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Geohazard Assessment of Northern Pakistan

The Landslide Susceptibility Map represents the probability of the occurrence of Landslides based on the parameters included and which was validated by the success rate of analysis prediction with the present landslide inventory. The goal of the analysis was indirect prediction of the spatial landslide occurrence probability.

The output scale of the map is 1:50,000 which is suitable for a regional overview of the landslide susceptibility and selection of areas for further investigations on a larger scale, if required. With the help of ArcGIS 10 along with two of its extensions, Spatial Analyst and Geostatistical Analyst, a spatial analysis was executed based on a statistical modeling aproach.

The Susceptibility map of Balakot area was developed by using the Weight of Evidence (WofE) method which belongs to the bivariate statistics methods based on the theorem of Bayes. The dependence of different parameters to the occurrence of known (observed) landslides was analyzed whereby each of the parameters was assumed to be statistically independent from the others.

The final map represents the overlay of weighted parameter maps: lithology, landcover/landuse, slope, Normalized Differenced Vegetation Index, geomorphologic features, distance to river and distance to streams.
Five zones of susceptibility were distinguished in the map ranging from very high to very low.

GSP´s role in Landslide Susceptibility Assessment in coordination with Disaster Management Authorities is to develop a standard approach and method for susceptibility assessment of mass movements/landslides providing maps on regional scale to determine areas of priority for intervention, development planning and disaster mitigation (as far as the availability of input data allows). The availability, quality and meta-information of digital data is one major concern in the project as the scale of the input data defines the maximum scale of the output maps and therefore the possibilities of detailed susceptibility.

Assessment on a sound scientifically based statistical approach. Geospatial data, whether analogous or digital cover the whole country comprehensively only in small scales. Detailed information for assessments is not generally available. Therefore this method cannot be performed in every region. The consequence of using this map in the District and Local Administration is NOT a general evacuation of people living in the areas of very high susceptibility but having a basis for risk-sensitive Development planning which is considered a need of the time to fulfill the governmental task of safeguarding its population. Instruments of land-use planning, regional planning and settlement planning are already laid down in the Local Administration Framework as task of the Tehsil Administration but they are not generally and bindingly implemented yet. Development planning that takes into account disaster risk reduction will hence decrease potential future losses to physical assets, environmental capital, institutional assets, and human life but requires standardized planning processes.

This could be initiated by Standard Operation Procedures or a regulatory framework combined with a training of the respective Administration Departments on different levels (from Tehsil up to Provincial level at least) implementing the mandatory use of this map in every future intervention in this region. The areas very susceptible to landslides need to be handled differently from the areas with a very low or low susceptibility of landslides. In areas that show a high susceptibility for landslides, construction of infrastructure, official buildings and settlements have to be assessed and approved by specialists before construction starts in order to make sure that future losses are minimized as much as possible.