ارزیابی ریسک زمین لغزش با رویکرد ژئومورفولوژی در حوضه کالپوش (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
زمین لغزش ها تأثیرات منفی زیادی بر زندگی اجتماعی و اقتصادی مردم جهان دارند. هر ساله در بسیاری از کشورهای جهان، زمین لغزش ها خسارات زیادی را به روستاها و شهرهای کوهستانی و سازه های انسانی مانند ساختمان ها، جاده ها، خطوط انتقال نیرو و ... وارد می نمایند. در این پژوهش، ریسک زمین لغزش با رویکرد ژئومورفولوژی پیشنهادی در جهت کاهش آسیب پذیری عناصر در معرض خطر برای حوضه بحرانی کالپوش سمنان مورد ارزیابی قرار گرفت. با استفاده تلفیقی از داده های عکس های هوایی قدیمی، تصاویر ماهواره ای و نقشه برداری میدانی، زمین لغزش های گذشته و حال و تغییرات مورفولوژیکی آنها در یک دوره زمانی 54 ساله شناسایی شد و در نهایت نقشه موجودی زمین لغزش چندزمانه تهیه گردید. سپس ویژگی های مورفومتریک، نوع، سرعت، شدت، فراوانی، مناطق خطر، عناصر در معرض آسیب پذیری و ریسک زمین لغزش، شناسایی و مورد تحلیل قرار گرفت. نتایج این روش نشان می دهد که 109 زمین لغزش با زمان وقوع نسبی متفاوت (قبل از سال 1347 تا 1401) در حوضه کالپوش وجود دارد. قدیمی ترین آنها(قبل از سال 1347) دارای مساحت، عمق، حجم و شدت بیشتری بوده، بنابراین در صورت فعالیت مجدد خطر زیادی برای منطقه خواهند داشت. 9 منطقه با ریسک لغزشی بالا به صورت متمرکز در جنوب و غرب حوضه کالپوش شناسایی گردید. روستای پرجمعیت حسین آباد نیز به طور کامل در پهنه ریسک لغزش بالا با شدت و فراوانی زیاد و احتمال آسیب پذیری ساختاری و عملکردی زیاد سازه ها(ساختمان ها و جاده) قرار دارد. بنابراین توسعه و ساخت و ساز مجدد روی این پهنه، با احتمال فعالیت مجدد آن در آینده، این منطقه را مخاطره آمیز می کند.Assessment of Landslide Risk with a Geomorphological Approach in the Kalpush Catchment
Introduction In recent years, due to heavy rainfall affected by climate change, global warming, and human activities, the occurrence of landslides and the reactivation of old landslides have increased, and every year in many countries of the world, landslides cause great damage to human structures such as buildings, roads, power lines, etc. There is no systematic information on the age, type, frequency, and distribution of landslides in the world, so the lack of this knowledge will have negative consequences. Therefore, preparing an inventory map of landslides, assessing the risk and hazard of landslides for areas with a high concentration of landslides is important for predicting and preventing future hazards. One of the applications of landslide inventory maps is in landslide hazard and risk studies. Landslide hazard and risk assessment is a complex operation that requires the combination of different geomorphological and geological techniques This research, by combining historical geomorphological data, remote sensing, and field studies with the proposed method of Cardinali et al. (2002), studies the hazard and risk of landslides in the Kalpush catchment and predicts the vulnerability of elements in order to plan and reduce future damage. Methodology The Kalpush Catchment is located in the north of Semnan province and adjacent to Golestan province. This Catchment is located in the east of the forested heights of the cities of Galikash and Minoodasht in Golestan province. The research method used in this applied research and based on a systems approach using library, field survey and remote sensing methods. First, an inventory map of landslides was prepared from historical images and field survey. Then, the relative age of the landslide event, geometric and morphological characteristics, type of landslide, etc. were calculated. After collecting the above documents, the landslide hazard and risk assessment was carried out in 5 stages using the geomorphological method proposed by Cardinali et al. (2002). Results and Discussion 109 landslides with an approximate area of 11 square kilometers were identified, which constitute 10 percent of the total basin. These landslides are concentrated in the south and southwest of the Kalpush basin. The landslides were divided into 4 classes based on the relative time of occurrence (54-year period), image dates, rainfall events of 2018-2019, and the decrease in the water level of the Kalpush dam lake in 2021: before 1968, 1968-2019, 2019-2021, and 2021-2022. 66 percent of the landslides in 2019-2021 and 55 percent of the landslides in 1968-2019 occurred on landslides older than 1968. All new landslides in 2021-2022 were also formed on the shores of the dam lake. According to the type of landslides in the Kalpush Catchment and based on the classification of Cruden and Varnes (1996), 98 percent of the landslides (107 cases), which include creep, rotational, translational, and lateral spreading landslides, have slow movement, and only 2 debris flows in the group of landslides in 2019-2021 have rapid movement. Therefore, almost all landslides in the Kalpush catchment have occurred with slow speed and movement from the past to the present. Deep landslides older than 1968, which were probably affected by different geomorphological, climatic, and earthquake conditions at the time of occurrence, had high intensity and relatively low frequency of occurrence at the time of formation and formed 8 landslide hazard zones. These zones have been reduced to 5 zones for deep landslides in 1968-2019 and 2019-2021, and the reactivation of landslides has less intensity and more frequency, so that they showed a variable landslide hazard and the landslide of Hossein Abad village recorded the maximum landslide hazard. The elements at risk of Kalpush and the location of landslides, the villages of Hossein Abad, Gushhe Degarman, and Korang, due to their high population and density and the roads leading to them, have a higher potential vulnerability hazard (V). The results of the landslide risk zoning map show that there is no area with very high landslide risk in the Kalpush basin due to the absence of rapid landslides (collapse, etc.). Also, Hossein Abad village is completely located in the high landslide risk zone. High landslide risk (R3) refers to areas with slow landslides with high intensity and frequency, high probability of structural and functional damage to structures and infrastructure, and less risk of death. Part of Karang village is located in the medium landslide risk zone (R2). Medium landslide risk (R2) refers to areas with slow or rapid landslides with mild intensity and superficial vulnerability. The results of the above discussions show that in the Kalpush basin, 9 landslide hazard zones (LHZ) with an area of 17 square kilometers have been identified in a concentrated manner in the south and west of the basin Conclusion The proposed geomorphological method is a specialized, accurate, and efficient method that has different responses in different locations. This method is based on the geomorphological observations of experts and the preparation of a multi-temporal landslide inventory map. If the older landslides, their morphological pattern in the region, and aerial photographs are evident, this method can be used. Also, this method is reliable and cost-effective for different scales of watershed, provincial, city, and village. As in this research, it provided the correct answer for the Kalpush basin and its villages. Therefore, it is suggested that given the complete presence of Hossein Abad village in the high landslide risk zone, the village be completely relocated to reduce the probability of vulnerability of elements at risk of landslides in the future. Also, this method is introduced and proposed as a reliable and compatible method for geomorphologists, engineers, and crisis management in the Alborz and Zagros slopes of Iran.
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