Evaluating the Prioritization of Transportation Network Links under the Flood Damage: by Vulnerability Value and Accessibility Indexs

Abstract

Flood does not leave equal impacts on the transportation network links. Each link of the network demonstrates a different level of resistance against flood based on its hydrologic and structural design. The purpose of the present investigation is to determine vulnerability value and merge that with the accessibility index for strengthening the transportation network links against flood. The Golestan province was chosen as the case study. In this study, for evaluating of vulnerability value, the flood peak was determined based on the maximum daily discharge. In order to assess the flood peak for different return period's frequency analysis (HYFA) software was used. Finally, the vulnerability value as a result of destruction of the bridges due to flood was determined. For evaluating accessibility indexs, the roads network was modeled by EMME2 software and then, the network was loaded based on travel time and traffic volume. The accessibility indexs based on the travel time and traffic volume was determined and assessed before and after flood. The vulnerability value is utilized as a coefficient for the accessibility indexs in the study. According to the obtained values, the prioritizations of the different network links were prioritized in the occurrence of flood. Evaluation of prioritization of different links of road network has been determined based on vulnerability value multiplied by accessibility index. Generally, it can be concluded that merely using the accessibility index does not suffice in prioritizing the transportation network links against flood. Consequently, another index needs to be assessed simultaneously with the accessibility index. This index is in fact the vulnerability value of the destruction of the bridge due to flood. In the composed index, a merged form of these two proposals has been presented. Key word: accessibility indexes, bridges, flood peak, return period, vulnerability value, traffic volume and travel time