تحليل فضايي مخاطرات ژئومورفيك تهديد كننده مجتمع هاي زيستي شهري در استان لرستان

Geomorphological hazards threatening the spatial analysis of urban living complex in Lorestan province

انسان از ابتداي حيات خود دائما با تهديد هاي ژئومورفيك مواجه بوده و اين مخاطرات، خسارات جاني و مالي را در زيستگاههاي انساني و به ويژه در شهر ها براي جوامع انساني به دنبال داشته است. امروزه شهرها در نقاط مختلف دنيا به دلايل متعدد در معرض آسيب ناشي از مخاطرات ژئومورفيك قرار دارند، كه شهرهاي استان لرستان واقع در رشته كوههاي زاگرس نيز از اين قضيه مستثني نيستند. هدف از اين تحقيق پهنه بندي و شناسايي پهنه هاي پرخطر ژئومورفيك در مناطق شهري استان لرستان با استفاده از روش توصيفي- تحليل و تجربي مي باشد. در روش توصيفي داده ها و اطلاعات مورد نياز از منابع و سازمانهاي مختلف تهيه شد. در روش تحليلي عوامل موثر در پهنه بندي مخاطرات ژئومورفيك زلزله، سيل، زمين لغزش و روانگرايي و تلفيق آنها جهت تهيه نقشه مخاطرات ژئومورفيك با استفاده از تحليل هاي مكاني GIS و مدل هاي AHP و منطق فازي انجام گرفت. ابتدا پارامترهاي موثر در رخداد هر يك از مخاطرات شناسايي و پس از استانداردسازي پارامترها با استفاده از توابع كاهشي و افزايشي منطق فازي و وزن دهي به پارامترها با استفاده از تحليل سلسله مراتبي، پهنه هاي پرخطر در شهرها شناسايي شد. نتايج نشان داد كه اكثر شهرهاي استان لرستان به دليل عبور رودخانه هاي اصلي از محدوده شهرها، در معرض خطر سيلاب قرار دارند. هم چنين مشخص شد كه شهرهاي واقع در غرب استان در معرض خطر سيلاب و شهرهاي شرق استان در معرض خطر زلزله و رخدادهاي ژئومورفيك ناشي از زلزله مانند زمين لغزش و روانگرايي قرار دارند.

Natural hazards are basically the changes that occur in environmental conditions، causing a disruption of the natural life of the people and their exposure to hazardous and degradable elements and elements. Establishing cities and residential areas on landforms has created new perspectives. The development of these areas has altered the geostationary balance of many landforms، and the response of geosystems is an expression of geomorphological hazards such as land subsidence، fault activity، flood، and the like that threatens residents of urban areas. The trend of population growth in the urban areas of Lorestan province in western Iran has also caused the physical expansion of the provincial cities in the periphery. This development has resulted in landslides and areas that، in many cases، have not been studied in environmental and environmental sustainability. The consequence of this is to increase the risk factor of these areas against a variety of hazards. In this regard، the aim of this study is to analyze the geomorphic hazards of earthquake، flood، landslide and liquefaction in the 9 major cities of the province and zonation of areas based on the degree of risk، in order to identify the high risk areas، urban management، necessary measures to increase environmental capabilities. an‎d reduce vulnerabilities In this research، effective factors were first identified in the occurrence of each of the flood geomorphic hazards، landslide، earthquake and fluidization. Then، maps were prepared for each of the factors، topographic maps، geology، geological data، seismicity، etc. from different organizations and maps were prepared. After preparing the maps، the fuzzy standardization method (decreasing and incremental functions) was used to determine the effective impact of each of the effective information layers in the occurrence of each of the hazards. In the final stage، considering the factors affecting the occurrence of any geomorphic hazards، weighing to layers based on their degree of importance was carried out using (AHP) method. At this stage، the final weight of each layer was multiplied in the corresponding layer، and then together and the final map of each of the geomorphic hazards was prepared. After mapping each of the geomorphic hazards of the studied cities، weighing and combining earthquake، flood، landslide and fluidization layers، maps of geomorphic maps of the cities were prepared. The study of the geomorphic hazards of the city of Poldokhtar in the south of the province suggests that flood occurrence is considered as the most important threat to the geomorphic city of Poldokhtar. There is also a possibility of liquefaction due to the high groundwater level، especially in the north of the city. In the city of Kohdasht، in the west of the province، the risk of flood events is higher than the other hazards due to the river passing as a drainage of the catchment from the city. Geomorphic hazards in the northern city of northern Lorestan indicate that the central part of the city is at risk of landslide and liquefaction and parts of the north، west and south are exposed to flood. The probability of occurrence of geomorphic hazards in the area of Alshatr in the north of Lorestan province is low. So that the northwest and eastern parts of the city are risk free and in other parts، the risk of geomorphic hazards is moderate and low. Surveying the risks of Boroujerd city indicates that parts of the West of the city that are in high risk of flood، landslide and liquefaction are known as high risk areas and southern regions as low risk areas. Also، among the threats of Borujerd city، the probability of an earthquake due to the crossing of the young Zagros fault from the Silakhor plain is more than the other geomorphic hazards. In the city of Azna، the risk of flooding is considered to be the most significant danger to the city، although there is a likelihood of landslide and fluidization. The study of geomorphic hazards in the city of Aligudarz shows that rivers in the west of the city are exposed to geomorphic hazards، especially flood. In the city of Dorood، the flood event seems more likely than other hazards. The flood event in the central part of the city، which crosses the main rivers، has the highest potential. But in general، the risk of an earthquake is the most important geopolitical risk in the city of Dorood. In the city of Khorramabad as the capital of Lorestan province، the southern parts of the city have the highest geomorphic risk due to the high potential of flood and liquefaction. Also، the flood risk is considered to be the most important geomorphic risk in the city. The study of geomorphic hazards in the major cities of Lorestan province suggests that there is a probability of occurrence of hazards in urban areas، but the types of hazards are different in cities located in the west and east of the province. Studies show that there is a potential for flood events in many cities، especially in southern cities and Khorramabad، in the capital of the province. Cities located in the east of the province (Doroud، Azna and Boroujerd) have a high density of earthquake occurrence due to the fact that they are located in the zone of the young Zagros fault and the Seychelles seismic quake. Nevertheless، according to geological formations، there is a possibility of landslide occurrence in the cities of Khorramabad and Aligudarz. The likelihood of occurrence of liquefaction occurrence in the studied cities is higher، especially in the eastern province of the province، because the urban areas are mainly located in plains with high groundwater and alluvial soils. The final results show that the risk of flood in the western regions of Lorestan province and the earthquake in the eastern provinces of the province are the most important threats to geomorphic cities.