4 and 2 first rank respectively. In ViKor's method, only experimental methods have 1 rank. In the Electra method, the criteria of meteorological stations, the true limit of the watershed and experimental methods were evaluated as effective criteria with 1 rank. Finally, in the PROMETHEE method, only the experimental method with one item was ranked 1 rank.  The results showed that more than 76% of the dams have priority in the option of conditions and limitations of flood estimation methods (statistical, experimental, model, etc.) and 24% have problems in the option of quantity and quality and water and meteorological information.. The option that has more frequency than other option of the conditions and limitations of the flood estimation method (V4) of each reservoir dam. Based on the review of documents and documents of flood analysis and achieving the design flood in the studies of the first and second stages of reservoir dams of the studied dams, this conclusion is confirmed, in the statistical methods, the length of the statistical period is low and the frequency distribution function is not recognized properly. In addition, the use of experimental methods, which are mainly applied without recalibration of relevant coefficients and without necessary precautions and checks, is one of the weaknesses of flood estimation.