عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Landslide is a natural phenomenon that occurs due to falling down or movement of sediments materials along the hillsides. Velocity and wideness of the phenomenon cause attractive & tragedy one, which can affect on thousands of cubic meter of soil & stone. This phenomenon is the most Common natural earth change phenomena that occur in the geological period which is nowadays known as natural disaster.
In present decade its importance is considered to deal with natural disaster and to reduce its risk. One of the important objectives of this research is to identify different parameters in landslides of sensitive area.
This project also aims to identify high risk area and low risk area of landslide in order to reduce harmful effects landslide. Therefore, nowadays we need to provide landslide hazard zonation in sensitive areas with unstable hillside because every year it causes huge damages. Therefore, research is necessary for which different methods that give acceptable results by the researchers such as systematic or map query from which statistical method is chosen. In this research, Marbor river basin is zonated by using two variants statistical method which includes value of information and density area
In order to prepare the hazard zonation landslide map, it is necessary first to prepare the distribution map of landslide in the region. This is done by field study and using geological maps, topographic maps, digital elevation model
(DEM) and land use maps using Ilwis software. The obtained data is then transferred to I1wis software and six information layers such as slope, lithology, rainfall, land use, and distance from roads were used. These layers were then intersected, and classified landslide hazard zonation map with 2 statistical method.
This research attempts to zonate the Marbor River domain in the south of Semirom city with an area of 1438 km2 using Binary statistical method because of increasing instability of the slopes and landslide phenomena, to prevent it from human and financial damages. Therefore, by collecting required information on landslides dispersion in the region, landslide dispersion map is provided by preparing six informative layers which includes slope, aspect, lithology, landuse, distance from the road, and precipitation rate. These layers were then intersected, and classified landslide hazard zonation map with Binary statistical method. These methods contain:
1) Information Value
This method is based upon the following formula:
Wi = the weight given to a certain parameter class (e.g. a rock type, or a slopeclass).
Densclas = the landslide density within the parameter class.
Densmap = the landslide density within the entire map.
Npix(Si) = number of pixels, which contain landslides, in a certain parameter class.
Npix(Ni) = total number of pixels in a certain parameter class.
2) Density Area
Afterwards, we analyzed the accuracy and precision of each method (P, QS).
For the analyses and accuracy of the used method, two equations of accuracy and precision are used which are P method and QS method, and to compare the accuracy and precision of the two maps in linear regression and audit analysis, the best method is chosen. These relations are shown:
(P) method's accuracy: Area of land slide in medium and high hazard zone is divided by their area as shown by the correlation:
where, P is method's accuracy in medium and high hazard zones, KS is the landslide area in medium and high hazard zone and S is the related hazard zones area
The (QS) method's Precision is obtained by density ratio as shown in this equation:
DR = percent of landslide / percent of area
The result showed the Infomation value is better than other method for this region.
1. Using hazard zonation map of landslide we can design road networks, technical structures, power lines, gas, etc, in sustainable zones and reduce damage
2. Map prepared by Information value method is an appropriate for Landslide hazard zonation in this area
3- The factors studied show maximum of landslide Have occurred in 12-25 slope, South East, Daryan formation, 500-700 rainfall and and with 0-1500 metter distance to road.
4- Avoid building structures near the river. because in this area has high potential for occurrence landslide.
5- East and South East region have minimum potential for occurrence landslide.