Early Warning and Evaluating Impacts of Ice and Snow Disasters on Beijing Urban Transportation

Using urban historical damage data of ice and snow from 1952 to 2011, the snow damage grades to Beijing urban transportation operation is built for the assessment on the accuracy of the following ice and snow warning and evaluation model. Based on disaster science principal combining with historical damage data, warning and evaluation indices of ice and snow damage to Beijing urban transportation operation are selected which are time, ice and snow intensity, traffic vulnerability, warning ability and disaster reduction ability. Ice and snow intensity can be determined by snowfall, snow depth and air temperature. Traffic vulnerability is determined by road network density and its time evolution. Warning ablility is mainly determined by weather forecast quality and its information spreading ability. Disaster reduction ability can be estimated by the gross domestic product and its time evolution. From the sensitive of these factors to snow disaster, method of experts marking is applied to computing and grades division of the single related factor and the comprehensive indices. Using judging-matrix of analytic hierarchy process (AHP) method, weights of four comprehensive evaluation indices are computed. Weights of four indices are ice and snow intensity with 0.4404, traffic vulnerability with 0.2789, disaster reduction ability with 0.1797, time with 0.05264 and warning ability with 0.0484, respectively. And Beijing urban ice and snow disaster warning and evaluation model is also constructed using AHP method. Using the model, 38 samples of historical ice and snow disaster events in Beijing are evaluated. The total accuracy is 76% and the accuracy in recent ten years (2002—2011) is 89% which shows the model can simulate effectively the impact of ice and snow disaster on Beijing urban area. The analysis of index weights shows that the hazard factor is still the major factor but not the only determinant factor of urban ice and snow disaster, as the total contribution of the other four factors to snow disaster overtakes the contribution of hazard factor. The ice and snow intensity as hazard factor affects Beijing urban transportation operation together with other factors under urbanization process such as transportation and disaster emergency management. The analysis of assessment on historical snow disaster events shows that under the influence of other factors, even light snow is able to cause serious damage on urban transportation operation and heavy snow perhaps only has medium effects.