湖南省山丘区小流域山洪灾害危险性评价

本文采用信息量模型法研究湖南省山丘区小流域山洪灾害的危险性程度。信息量模型的最大意义是能从影响山洪灾害发生的众多因素中找到“最佳因素组合”。基于湖南省1955-2015年近60年的历史山洪灾害数据,结合地形、下垫面以及降雨条件,利用信息量模型按危险性程度高低划分出湖南省山丘区山洪灾害危险性的分布情况。研究结果表明,湖南省山丘区山洪灾害容易发生在坡度小于10°,高程小于100 m,起伏度小于30 m,土地覆被为人工表面,土壤类型为粘土以及降雨量在1584.3~1662.0 mm之间的区域。湖南省山丘区危险等级较高的地级市有永州市、郴州市、株洲市、岳阳市、娄底市以及长沙东部山区,经过混淆矩阵验证后,通过信息量方法建立的山洪灾害危险性评价模型准确率为75.36%,基本可信。

Hazard Assessment of Mountain Torrent Disaster in Small Watersheds of the Hilly Areas of Hunan Province

In this paper, we use the information volume model to study the hazard degree of mountain torrent disaster in hilly area of Hunan province. The greatest significance of the information volume model is that it can find the best combination of factors from various factors that affect the occurrence of mountain torrents. Hunan Province is one of the most serious mountain torrent disaster provinces in China. In order to study its hazard degree of the mountain torrent disaster, we divide Hunan Province into several small watersheds to evaluate the hazard of mountain torrent disaster using the data of historical flash flood disaster points spanning years from 1955 to 2015. Information volume model was established to calculate the information of the six factors: elevation, slope, relief, land cover, soil types and rainfall, respectively from the consideration of three aspects including the terrain, the underlying surface and the rainfall. The information volume of six factors were calculated, respectively. Based on the value of information volume of these factors, we obtained the combination of factors with the biggest influence of flash flood disasters. Through calculating the total value of information volume for all small watersheds in hilly areas of Hunan Province, we classified the information volume into five types associated with different dangerous levels. The results show that: the most significant contribution to the flash flood is the artificial surface of land cover type, with a information volume of 1.771, followed by the types with relief degree less than 30 m as well as the clay soil type (both at a value of 1.331). The mountainous torrent disaster for Hunan hilly area are likely occurred in areas with slope lower than 10°, elevation lower than 100 m, relief lower than 30 m, of which the land cover is artificial surface, the soil type is clay and annual mean rainfall is between 1584.3~1662.0 mm. Statistics of each level of dangerous areas show that the second-high and the third-high hazard types have the largest area in the mountain areas of Hunan, accounting for 26.59% and 26.63%of the total mountain areas, respectively. Area percentage of the fourth-high risk type is 20.89%, and that of the first and fifth-high hazard types is 13.89% and 11.99% respectively. In the hilly areas of Hunan province, cities with higher hazard levels are Yongzhou City, Chenzhou City, Zhuzhou City, Yueyang City, Loudi City and the eastern part of Changsha. In this study, 90% of the mountain torrents (1243 mountain torrents) were selected randomly from 1381 mountain torrents disaster spots in Hunan Province, and 10% of them were used to verify the hazard assessment results. The verification of confusion matrix demonstrated that the accuracy rate of this model is 75.36%, indicating a basically credible results of the spatial distribution of hazard degree estimated in this study. The mountain torrent disaster system established in this study still needs to be improved. The selection of factors and models, as well as the quantification of human activity factors should be considered in the further study.