Simulation of Evacuation Behavior in the Event of River Flooding

<p>1. Introduction</p><p>Human society has developed in connection with rivers. This is also the case in Russia. Seasonal changes in flow rates are observed in Russian rivers, mostly accompanied by spring floods. This is mostly due to snowmelt, which is the largest hydrological seasonal phenomenon in Russia and affects all sectors of the economy. In addition, a unique phenomenon called "ice jam" occurs during the spring flood season, in which the downstream of a northbound river is iced over while the upstream is iced over, resulting in flooding at the boundary between the iced over and iced over areas (Kurashima, 1963, Hydraulic Science). The city of Tomsk, with a population of about 570,000 and an area of 295km², is located in the western Siberian lowlands, about 50km² upstream of the confluence of the Tom and Obi Rivers. The Tom River is a tributary of the Obi River, which flows through Siberia. The Ushayka River runs east-west through the city, and the Tomi River runs north-south through the west side of Tomsk. In recent years, the Tomy River basin was severely damaged in 2010. Therefore, there is an increasing need for disaster prevention measures in Tomsk city. In this study, we developed an inundation model and conducted a network analysis of residents' evacuation behavior around the Ushayka River, which flows through Tomsk city.</p><p></p><p>2. data and analysis method</p><p>We downloaded the road and building data of the target area from OpenStreetMap, and used the numerical elevation data from SRTM provided by NASA, which was projected and converted to a 20m mesh of the target area. In addition, the land cover data containing each attribute including the city of Tomsk was used to set the roughness coefficient values for use in the inundation model. For the inundation model, a two-dimensional unsteady flow analysis based on the dynamic wave model, which is characterized by its ability to track the movement of expansive water, was used.</p><p>As for the evacuation behavior, since the attributes of the residents were not available, we simulated their arrival at the nearest evacuation site based on the buildings used for residential purposes. Two simulation patterns with different number of evacuation sites were conducted, and the results were analyzed before, 2 hours, 4 hours, and 6 hours after the flood. We also calculated the travel time from each evacuation site to each hospital in order to study the movement in Tomsk after the flood. This was also analyzed before, 2 hours, 4 hours, and 6 hours after the flood.</p><p></p><p>3. Results</p><p>Figure 1 shows the simulation of evacuation behavior after 4 hours of flood occurrence and consideration. As the initial value in the inundation model is no water flow, the flood flow of the Ushaika River joined the Tomi River at 4 hours of flood occurrence. The flood waters of the Ushayka River expanded its waterlogged area up to 6 hours after the onset of flooding, but there was no significant change after 6 hours.</p><p>In terms of evacuation behavior, the city of Tomsk was divided into north and south by the floodwaters of the Ushayka River after 4 hours, when the Ushayka River, which runs east to west through Tomsk, joined the Tomi River. In terms of the number of evacuated buildings, more than 1,000 buildings could not be evacuated four hours after the flood. Therefore, if people do not evacuate before the Ushayka River overflows, it will be difficult for them to move between north and south due to the flooding of the Ushayka River. In addition, depending on the analysis on the attributes of the residents, evacuation is expected to take a long time.</p>