Keywords: Geographic Information System (GIS), Landslide, Land use, Zonation
Abstract Similar to other developing countries, Iran is also suffering from environmental hazards. In Iran, its main reason is population pressure due to higher population growth rate and in-migration. The landslide is one example of such phenomenon that affects the household, road and etc. Under this context, the present study has been carried out to approach for better land use plan. In this regard, the role of land use change and its relation to landslide has been investigated.
Study area is Poshtkoh of Freydonshahr, which is located in southwest of Isfahan in central of Iran. From the point of view of landslide potential, this area has been detected by using geographic information system (GIS). Using the Arc Inf. Software has done this zonation. It is concluded that the most important landslide points has been occurred in the areas which was changed the land use. These changes are mainly in relation to replacement of forest to grassland and also civil activities. There are different agents that cause the landslide. For this reason, different theme maps such as raining rate map, slope map, hypsometry map and aspect map has been prepared. The final map is achieved by composing different theme maps. By using this map, it is possible to classify the area regarding to hazard rate for land use.
1. Introduction
Landslide is a world wide disaster that has murdered thousands of people and damages million dollar every year. In spite of the fact that the landslide is more manageable and more forecastable as compared with other natural calamities like earthquake and flood, there are less than one percent of the countries that have the landslide maps and few landslide stability potential maps have been prepared. In this paper authors have attempted to prepare the zonation map of the Poshtkoh area of Freydonshahr section, which located in southwest of Isfahan in relation to landslide potential by using GIS in order to land-use.
2. General
The studied region is about two hundreds kilometers far from center of Isfahan. This area is equal to 81819.8 hectares between (49 48 45 - 50 19 2) longitude and (32 37 2 - 32 53 48) latitude (figure 1). Regarding to geomorphology of area, mountains cover more of lands about 68.04% equal to 55970.5 hectares. Also hills have 11.42% equal to 9391.86 hectares and traces have 6.83% equal to 5468.6 hectares and cliffs have 13.71% equal to 11361.8 hectares of the total area.
Water-drainage of the studied project are divided in to four basins and some sub basins as follow:
| Main Basin |
A |
B |
C |
D |
| Sub Basin |
--- |
|
|
DE=DE1'DE2'DE3
DF
DH
|
Hydrogeology factors like drainage density, waterflow regimes and etc. cause to mass movement by surface and subsurface erosions. The main rivers, because of more extensive flows, have more potential to washout the deposits and trigger the landslides. For this reasons the landslides which located in the studied area, mostly are around the rivers. Slope morphology is another factor that influences the landslide. Generally the slope alterations are divided in two categories as natural and artificial. Sometimes the rivers washout the slope-toe and unstable it. In other hand, excavations and trenches also could activate the landslides and cause to create a disaster.
One of the important factors that directly increase the landslide potential is precipitation. This phenomenon is in form of snow that is over 50% of precipitation of the area and always occurs at the winter. Eleven classes are considered for the precipitation of this area, which are between 450 to 1400 millimeters.
Destruction of grasslands in addition to land-use changes like replacement of forest and agricultural ground to building, road and other civil structure, is important factor that will cause starting the landslides. The information was collected only around the road because of difficulties to cross the mountains. Twelve important landslides were defined that we pointed them on the map with scale 1:250000.
Since preparing the zonation map of landslide and defining the critical point is via to civil planning, recognition of Poshtkoh landslides was performed by using the geographical information system (GIS) and ARCINFO software. The preparation steps of landslide zonation map are followed.
