Evaluation of Flood Risk of Jialing River in Beibei Basing on GIS
|Keywords||Flood Risk Evaluation Loss Ratio GIS Spatial Analyst BeiBei JiaLing River|
Flood hazard is one of the main natural hazards in our country and around world. Valley of important rivers in our country are subjected to flood and are caused huge losses. People are seeking the way of flood control since antiquity for reducing the flood losses. But we could find that there were not goog result if flood was contryed only by engineering ways from historical experience. The way of risk analysis was used in flood analysis and produced goog results following it used widely.The Jialing river which’s annual runoff amount is between 35.9 billion to 103 billion m3 is the first major tributary of the Yangtze river. The Jialing river’s annual runoff amount is 1/13 of the Yangtze upriver’s annual runoff amount.The jialing river water is abundant. Once the Jialing river upstream is flooding, Beibei must be affected because of Beibei in the Jialing river’s downstream. Beibei is one of nine main urban areas of Chongqing, and is important industrial base in Chongqing. If the flood of beibei suffer larger, which produces loss will be enormous. Through the analysis of this paper, it is known that the economic losses may be 3.16 billion Yuan if Beibei was suffered 100 years of the worst flooding.So the jialing river flood study in Beibei is very necessary.This paper mainly has the structure of six parts:The first part is the introduction. This part of the article is to show how the expatiates the background, and then summarizes the domestic research about floods, and finally points out the significance and research purposes.The second part is general situation of the study area and the data to prepare.This section describes the natural and economic conditions in beibei, the basic situation and the history of the flooding about the Jialing river, then explaines the data sources and processing. At last, the paper introduces the method of this paper-space superposition analysis. The third part is the hazard analysis evaluation in the study area.This part first introduces the meaning of flood and flood risk indicators of risk analysis, and points out the submerged depth as the major indexes of the flood risk analysis. Then it introduces the calculation method of submerged depth and submerged range, and finally evaluates the flood risk’s level. To calculate submerged depth and submerged range, the author simulates the different frequency of flood flood faceaccording to different frequency of flood of design flood. Using the flood generated face minus the DEM terrain data, we can get submerged depth and scope of submerged. As in the analysis of no account of the regional terrain connectivity, so we must do connectivity analysis about the result, it is often said that active submerged analysis. Considering the specific situation, this article will flood risk for a category 4, submerged depth in 0.5 m the following, for low risk; In 0.5～1.5m, for in danger; In 1.5～4 m, to a higher risk; In 4 m or more, for high risk.The fourth part is the flood vulnerability analysis and evaluation in the study area.This part introduced the meaning of the vulnerability, the hazard-affected body satellite image interpretation and interpret the results steps, the determination of the loss rate and vulnerability assessment results.This paper points out that the vulnerability evaluation index for the size of the loss ratio.The fifth part is the flood risk evaluation in the study area.This section describes the different land types of value estimation, in different frequency under the flood of of all kinds of hazard-affected body loss, and finally made a flood risk evaluation. The flood risk evaluation index is unit area in the possible loss value.Flood risk is divided into four levels. The loss value per unit area in 50 yuan/m2 below, the flood risk for low risk; In the 50～200 yuan/m2, the risk of flooding to risk; In 200-1000 yuan/m2, flood risk to a higher risk; In 1000 yuan/m2, flood risk for high risk.The sixth part is the conclusion and shortage.There were the main conclusions are of the article:(1) in developing the flood control work, Dongyang streets, Chengjiang town, Shuitu town, Caijia town, Shijialiang town and LongFengQiao streets are key fortification areaes. (2) In flood control work the government must pay attention to increase of urban residents and businesses in the propaganda of flood control and improve the urban residents and businesses of consciousness on disaster prevention and mitigation. (3) to strengthen the commercial, industrial and mining, such as multilayer residence hazard-affected body work of flood control. (4)Analysising multilayer residence, the author according to the area and the characteristics of the multilayer residence, puts forward the multilayer residence of each layer as an independent hazard-affected body, according to the different frequency of flood may be submerged depth, sure each plot in different frequency of flood may drown depth, and then plots may determine the flooded several floors, and will be submerged in the different households as a total floor hazard-affected body.