杭州市暴雨洪涝灾害风险区划

暴雨洪涝灾害是一个多因素耦合的复杂系统，在自然灾害系统理论基础上，根据杭州市1959～2009年的降水资料、自然环境以及社会经济要素，综合致灾因子、孕灾环境、承灾体以及防灾减灾能力，构建区域暴雨洪涝灾害风险评价模型。考虑到降水、地形、水系以及GDP和耕地等因子，通过ArcGIS空间分析技术结合模糊综合评价法，编制以100 m×100 m栅格为基本评价单元的杭州市暴雨洪涝灾害风险区划图。区划结果表明杭州暴雨洪涝风险东北部高于西南部。杭州暴雨洪涝风险高值区主要在杭州市区、余杭区、临安市、富阳市和桐庐县的富春江流域、淳安千岛湖西南部地区。暴雨洪涝风险高值区主要集中在山谷、河边、江边、人口密集地区等区域

ECOLOGIC WATER TRANSFUSION IN THE LOWER REACHES OF THE TARIM RIVER BASED ON CBERS/CCD IMAGE

Based on the ecological water transfusion data from the Bureau of Tarim River Administration and Management (TRAM),the information about the time of conveyance,duration,water volume and arrival were collected to analyze the processes and impacts of ecological water transfusion in the lower reaches of the Tarim River.Using CBERS/CCD remote sensing images (195 m spatial resolution) during 2000-2007,actual river channel inundated with water and water accumulated areas including the length and width of the water surface were extracted by photo interpretation and digital image analysis.The information was then associated with water transfusion data and used to monitor ecological water transfusion situation.The results show that the length of river channel inundated with water was 51413 km,and the width of average river channel was about 4223 m.Compared with field investigations,the accuracy of the results derived from remote sensing images was 975%.The relationship between water channel width and ecological water transfusion volume was positively correlated.The maximum river channel width was more than 50 m,which appeared in 2003 because of the maximum ecological water transfusion.However, the minimum river channel width was only 2898 m in 2000 due to the minimum amount of ecological water transfusion."Overflow" type of ecological water transfusion had been adopted by the TRAM.As the result,rather amount of water had been accumulated in the lowlands from the Daxihaizi Reservoir to Kardy.It was closely related to the ecological water volume and the distance from the reservoir.The total number of flow accumulated areas between the Daxihaizi Reservoir and Kardy reached to the 153 from 2000 to 2007,and the area was about 1987 km2.In contrast,the number of flow accumulated areas was counted as only 43 from Kardy to the Tetima Lake,with an area of 832 km2.Overall,the results of remote sensing observation were in accordance with field measurements.However,there was certain uncertainty in our results,which might be associated with the quality of remote sensing images and the time differences between the exact time of water transfusion took place and the images were collected.We conclude that the remote sensing,Geography Information System (GIS),and Global Position System (GPS) may provide an accurate and convenient method to detect the ecological water transfusion process