ارزیابی خطر سیل و عوامل مؤثر بر آن در حوضه آبخیز زهر-جراحی در جنوب غرب ایران با استفاده از روش سلسله‌مراتبی فازی

ABSTRACT
Iran has experienced many extreme flood events in the last century. The necessity of creating prediction and zoning systems in most of the watersheds of this country has been given more attention than ever before. The purpose of the study focused on flood risk mapping and the risk index assessment based on the GIS-FAHP-multi-criteria decision-making process. Thirteen risk-relevant variables, including both quantitative (such as precipitation, elevation, slope, plan curvature, NDVI, distance from the river, drainage density, SPI, TWI, and CN) and qualitative factors (such as land use, landform, and geology). The raster maps of the investigated variables were prepared using ESRI ArcGIS software. The fuzzy overlay function (AND, OR AND GAMMA) has been applied after each layer for fuzzification with proper fuzzy function in ArcGIS10.8. The result of different fuzzy operations indicates that gamma 0.9 showed more accuracy when compared to the flood events than other fuzzy overlapping operators in the region. The resulting map showed that mountain areas and areas with high slopes in the north and northwest of the study area were very susceptible to flooding and were classified in the high flash flood susceptibility class.
Extended Abstract
Introduction
Floods are the most frequent type of natural disaster and occur when an overflow of water submerges land that is usually dry. Floods have the most significant damage potential of all-natural disasters worldwide and affect the greatest number of people. Flood risk management has proven successful at reducing the threat of some flooding in order to reduce and control these damages. A flood can occur when water enters the watershed too quickly for the land to absorb; on the other hand, a flood is the maximum water flow of a watershed. Extreme flooding events are not relegated to the least developed nations but can devastate and ravage the most economically advanced and industrialized nations. Floods harmfully affected crops and their production in many areas of the world. Flooding and heavy rain have caused problems for people across parts of Iran. Our study area is located southwest of Iran and has been affected by several flood events in recent decades. This area has a complex topography, dry climate, and poor vegetation that causes it to be more susceptible to flood risk. One Keelung city of Taiwan research study applied a geographic information system (GIS) and artificial neural network (GANN) model for flood susceptibility assessment. Various factors were used, including elevation, slope angle, slope aspect, flow accumulation, flow direction, topographic wetness index (TWI), drainage density, rainfall, and normalized difference vegetation index. The results show that nearly 3.5% of the study area, including the core district of the city and an exceedingly populated area, including the city's financial center, can be categorized as high to very high flood susceptibility zones. This article aims to analyze flood risk and influencing factors in the Zohr-Jarhari Basin in the Southwest of Iran using the Fuzzy analytic hierarchy process (FAHP) approach.
 
Methodology
The Zohr-Jarhari Basin (Southwest of Iran) is very susceptible to floods. This catchment drains into the Persian Gulf and was selected as a study area because of its high population density and resulting exposition to hazards. This region is situated in the southwest of Iran, ranging from 48°16′ to 52°16′ N and 29°46′ to 31°40′ E, and covers an approximate area of 41.014 km². The area is located at the interface between the over-thrust and the folded Zagros, following the over-thrust Zagros structurally. The altitude of the area varies from 0 to 3639 m a.s.l., with the Zohreh-Jarahi catchment comprising 24 sub-catchments. Although most of the sub-catchments are located in Khuze stan province in southwest Iran, some parts of the study area are also found in Fars, Kohgiluyeh, and Boyer-Ahmad provinces. Therefore, the present study focused on flood risk mapping and the risk index assessment based on the GIS-FAHP-multi-criteria decision-making process. Thirteen risk-relevant variables, including both quantitative (such as precipitation, elevation, slope, plan curvature, NDVI, distance from the river, drainage density, SPI, TWI, and CN) and qualitative factors (such as land use, landform, and geology). The raster maps of the investigated variables were prepared using ESRI ArcGIS software. The fuzzy overlay function (AND, OR AND GAMMA) has been applied after each layer for fuzzification with proper fuzzy function in ArcGIS10.8.
 
Results and Discussion
This study created Flash flood susceptibility maps using the effective factors in flood susceptibility and the FAHP (Fuzzification and Criteria Weights (%)) algorithms. After weighting the criteria and sub-criteria examined in the research in order to zone the flood potential in the watershed, the sub-criteria layers of the research using fuzzy operators Gamma 0.5, Gamma 0.7, Gamma 0.5, AND, Sum Algebra (OR) have been used. The result of different fuzzy operations indicates that gamma 0.9 showed more accuracy when compared to the flood events than other fuzzy overlapping operators in the region. The resulting map showed that mountain areas and areas with high slopes in the north and northwest of the study area were very susceptible to flooding and were classified in the high flash flood susceptibility class. The analysis of the final weights of the FAHP shows that the Stream Power Index variables with correlation coefficient, NDVI, rainfall and geology have the greatest impact on the flood potential in the study area.
 
Conclusion
Meanwhile, the use of modern technologies and new methods of water resources management and a better understanding of the climatic condition of the region can improve the situation for the society and the environment. This study combined Fuzzy and AHP algorithms to create a flash flood susceptibility map using flash flood conditioning factors. The study shows the important role of GIS in the decision-making process. The maps in the current study indicated that mountain heights in the east and southeast of the basin are vulnerable to flooding and must be a preference for management to stop alleviating flash flooding. These flash flood susceptibility maps could be used to reduce the future harm made by flash floods, to help the disaster management processes in the future, to improve greater methods for preservation, to extend the research, and to develop flash flood predictions and precaution systems. Meanwhile, the use of modern technologies and new methods of water resources management and a better understanding of the climatic condition of the region can improve the situation for the society and the environment.
 
Funding
 There is no funding support.
 
Authors’ Contribution
 All of the authors approved thecontent of the manuscript and agreed on all aspects of the work.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.