Spatial Analysis of Environmental Hazards

Spatial Analysis of Environmental Hazards

Analysis and Assessment of Landslide Vulnerability in Mountainous Hillsides of Tehran Metropolis

Author
Amir Saffari
Abstract
Today, urban and regional issues related to sustainable development is a key challenge for policy-makers, planners and specialists in various disciplines. Geomorphologic studies can be useful and effective in analyzing and deriving acceptable means to assess the growth and development of the city, and to set criteria to determine the directions of urban development. Landslides range of motions not only affect the human structures such as roads, rail lines and residential areas, but also lead to casualties. Tehran metropolis mountainous basins, including Kan, Vesk, Farahzad, Darake, Velenjak, Darband, Golabdare, Darabad, Sorkheh-Hesar, and Sohanak due to the lithology, geologic structure, weathered sediments, steep slope, rainfall and poor urban development are considered as one of the places where landslides are a range of geomorphologic processes can be studied. At this research, using Fuzzy and AHP methods and by the use 8 factor variables such as lithology, elevation, slope, aspect, annual rainfall, maximum daily rainfall, distance from fault and drainage system. the map of landslide zonation hazard in mountainous areas of the city is prepared to determine risky strips. After the standardization of the criteria for the occurrence of landslides and using frequency ratio method and fuzzy model and functions, Landslide hazard zonation maps was prepared for evaluating from the fuzzy sum, fuzzy product and fuzzy gamma operator 0.8 and 0.9. Then the final map of landslide zonation, obtained from the above-mentioned method matched with the map of urban regions in mountainous areas. In this way the constructed region have been distinguished from very high and very low hazard zonation. Lithological studies showed that most of the basin areas covered by Karaj Formation. About 45/7 percent of units with sliding movement in areas with "rock crystal tuff and tuff lytic green, with the layers of limestone" (unit Et2) of the intermediate tuff formation occurred. Cross of faults distance map with landslide density map showed that about 33/1 percent of landslides occurred within 200 m of the fault lines and 78/4 percent of landslides occurred within 500 m of drainage network. Most sliding movements (60/2 percent) in the range of 1900 to 2500 meters altitude and about 35/3 percent of this type of range of motion in height of 1500 to 1900 meters occurred. This area is about 81/6 percent of sliding movements in slopes between 15 and 40 degrees (26/8 to 83/9 percent) and about 17/6 percent on slopes less than 15 degrees (26.8 percent) occurred. In the aspect, sliding movements of the basin, mainly in the south-western slopes (about 23/2 percent), the South (about 17/5 percent), West (about 16/6 percent) and Southeast (about 77/1 percent), northwest (about 33/1 percent) occurred. About 88/9 percent of sliding movements in areas with average annual rainfall of 244 to 280 mm occurred. According to the zoning map, 12 percent of mountainous basins area (approximately 10,057 acres) is in the zone of very high risk, 33 percent (approximately 27,723 acres) is in high risk areas, 20.5 percent (approximately 17,143 acres) in the moderate risk zone, 30/ 7 percent (approximately 25,672 acres) in area and 3.8 percent of the total area of the basin, low risk (approximately 3172 acres) located in low risk areas. The results showed that approximately 5.2 hectares (about 0/05 percent) of the urban in zones with a huge landslide, about 51/5 acre (approximately 1 percent) in zones with high landslide risk and about 821 acres (equivalent to 25/16 percent) in the medium risk landslide zones are located and developed. The final results indicate that some mountainous regions of Tehran Metropolis are apt to landslide with middle to high risk. (Apart from strengthening the vulnerable area) avoiding these areas is an important solution to decrease damages caused by landslide.
Keywords
Urban Development
Vulnerability
Landslide
Multi-Criteria Decision Making Models
Tehran Metropolis
Alimohammadlou, Y.; Najafi, A. and Gokceoglu, C. 2014. Estimation of rainfall-induced landslides using ANN and fuzzy clustering methods: A case study in Saeen Slope, Azerbaijan province, Iran. CATENA, 120: 149-162.
Dragićević, V.; Lai, T. and Balram, S. 2015. GIS-based multicriteria evaluation with multiscale analysis to characterize urban landslide susceptibility in data-scarce environments. Habitat International, 45: 114-125.
Faraji Sabokbar, H.; Shadman Roodposhti, M. and Tazik, E. 2014. Landslide susceptibility mapping using geographically-weighted principal component analysis. Geomorphology, 226: 15-24.
Feizizadeh, B.; Shadman Roodposhti, M.; Jankowski, P. and Blaschke, T. 2014. A GIS-based extended fuzzy multi-criteria evaluation for landslide susceptibility mapping. Computers & Geosciences, 73: 208-221.
Komac, M. 2006. A landslide susceptibility model using the analytical hierarchy process method and multivariate statistics in per alpine Slovenia. Geomorphology, 24: 17-28.
Shahabi,M.; khezri, s.; ahmad,B.B and Allahvirdiasi, h. 2012. Application of satellite images and fuzzy set theory in landside hazard mapping in central zab basin. IOSR Journal of applied physics, 1: 17-24.
Van Westen, C.J. and Terlien, M.T.J. 1996. An approach towards deterministic landslide hazard analysis in GIS: A case study from Manizales (Colombia). Earth surface processes and landforms, 21: 853-868.
Zhang fanyu, L. 2007. Study on Landslide susceptibility Mapping Based on GIS and With Bivariate statistics a case study in London area highway 212. Science paper online.
Yalcin, A. 2008. GIS-based landslide susceptibility mapping using analytical hierarchy process and bivariate statistics in Ardesen (Turkey): Comparisons of results and confirmations. Catena, 72: 1-12.