A Study On GIS-Based Hazard Assessment About Geological Hazard Of Dazhai Gully And Haizi Gully In Baihetan Reservior

Four step-hydropower stations have been planned to be constructed on the lower reaches of the Jinsha River .from Panzhihua to Yibin, which are essential to electricity transmission from west to east, and also to the development of the west China. Baihetan hydropower station will be constructed within Baihetan valley which links Qiaojia County of Yunnan Province and Ningnan County of Sichuan Province. Geological hazard (especially debris flows), however , is active in this valley, a great threat to the construction of hydropower station there. Among the 130 debris flow valleys, Dazhai Gully suspends high on the up range of Baihetan hydropower station , with an altitude over 970m and a drop more than 350m. Gravels , mud and flood in this valley brings the construction site in great danger. 3 kilometers upriver from the mouth of Dazhai Gully , lies the Haizi Gully ,which is also frequented by debris flows, but will be taken as the dumping site for the construction. The Latent geological disaster poses a serious threat to the engineering construction, so it is imperative to assess rightly about the geological hazard in the tow gullies , estimate their development and make the cure programe reasonably and design the cure projection so as to safely put into construction the hydropower station and the sites needed.The risk on geological hazard is a mark of degree about activity on geological hazard , the main content of hazard assessment about geological hazard is assessing the degree activity of geological hazard and reflecting the ability of break . The hazard assessment about geological hazard can avoid or reduce the influence of various latent disaster and induct;can avoid the disaster region to the expensive processing expenses and a huge sum of surcharges in various engineering activity;can with utmost promote and keep the coordination of the environment and development, so carrying on risk assessment about geological has profound realistic meaning.This paper takes it that be as low as the influence on hydropower station lowest as the point of the departure, which to choose the study on risk assessment on debris flow as the main subject. At the base of analyzing the forming condition and the activity, leading GIS to the hazard assessment about debris flow.The spatial pictures involved in this paper include geography diagram which scale is 1:50000 , and thedistributing map of overlying material that is closed related with the formation of debris flow and the geological map and so on. The appropriate appraise indexes were selected and analyzed carefully by using ArcGIS8.3 program, and were showed with GIS in the form of figure, picture, then this paper utilized strong space of GIS software(ArcGIS) to analyse the function, through raster calculation various kinds of appraisal indexes were added on one picture , according to the analyzed result, the digital model of risk assessment of debris flow was built and the risked assessment chart of debris flow in the tow valleys was obtain, at last completed carefully the risk assessment of Dazhai Gully and Haizi Gully debris flows. The analyzed results basically reflect the debris flow nature.Though the present assessment of the risk on Dazhai Gully and Haizi Gully debris flows, this paper got the influence degree of the electricity station, and according to the assessment result adopt scientific manage measure and the monitor forecast, carry out reasonable prevention and cure of debris flow, so the hydropower station project will be carry out successfully.It is proved by practice that in comparison with the hazard assessment of the geological hazard based on paper map, the GIS-based hazard assessment of the geological hazard is faster and more effective. Coordinating with appropriate assessment model it can be replace the traditional method of hazard assessment so as to improve the efficiency and the accuracy of hazard assessment of geographical hazards. The result shows that the combination of information value model and GIS id effective in assessment of geological hazards risk. Then, the hazard assessment of geographical hazards advance further in modelized, quantified and modernized direction.