Numerical Simulation Of Changbaishan Tianchi Outburst Flood By Digital Elevation Model

Volcanic hazard is one of the major natural disasters, due to its horrific destructiveness, wide spread range, long continuance and serious losses. Changbaishan Tianchi volcano has erupted many times in history. Monitoring data show that deformation of volcanic cone is occurring and magma is still in the active state right now. It’s said that eruption of the Tianchi volcano (1199-1200) is one of the fiercest in the word in the past 2000 years. Recently, as human awareness of disaster prevention and mitigation growing, the security of Tianchi volcanic area is brought into routine. The volcanic lake, which owns massive weight of water, is a major consideration when it comes to the disaster prevention and reduction of Tianchi region. Once it breaks out, the volcanic lake will collapse instantaneously, life and property of Hundreds of thousands in the Erdaobaihe district will be in danger.This thesis is supported by the project of "Hazard prevention and subject plan of Changbaishan Tianchi volcano", which is done by a collaborative effort between Jilin Earthquake Administration and Urban and Engineering Management Information Lab of OUC.I am responsible for the "Numerical simulation of three kinds of fluid hazards of Changbaishan Tianchi volcano" in this project, from which the flood hazards is selected as the major analysis object in this thesis, the research process and results are as follows:(1) The DEM(Digital Evaluation Model) of research area is generated via the 3D analyst tools in ArcGIS based on the vector contours and evaluation points around Tianchi, then 3D model is built and converted into terrain file by 3ds Max, and finally a non-defective STL file is produced after amended by FLOW 3D.(2) Cone model of Tianchi is built combine with the mature computing method of maximum discharge of dam break water flow in the dam site, the quartic curve fitting and the realistic data of Tianchi volcanic lake. And then the dam-break model of Tianchi is established, from which, the flow data needed by the fluid flow simulation in FLOW 3D is computed.(3) Structured grid model of the research area is established in FLOW 3D according to the STL file generated before. Model parameters, boundary conditions and initial conditions are imported into the computer, which are based on the actual geographic data collected. Finally, thousands of images which are valuable to the conclusions are exported after the simulation in accordance with the condition Ⅰ, Ⅱ and Ⅲ. When condition Ⅰ happens, the water level of the Tianchi lake rises by 0.159km, and all of the water will escape; when condition Ⅱ happens, the water level rises by 0.086km, and half of the water will escape; when condition Ⅲhappens, the water level rises by 0.046km, and a quarter of the water will escape.(4) Two kinds of data are picked from the outputs of condition Ⅰ, Ⅱ and Ⅲ, from which 102 images are selected respectively in equal intervals of time. All of images are compounded by ArcMap, and administrative divisions, residential areas, main rivers as well as hydrographic net around research area are also overlaid with the images,6 flood disaster maps are generated by ArcMap. Inundated characteristics of the condition Ⅰ, Ⅱ and Ⅲ are analyzed as follows:① If condition Ⅰ happens instantaneously, the maximum velocity of water head surpasses 25m/s, maximum water depth is 20m at least.10 minutes later, flood invades into the watercourse of Sandaobaihe after traverses the Erdaobaihe, and then inundates the Huangsongpu tress farm, the inundated area is distributed as a sector overall; After 45 minutes, flood arrives at Erdaobaihe Town in the speed of 5-10m/s(10-15m/s in some region). As a result, Nature Conservancy of Changbaishan and villages such as Erdao, Tiebei, Hongfeng, Changsheng, Toudaobaihe, Baihegang, Shuitian, and etc.are submerged, where 1-3m of water depth has. The Xiangyang and Sihe village, which are located between Erdaobaihe and Sandaobaihe, will be also under water, where the water depth is less than 1 meter and the speed is less than 5m/s.② If condition Ⅱ happens instantaneously, the maximum velocity of water head surpasses 20m/s, maximum water depth is 20m at least. After 1hour and 15 minutes, flood arrives at Erdaobaihe Town in the speed of 5-10m/s, Nature Conservancy of Changbaishan and villages such as Erdao,Tiebei, Hongfeng, Baoma, etc. are submerged partly, where have 1-3m of water depth. After1.5 hours, villages such as Changsheng, Shuitian, Toudaobaihe and Baihegang are inundated. The district which is 2-6km west of Erdaobaihe is submerged. Areas including Hongfeng village which are located between Erdaobaihe and Sandaobaihe, will be also under water, where the water depth is less than1-3m.③ If conditionⅢ happens instantaneously, the maximum velocity of water head surpasses 20m/s, maximum water depth is 15m at least. After 20-30 minutes, the inundated areas distribute as a small sector, which skews slightly to the northeast. Water will traverses the watercourse of Erdaobaihe, then over brims the Sandaobaihe, regions less than 3km east to the Sandaobaihe is inundated, where the speed is less than 5m/s, and the maximum water depth is 3-5m due to the ravines.1.5-2 hours later, flood traverses the watercourse of Erdaobaihe once again, and access the watercourse of Sandaobaihe after submerging the most part of Hongfeng village, where the speed reduces to less than 5m/s and water depth is less than lm.(5) Finally, combined with the maps of flood distribution and flood characteristics under condition Ⅰ, Ⅱ and Ⅲ, some Disaster prevention protection recommendations about the outburst flood are put forward, according to the flood control map and relevant reservoir data supplied by Water Conservancy Bureau of jilin province.