LANDSLIDE ZONATION IN FASHAM AREA OF TEHRAN PROVINCE (IRAN) Shadi Khoshdoni Farahani, Assoc.Prof.Dr.Md Nor Kamarudin, Dr. Mojgan Zarei Nejad Faculty of Geoinformation Science and Engineering, Universiti Teknologi Malaysia 81300 Skudai, Johor, Malaysia Email: [email protected] Faculty of Geoinformation Science and Engineering, Universiti Teknologi Malaysia 81300 Skudai, Johor , Malaysia Email: [email protected] GIS Center, Solvegatan 12, 223 62 Lund, Lund University, Sweden Email: [email protected] ABSTRACT Tehran province which encircles the capital of the Islamic Republic of Iran is highly momentous from the politico- socio-economic-cultural aspects. This significance has instigated the implementation of the geological, geographical and climatological studies in this state in a comprehensive and precise manner. Fasham district in the north eastern part of Tehran province which is a geologically and geographically area has been opted out in this research for semi- detailed studies. the case studied in this research is the landslide in Fasham area. Iran is one of the highly landslide prone countries due to its particular geological, topographical and climatological conditions. Heavy financial lost are reported each year due to the landslide occurrence. The transpiration of these landslides occasionally brings about other death tolls and financial lost originating from earthquakes. Some of the factors affecting this phenomenon are as follows: the alteration of the slope amplitude, geotechnical and litho logical circumstances, earthquake and trembling, tectonics motions, structural alterations, pluvial effects and snow thawing, the extermination of the vegetation, land utilization alteration. The zone under studied is prone to landslide due to various reasons such as possessing special geological conditions and special geographical position. In this research with using of ArcGIS 9 software and Index overlay Method the landslide prone zones will be anticipated in Fasham area. A GIS-based geographical database is developed to identify landslide and can be used in any decision making in future. KEYWORDS: Tehran, Fasham, Landslide, Geology, Geography, ArcGIS INTRODUCTION Iran is one of the highly slide prone countries due to its particular geological, topographical and climatological conditions. Heavy financial lost are reported each year due to the landslide occurrence. The transpiration of these landslides occasionally brings about other death tolls and financial lost originating from earthquakes. Some of the factors affecting this phenomenon are as follows: the alteration of the slope amplitude, geotechnical and lithological circumstances, earthquake and trembling, tectonics motions, structural alterations, pluvial effects and snow thawing, the extermination of the vegetation, land utilization alteration such as transformation of forest land into roads, express ways, the culture type recasting, the transfiguration of the steep regions to residential and industrial districts, etc. The zone under scrutiny in this study is prone to landslide due to various reasons such as possessing several aquifers and special geographical position. The landslide classification is momentous in the aforementioned district. This geographical region is selected because of its special climate and atmosphere, its location in central part of the ASPRS 2012 Annual Conference Sacramento, California March 19-23, 2012 Alborz, its slopes and special directions of slopes regarding the absorption of solar radiation, and its geological conditions with regard to types of stones and soil. The north eastern section of Tehran or Faham area has been highlighted due to various reasons such as possessing orchards, pleasant climate, being situated in the southern slope of the Alborz mountain ranges. Its vicinity to the capital Tehran and many of the population have immigrated to this area. SCOPE OF RESEARCH Tehran province which encompasses the capital of the Islamic republic of Iran is so crucial from the political, social, economic and cultural aspects. The province is located between 34 ◌ ْ and 36.5 ◌ْ northern latitude and from ,to 53.0 ◌ْ eastern longitude (Figure 2.1). It is situated among the provinces of Mazandaran, Ghazvin, Central ْ◌ 50.0 Qom, and Semnan States. This province is one of the key tourist-bearing zones. According to the census in the 1996 the total population in this province was assessed to be about 10. 3 million and 35% of the whole expressways in Iran are situated in Tehran province. According to the latest statistics 40% of the total industrial units are situated in Tehran. Figure 2.1. Study Area (Fasham) locations in Tehran Province. DATA AQUISITION As shown in Figure 2.2, there are several layers for data to be prepared as mention below: a. Topographical information topographical maps bearing 1:250000 scale of the army are plied to peruse the macro-scales. Cartography organization maps whose scale is 1:25,000 are utilized for semi-detailed probes. b. Geology organization maps at the scale of 1:100,000 which have to be digitized for modeling. c. Provision of the altitude model of the region. d. Provision of the acclivity map by means of a Digital Elevation Model (DEM) map of the region. e. The land use map f. Fault map g. Slope map h. Aspect map ASPRS 2012 Annual Conference Sacramento, California March 19-23, 2012 RESEARCH METHODOLOGY The following methods have been applied in order to complete the research as explain in a flow chart and the relevant aims as shown in Figure 2.2. A brief explanation of the methodology is as follow: i) First using the extant layers to digitize some of the available maps data a. Utilization of the topographical maps in the scale of 1:250,000 and 1:25,000. b. Utilization of the geological cartography in the scale of 1:250,000 and 1:100,000. c. Utilization of the land use cartographical entities. d. Utilization of the Geographical Information System (GIS) and Remote Sensing (RS) software for modeling. ii) Making maps originating from basic data and the provision of new topical maps such as the declivity (slope) cartography, steepness direction, geomorphologic maps, isohyetal and isothermal maps, etc. iii) analyses and the producing of landslide hazard zonation map of Fasham area iv) finally, the Conclusion. DATA ANALYSIS AND CLASSIFICATION (PROVIDING OF INDICATOR MAPS) In this section the data analysis carried out as for providing maps such as geology map, Fault map, aspect map, land use map and slop map. To analyze the layers in ARC GIS software using the Index Overlay Method, bearing in mind the extent and level of collected data regarding the layers in the region, and to have precision in studies, all the layers used in this project were divided into five classes based on experts' views. In the first phase, data is labeled either as high risk or low risk in the attribute tables of each layer, with regard to its significant role in occurrence of landslides, and is assigned an even number between 2-10 (Stable-Unstable). This is shown in the legends of re-classed maps as the following table demonstrates: Table 3.1. Base of data classification Data classification Score Equivalent in the maps High risk 10 Unstable Relatively High Risk 8 Relatively Unstable Moderately Low Risk 6 Moderately Stable Relatively Low Risk 4 Relatively Stable Low risk 2 Stable PROVIDING OF GEOLOGY MAP The geology map of study Fasham area is classified into 5 groups which this are based on rocks strength of Fasham area. According to Table (3.2), rocks and stones are classified into 5 different groups and according to their stiffness and strength, per score is added to them. This is shown in map 3.1 ASPRS 2012 Annual Conference Sacramento, California March 19-23, 2012 Table 3.2. Base of Geology Classification of Fasham area Symbol on Group’s No. Rock Unit Score the map name legend Quaternary Unstable 1 Rocks and PIQC, S 10 Sediment 3 2 1 C K sh a m t sh Sedimentary M, M u, M u, M u, O 1, E N, E k, E k, E k, E k, E k, Relatively 2 m,s,s c 3 a 8 Rocks gy, PE f, PE f, PEv, P JS,pd, P j, CZ, Ebt Unstable Kd Kc Kb Ka K Kc Kb Ka Kt, Kc Ja, J Moderatly Calcareous u, u, u, u, 3, 2, 2, 2, 1, 1, 3 Jd, Rd Rl Rm.l Pn, Pr, Cm, Cd Cc Cb Ed PE- 6 Stable Rocks e, e, e, j, j, j, bt, ES Volcanic Relativly 4 Rv Dv , Eq, C , E Tr,MZa,d, Tda, Tb, Td,R 4 Rocks 3, j 1 1, Stable 5 Igneous Rocks Tgr, T8, Td, Tgb 2 Stable In this classification, the most score belong to Quaternary rocks and sediments, that is, Quaternary rocks and sediments are more reliable to happen landslide. Because of the geologically reason Quaternary rocks and sediments are very young, not very stiff, and are unstable. The second group includes sedimentary rocks like Sandstones, Mudstones, Marl, Gypsum and shale. Geologically, the sedimentary rocks are not very strong and belong to unstable rocks group. The third group is calcareous rocks which are more strength than sedimentary rocks; this group includes Limestone and dolomite. The fourth group is volcanic rocks which are in the group of strongest rocks. This group includes Andesite, Andesite- Basalt, Pyroclasticm Quartz, Sandstone, Riolite, Dolerite and Lithic tuff. The fifth group, which is the most strength group of rocks, includes igneous rocks and so give the fewer score is added to this group. There is very little possibility that happen landslide in this group. This group includes Granite, Granodiorite, Siyenite, Diorite, Micro diorite and Gabbros. Finally, the classify map from original map which is vector file, is changes into raster or grid file. After preparing all the attribute tables for all the layers in ARC GIS software, and when the analysis process is complete, it is necessary that all the layers data be turned from Shape file or Vector format into Rater or Grid format for the final process so that they can be merged in ARC GIS software using Index Overlay Method and make the final map.