基于GIS的山洪灾情评估方法研究

AN INTEGRATION OF GIS AND ANALYTICAL MODELS FOR EVALUATION OF DISASTERS CAUSED BY MOUNTAIN TORRENTS

本文探讨了应用地理信息系统与分析模型相结合的方法评估山洪灾情的途径。山洪灾情评估的难点在于：因山洪速度快、冲击力大常规水文观测难以进行；同时又因山洪历时短暂和影响的空间尺度小，遥感方法难以取得足够的信息。通过建立基于ＧＩＳ的水沙行为模型，在计算机屏幕上再现洪水场景，输出洪水过程中流速、水深、含沙量等信息，结合承灾体承灾能力分析，使山洪灾情得以准确评估。本方法以孙胡沟１９６９年８月１０日发生的山洪为例进行验证，效果良好。

Mountain torrents is a kind of flash floods which bring about a great loss of life and damages of properties in mountainous area.in order to support decision making on disaster reduction and prevention,it is necessary for us to evaluate disasters of mountain torrents quickly and correctly. The difficulties in evaluating disasters of mountain torrents lie in the impossibility of hydrologic observation by conventional method because of the grest flowing velocity and washing force and the insufficiency of information got by remote sensing method because of the short duration of mountain torrents.In order to overcome such difficulties,a new method which is an integration of GIS an analytical models is explored in this paper.what we use is an external integration method,i.e.the analytical model is integrated with GIS system as an external procedure.In the process of evaluating disasters of mountain torrents,the role of GIS is to transform vector data into grid data and to query,access,display and analyse grid data;the role of analytical model is to simulate behaviors of water and sand within grid and among grid and to determine the disaster class for each grid.The procedure for evaluation of disasters caused by mountain torrents is as follows:firstly to establish a database including data collection,map digitization and input of tabular data;secondly,to analyse data including DEM analysis,analysis of drainage network and rastering;thirdly,to run the model which includes sekction of simulation parameters,simulation of flood and simulation of sand transprotation within the watershed;fourthly,to evaluate disasters which includes calculation of washing forces,analysis of disaster──bearing capacity and determination of disaster classes.Taking mountain torrents in the Sunhugou watershed on Aug.10,1969 as an example.we tested this methd.The result showes that integration of GIS and analytical mdel is an efficient method for evaluating disasters caused by mountain torrents.GIS promotes establishment of distributed hydrohgic model by management of spatial data; analytical model extends function of GIS by provision of hydrologic information such as water depth,flowing velocity and sedlment concentration.Compositeness of spatial ad temporal information in GIS is an important part in evaluating disasters caused by mountain torrents.Formation of disaster by mountain torrents is a dynamic process in which sufficient information can be got only by simulation of water and sand behaviors.Efficient management and output spatiotemporal information are a subject that need be further studied in GIS.