The Impact Of Changing Environment To The Flood And The Flood Warning Studies

Flood prevention and management has always been the focus of attention and discussion in many basins of our country and even in the world, also is the difficulty. In the backdrop of the global climate change, changing environment has become the primary causes which impact the floods happening and developing. Through the comprehensive analysis of the changing environment, understanding the effect relationship between the changing environment and flood, improving the precipitation flood forecast technique, evaluation of flood risk in a river basin, that can improve prediction of flood risk and judgment, consequently can take reasonable measures to deal with as soon as possible. But it is a complex and huge systemic problem to avoid flood risk and take care of all aspects of the flood disaster reasonably through scientific prediction method in a changing environment. To solve these problems, this article takes Fengman reservoir watershed upstream of the second Songhua river northeast of our country that is riched in water resource as the goal, comprehensive analyzes the changing imvironment of the basin and its' influence on the flood, study and put forwoards the risk controllable precipitation range forecasting method, constructing the Veriable set flood vulnerability assessment method and system based on the Variable sets. that can provide a scientific references in improving the basin flood control engineerings' planning and construction ability, can strengthen the precipitation forecast method cognitive ability, and is helpful to improve the application level in the reservoir flood control operation, thereby can ensure the society developing coordinately. The main research contents and results are summarized as follows:(1) Through Statistics, ArcGIS tools, the Variable Fuzzy evaluation and other methods analyzes the change of watershed underlying surface land use, hydraulic engineerings from two angles of qualitative and quantitative with the change of social and hydraulic infrastructure and so on. Results shows that the third zone (upstream of Baishan reservoir) forest coverage to keep for a long time in more than 80%, the second zone (upstream of Wudaogou) vegetation coverage rate has been below 20% low, overall land use change is not big, but does not exclude the large variation in the local areas; Regional population keeps stable, rapid economic development, infrastructure construction in constant speed; The change of the basin's hydraulic engineerings quantity and capacity is most obvious, small and medium-sized reservoir amounted to more than 10×108 m3, close to 10% of the total capacity of Fengman reservoir, the flood control capacity of 40% of its vast storage capacity can improve the flood control and its irrigation through flood water storage, but may also be because of too much water and engineering reasons such as collapse dam bring water to the downstream reservoir uncertainty, thus increasing the risk; By studying the changing environment, we can accomplish know fairly well and provide decision-making basis for reservoir operation and management.(2) Take primary cause of the changing environment, the hydraulic engineering, as the breakthrough point, Using lumped xin an jiang model and distributed HEC-HMS model to study the effect of hydraulic engineering for flood regulation. In xin an jiang mainly by adjusting the model parameters in the model to consider; the influence of hydraulic engineering Module in the HEC-HMS model by adding the reservoir, the partition all the reservoir on the sub basin reservoir is turned into a virtual polymerization, polymerization capacity of the reservoir physical properties and high dam according to the distribution characteristics of the subunits with unit length to determine the main channel and the longest river, false stator unit of rainfall runoff yield first after reservoir filling up the polymerization can be out of the stream to the downstream, the dam crest exactly the way of water research area actual operation status of the vast majority of small and medium-sized reservoirs.(3) Based on the Variable sets theory and it's basic theorems, raising the Variable sets flood vulnerability assessment method; In traditional evaluation indexes joined the reaction exposed to flooding people's psychology and behavior of the relevant indicators, and formed the comprehensive assessment index system. This paper discusses the development of Variable sets in detail elaborated the three basic theorem of Variable sets theory, put forward the Variable sets the flood vulnerability assessment method; In the common evaluation system, subsquently environment, hazard -formative factors bearing such clear deterministic index created on the basis of the affected population in face, the psychological bearing capacity and hazarding the emergency disaster relief capability of the local government this kind of fuzziness index, the fuzzy index quantitative calculation by means of equivalent transformation, finally get the comprehensive assessment index system. Using the proposed method to assess the application of Variable sets, the vulnerability level drawing of the basin, can provide useful information for basin flood warning and be helpful to make better decisions in flood management.(4) Raise an ensmble precipitation range prediction method based on the TIGGE data. Analyze the ultimate task and purpose of ensemble forecast thought, in view the defects in probability forecast and quantitative forecast of these ensemble forecast product usually adopted at present. Using the original forecast data of four climate centers ECMWF. NCEP, CMA and CMC provided by TIGGE, screen out the forecast range much closer to the measured value from the initial forecast range of the original data through the method of probability. The form of range forecast firstly is the quantitative results, no longer is the judgment on whether belongs to a certain scale of precipitation; Secondly, the range itself contains the error of the forecast uncertainty, thus in the applications of forecast product, we have sufficient time and space for prediction of risk and error into consideration, consequently the loss by the forecast uncertainty will be reduced and its advantages are obvious. From the application results in the study area, the results never worse than other forecasting methods not only in probability but also in quantitative, the effect in precipitation over the heavy level will be more clear.(5) On the basis of the ensemble rainfall range forecast, the pattern and effectiveness of rainfall forecast information used for the basin flood control early warning is studied. Incroporating the flood vulnerability and the warning information to further improve the reliability of the warning.Compared the early warning's difference of the traditional ensemble forecast result of the single valued average and control forecast and the range valued forecast result on the principle and method; Through statistical analysis of the rainfall-runoff data of the study area for many years, the flood control graded warning threshold standarded is divided into 5 levels and signed with color from blue to red; Using the results of the ensemble range rainfall forecasts to analyze the flood warning of the study area,and then based on the rainfall forecast and considering the environment change getting the flood forecast warning; Finaly combining the area vulnerability map to analyze the utility pattern of the warning information in different regions and the under the different earlier environment conditions.