A network-based analysis of road network vulnerability and urban space accessibility following earthquake (Case study: the city of Aligoodarz)

According to crisis management cycle, road network substantially play important role in reduction of negative impact of earthquake. In fact, road network fundamentally promotes emergency aids during earthquake and facilitates mobility for citizens after earthquake. This study aims to analyze vulnerability of Aligoodarz's road network and then evaluates urban space accessibility following earthquake. In this regard, combination of graph-theory concepts and GIS-based spatial analysis are used. In the first step, three categories of criteria for the vulnerability of road network have been identified based on the relevant the theoretical foundation. These criteria are relating to vulnerability of build-up area surrounding of roads, topological properties of road network, and functional properties of road network. In the second step, real-world road network is converted to graph network and then the importance of each criterion is achieved based on Analytic Hierarchy process (AHP). In continues, by using AHP's results in GIS spatial analysis, vulnerability map for road network is produced, on a four-point ordinal scale. This map shows that about 42 links which constitute 11.5 percent of total length of roads have the highest degree of vulnerability. In final step, the highest vulnerable roads (links) are eliminated and then urban space accessibility is computed using cost-distance algorithm. The accessibility map also shows that accessibility in some urban areas- mainly central areas- reduces between 40 to 120 meters.