Study On Risk Zoning And Safe Use Of Flooded Area Land In Lower Beaches Of The Weihe River

The frequent flood and unreasonable land use deteriorate the land use risk problem in the flooded area of the lower reaches of the Weihe River, which cumbers the economy development of this area. Basing on the theory and the methods in the risk science, the response mechanism between land use and flood was established by bridging the relationship between changes of the traditional land use and disaster reduction. By analyzing the characteristics of the land use and the evolution of the flood in recent ten years, and evaluating the land risk and land zoning, some important suggestions to many related aspects such as adjustment to land use structure, reformation to the environment resulted from disaster, et al., have been put forward. Main results are as follows.(1) Land use change, floodwater and watercourse variance are all the important factors of land risk because of the special location of the flooded area.(2) Areas of construction land, grassland, pickled land, naked land, forest and garden are increasing, while the area of agriculture and water land are declining. In particular, 2.08 km2 agriculture and 0.94 km2grassland have been undergone pickling, and 3.47 km2 water area have been converted into pickled land as the decrease of runoff. The connectivity of dominated patches is declining gradually, and its fragmentation and heterogeneity are in the decreased. The fragmentation and heterogeneity of agriculture and forest are both on the decline, while construction land is increasing. All indexes of grassland, pickled land and water area fluctuate dramatically.(3) The flood evolution process in the lower reaches of the Weihe River is simulated by means of the Saint-Venant equation, and some main factors including submerge region, water depth, duration and flowvelocity were obtained. The error between computation data and the data come from survey is small, which shows that the choice to parameters are reasonable. The range and depth of the submerge area, the duration of the flowing velocity, and the radio of increasing speed of the flood were obtained by simulating and computing to four types of the flood flowing process with different frequencies. By comparing the date above mentioned to the data provided by the Yellow River committee and Department of Water Resources of Shaanxi Province, the higher probability of this result was verified.(4) According to the statistical data of population, society, and economy, some different risk areas are zoned, which shows that the area are becoming bigger in the order of extra serious disaster zone, serious disaster zone, disaster zone, safe zone. The exterior bound of safe zone, disaster zone and serious disaster zone, extra serious disaster zone of a-hundred-year-return-period is farther than that of a-fifty-year-return-period. When the characteristics are same, the loss of the land risk expectation is bigger in the same lattice.(5) Some reasonable ways to guarantee the safe land use were put forward, which suggests that regulating ways of land use, controlling Tongguan elevation, change Beiluo River's course and floodwater utilization are necessary..