Application Of MIKE21 FM In Flood Hazard Mapping

Flood hazard map, as an important flood control non-engineering measure, is an essential tool and basis for flood risk management. In recent years, the preparation of flood hazard map of key areas in China has been completed in succession. Many mature hydraulic models have been developed in international community currently, MIKE21 FM model has been widely used in flood hazard mapping in our country because it is simple, rapid, accurate with good visibility, etc. Since MIKE21 FM model is not developed for the preparation of flood hazard maps, there are many problems during its application. In this paper, Luanhe right-bank flood protected zone flood hazard mapping was chosen to investigate the constructing process and key issues of flood routing model based on the requirement of the flood hazard map preparing and the characteristics of MIKE21 FM model. The main research results are as follows:(1) Firstly, the basic build process of flood routing model is summarized based on the characteristics of MIKE21 FM along with the requirement of flood hazard map making. Then issues in modeling process including the adding mode of buildings and its condition, the setting of depth threshold in flood duration and mesh size are discussed in detail. An efficient calculation method using MATLAB and DHI MATLAB Toolbox is presented which overcomes the shortages of MIKE21 FM, including the incapable of outputting flood_arrival_time directly and low calculating efficiency of traditional manual method. This calculation method achieves automatically extraction with higher accuracy of flood_arrival_time by the utilization of loop filter algorithm.(2) The flood routing model of Luanhe right-bank flood protected zone is established. Firstly, a unified two-dimensional flood routing model is chosen to simulate flood routing of river and protected area considering the fact that Luan River is wide and shallow with double dike. Since the distribution patterns of roads and dikes in Luanhe right-bank flood protected zone are complicated, DIKE and GATE in MIKE21 FM are applied to deal with the water-blocking construction and dyke breaches based on the investigation of the key issues in modeling process. Finally, the model parameters are analyzed basing on the flood process of Luanxian station and Luanhe practical survey flood imprint materials in 2012. The results meet the basic requirements of flood hazard mapping.(3) Firstly, dyke breaches and simulation schemes are studied according to the requirements of flood hazard map making. Then simulation schemes are calculated by calibrated model. The rationality of the flood routing simulation results and the flood arrival time automatically extracted is analyzed by using the simulation result of YanshanQushou dyke-breach under 100-year design flood. Analysis results suggest that MIKE21 FM can be applied to flood routing simulation of Luanhe right-bank flood protected zone, and the automatic extracting method of flood arrival time can be used in flood hazard mapping owing to its higher efficiency and accuracy compared to manual method. The spatial expansion process of the submerged area and the flood inundated area are obtained by analyzing the single and multi-frequency flood hazard based on rationality analysis of simulation results, which provides a scientific basis for flood control, evacuation and disaster assessment of Luanhe right-bank flood protected area.