Evaluating the Potency of City Crossovers Network with the Approach of Crisis Managing by using GIS

On account of assessing the intensity and rating of risky urban areas, it is essential to provide vulnerability mapping and location data in connection with land use, population, roads, municipal facilities. One of public spaces, services and strategic location in the city are streets and public ways that must be properly designed and planned. Vulnerability of public ways in a town effectively increase the vulnerability of it. In the phase of returning city to normal situation, communication network has an essential role in the travel and transportation between the residence and workhouse, Transportation of cargo and accelerating the normalization of activities. A crisis management strategies to deal with the damage caused by natural disasters in cities is consideration of transportation network. Hence, this study evaluates the vulnerability of the communication network against earthquake, in zone 1 of Kerman. After that by designing the geometric network of the roads and Considering the vulnerability of each roads, the best roads is determined to rescue victims of the crisis via analysis of geometric network of the roads in the environment of geographic information system or GIS.
The purpose of this study is identification and separation of affecting factors on vulnerability urban streets and quantify the effect of each factor on the level of roads vulnerability. In this research, the ratio of vulnerability in the format of urbanism criteria is evaluated according to previous studies and a list of vulnerable elements of urban communication network is provided. Then the final list is completed and developed by using the Delphi method. Delphi method is used with survey of familiar experts with the issue. Based on the list of vulnerable elements in the format of three main criteria (Table 1) were prepared and after binary comparison with the Analytic Hierarchy Process (AHP) and by using software Expert Choice, The importance (Weight) of each criterion were determined and map of vulnerable roads of study area in GIS environment were prepared by overlapping the (geometric mean) vulnerable layers. Finally, with designing of geometric network of urban streets vulnerability of them in Kerman during and after the crisis occurrence were obtained in communication network analysis to rescue and to transfer victims.
1.Mapping the vulnerability of street network
Model of Kerman communication network vulnerability that was used in this study consists of three phases: awareness, design and selection.
Awareness Phase
In awareness phase, modeling of the vulnerability Region 1 Kerman, and identifying of criteria of vulnerability way in the earthquake were performed via Delphi technique.
Design Phase: production of decision options
In this study, urban street network in Region 1 Kerman town are decision-making options, which have been provided by maps to a scale of 1: 2000 and have been prepared by applying Aerial Mapping methods (photogrammetry) with land surveying.
Optional phase: evaluating of options for decision-making (mapping any of the criteria of vulnerability)
After extracting the indices of vulnerability and production options, the final vulnerability of the options must be calculated. The streets network vulnerability of this region of study is dependent to several indices which one of them has a relative importance in comparison with other indices. It is obvious that to calculate the final vulnerability of each way must be determined firstly the weight of indices. Then vulnerability of each way is calculated by calculating the weighted average for each vulnerability index. What is performed at this stage is calculating the weight of indexes and the weighted average vulnerability of each option by using the AHP method.
2.Vulnerability map
Considering the vulnerability is dependent on several parameters that tailoring to each index can be produced the vulnerability map. Finally with overlapping or combination of vulnerability maps can be reached to final vulnerability map. So in the end, the weight of all indices calculating in Expert choice and Excel software, are entered in ArcGIS and by using analytic functions (the intention of using analytic functions were functions overlapping (overlay) that the ARCGIS software was used weighting overlay tools). All maps of vulnerability criteria streets (before phase) are multiplied and combined in their weights. Thus, the final vulnerabilities map of communication network Region 1 Kerman was obtained.
3.Design and construction of roads in the study area
After determining the vulnerability of streets network for emergency services and conveing victims faster during and after the crisis, a geo-referenced database was designed to ways of Region 1 Kerman. At first, a database site called Kerman.mdb created and then three feature classes of data was made that within the database for each dataset were included in it. Then relationships between classes which there are in the real world were modeled at the Geodatabase by the classes of relationship. Topology rules are defined To find errors in input data and avoid false edit data in future. At first, the ways of the region based on the type and length were classified into three groups of the alley, side street and main street. Then in urban thoroughfares Layer Descriptor tables, fields of ways streets vulnerability with fields of name, ID, commute time, unilateral and bilateral street, classification and length of streets and the relevant descriptive information have been filled.
The results showed that according to the old texture Area 5 of Region 1 Kerman and low indexes of urbanization in the area, poor condition of buildings in terms of quality and date of their construction, high density constructions and residential buildings, the vulnerability of the network in the area is high. The map also indicates, due to high density building and being too vulnerable infrastructure in the area, vulnerability is about 90 percent of the ways in zone 1. As well as vulnerabilities is more in old parts and less width roads and ways. On the contrary, in regions 2,3 and 4 on account the relatively new buildings and more appropriate urban indicators, wider roads network and relatively more open spaces, the streets network has less than 35 per cent vulnerability. This highlights implies the need to revise laws and regulations to determine the density and maximum building height (by taking the width of the adjacent street) and the need to emphasis on the quality of urban construction than ever before. Determining the relative importance (weight) criteria by AHP hierarchical process showed that proximity to vulnerable equipment, such as a gas station or gas plant and the width of roads and ways have utmost importance. Criteria Slope and curvature streets and kind of using of buildings and the number of crossing roads and ways have the least important factors to determine the level of roads vulnerability. It can be concluded that the vulnerability of urban roads and paths in approach of earthquake disaster, do not caused by a particular vulnerability criteria but the outcome of the factors and criteria that together provide vulnerability analysis paths.