Vulnerability Mapping Using Easy AHP _ CBS UYGULAMA

CBS UYGULAMA

AUG 17 2014

Vulnerability Mapping Using Easy AHP

Bu sayfayı Türkçe olarak okuyabilirsiniz. (h�ps://cbsuygulama.wordpress.com/2014/08/17/easy-ahp-ile-zarar-gorebilirlik-analizi/)

One of the fundamental concepts in the disaster management is vulnerability. It refers to losses in theface of any danger. Vulnerability is discussed in different views like economic, social and physical etc.GIS-based disaster management studies mostly focus on mapping of physical losses that may occur.

There are different technics for making vulnerability maps for an area. In this field, AHP (AnalyticHierarchy Process) appears as a rational method. I prefered AHP for making vulnerability map in myM.Sc thesis.

Fundamentals of GIS- based AHP are comparing each of map layers and determining weight values. Inthis way decision makers could choose suitable result by defining a hierarchy for complex problems .

Sample Application

In this application, vulnerability analysis was performed for an area in the district of Sarıyer, Istanbul.Initially layer weights were calculated using AHP and vulnerability map generated by WLC (WeightedLinear Combination) analysis. I have developed Easy AHP plugin for QGIS and all of the analysisprocess were realized by using it. The analysis area and the map layers are shown below.

(Bina = Buildings; Elektrik Ha�ı = Power Lines; Fiber Hat = Telecom. Lines; Karayolu = Highway)

Vulnerability Mapping Using Easy AHP | CBS UYGULAMA https://cbsuygulama.wordpress.com/2014/08/17/vulnerability-mapping-...

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Preparing Analysis Layers (Parameters)

In AHP literature input layers are called as “parameters”. Fistly input parameters were generated frommap layers.

Bina (polygon) > Bina yoğunluğu (Building density) (raster)

Elektrik Ha�ı (line) > Elektrik Ha�ına Uzaklık (Distance to Power Lines) (raster)

Fiber Hat (line) > Elektrik Ha�a Uzaklık (Distance to Fiber Lines) (raster)

Karayolu (line) > Karayoluna Uzaklık (Distance to Highway) (raster)

To generate building density you can produce centroids and run kernel density analysis. For generatingdistance maps you can use proximity or multi-buffer tools. In this application main objects are AHP andWLC analysis. So I dont mention much about preparing map layers (parameters). Also I recommendthat your map layers must be in same CRS. Otherwise yo can get incorrect resuts.

The generated parameters are raw so they could not used in WLC analysis after AHP. Because they aredefined in different units (building densitiy and distance). They must be classified and converted to sameunits. I recommend r.reclass tool for this job. Distance to Fiber Lines, Distance to Power Lines, Distanceto Highway were classified as 25m, 50m, 100m, 150m, 200m, >200m six classes. And Building Densitywas classified as six classes in the face of building distrubution. These four parameters are shown below.


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(h�ps://lh4.googleusercontent.com/-E6-Ed-VMgpw/U_CcE7dxokI/AAAAAAAAAmA/W0SdMFLD2H8/w642-h516-no/Fiber_ZG2.jpg)

(h�ps://lh4.googleusercontent.com/-E6-Ed-VMgpw/U_CcE7dxokI/AAAAAAAAAmA/W0SdMFLD2H8/w642-h516-no/Fiber_ZG2.jpg)


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(h�ps://lh6.googleusercontent.com/-TVBgYSW447Q/U_CcE0Ww_aI/AAAAAAAAAl8/lW4lhxFiDvQ/w612-h516-no/Bina_ZG2.jpg)

(h�ps://lh4.googleusercontent.com/-r4YhVTmwXjY/U_CcHmbWS_I/AAAAAAAAAnA/9JrRU4iT-Pw/w640-h516-no/Karayolu_ZG2.jpg)

Easy AHP

After classification and generating parameters, we pass to next step for calculating parameter weightsusing EasyAHP.


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Start the plugin and click Next bu�on after reading descriptions. In this step choose the analysisparameters. Note that AHP analysis requires 3 parameters at least and not more than 15.

(h�ps://lh6.googleusercontent.com/-pLnylQRfW3U/U_CcI2h-_HI/AAAAAAAAAmc/cmKniPf-qB4/w626-h513-no/2.png)

In the second step we fill the pairwise table. During comparion between parameters you can use 1 to 9numbers. Greater numbers means more importance (Saaty, 1980). Also notice that cross cell are filledautomatically. After filling all the cells, click Calculate bu�on for calculating AHP indicators. Note thatCR value must be less than 0,1. If not the pairwise table is considered as inconsistent (Saaty, 1980). Thesample pairwise table is shown below.


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After calculating AHP indicators move to next step. Now we run WLC analysis using output layerweights of the AHP for generating vulnerability map. In this step Easy AHP uses Processing Toolbox’sSAGA Raster Calculator tool. Deafultly it installed by QGIS but make sure it runs without error. ClickBrowse bu�on for output location and Run the analysis. After finishing the process, result layer is addedinto QGIS canvas.


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In this application sample vulnerability map was generated using Easy AHP that combines AHP andWLC complex analysis. The result maps are shown below.

(h�ps://lh3.googleusercontent.com/-GEjl3anmzKs/U_CcIGSc89I/AAAAAAAAAm8/a5zFiMmEhKo/w601-h516-no/Son2%2B-%2BKopya.jpg)


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By MSbilgin • Posted in Python, QGIS, Raster Analizleri • Tagged Afet yönetimi, AHP, zarar görebilirlik

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Vulnerability Mapping Using Easy AHP _ CBS UYGULAMA