A Methodology for Spatial Flood Risk Assessment Taking Account of Spatial-Temporal Characteristics of Rainfall
In a river basin, if an area is influenced only by one river, the flood risk of this area can be calculated by analyzing the return period of storm or flood of this river. However, many areas in a basin are influenced by more than one river. Then, how to asses flood risk considering spatial correlations among rivers become an important topic. There are mainly two ideas to solve this problem. One is analyze spatial dependence structure directly using the river gauging station data by a joint distribution function. This method is straightforward and explicit, but for many areas, continuous river gauging station data at each reach is not available. The other solution is to adopt rainfall data to estimate the spatial dependence structure of rivers. According to the second idea, the paper aims at proposing a methodology to assess flood risk at each point of river basin which can be affected by more than two rivers. The outline of the methodology is the following: 1. Divide sub basin by using river section and DEM data, extract counter line and other geographical data for hydraulic simulation. 2. Analyze rainfall characteristics in each sub basin to estimate â€œimportant rainfallâ€ and proper spatial distribution strategy. 3. Estimate spatial dependent structure among sub basins by Copula function. 4. Generate theoretical rainfall dataset which considering rainfall characteristics and spatial dependent structure. 5. Use this rainfall dataset drive a distributed hydraulic model to assess flood risk. Also, a case study in Maruyama river basin in Japan is conducted. The paper concluded by summarizing achievement of the study and issues remaining for the future research.
Spatial Flood Risk Assessment; Rainfall Spatial-Temporal Characteristics; Maruyama river basin