| This paper analyzes the disaster factors of mountain torrents and discusses the influence of landslide sediment yield on flash flood in Southwest China.Firstly,the research status at home and abroad is integrated to clarify the important influence of landslide sediment yield in the numerical simulation process of flash flood disaster.Based on the existing research,a method for estimating the quantity of potential landslide material sources in a typical small watershed is established by using the landslide risk analysis model.The method is applied to the verification of four typical mountain torrents in the Longxi river basin.The results are compared with the remote sensing interpretation results and post disaster investigation reports to confirm the reliability of the method.At the same time,the landslide sediment yield of different small watershed in southwest mountainous area is estimated.According to the historical disaster data,the types of mountain torrent disasters under the influence of sediment supply in different basins are calculated.Finally,the estimated volume and its distribution of landslides are input into the Massflow model as the source distribution to simulate the impact of landslide sediment yield on the "6.26" flash flood disaster in Caogu river basin and analyze its disaster mechanism.The main achievements are as follows:(1)Based on the combination of slope-units and TRIGRS model,a method for estimating the potential source volume of landslide in watershed is proposed.In order to verify the reliability of the method,taking the "8.13" rainstorm event in Longxi river as the background,we calculated four typical mountain gullies in the Longxi river basin,and verified the method by comparing the results of the estimated results with the remote sensing interpretation results and the post disaster investigation reports.Through the treatment of slope-units,some scattered points without landslide are removed.The landslide group in the basin is also cut effectively,which reduces the influence of landslide group on the calculation results.Through field investigation and measurement,it is found that the soil water content changes with seasons in a year,and the rainfall in the early stage has a great influence on the change of soil water content.When the soil water content changes,the size and distribution of landslide will change accordingly.When the water content reaches 28%,landslides will occur with the increase of water content.(2)In order to explore the influence of landslide sediment supply on different watersheds in southwest mountainous area,the potential source of landslide was analyzed in four typical small watersheds,namely Baisha river,Wangmo river,Zhongdu river and Caogu river.Through the analysis of historical disaster data,the disaster types of disaster points in the basin are obtained.There are different types of mountain torrents in different basins.The simulation results show that the total amount of potential sources in different watersheds is quite different,and the potential source quantity has a great relationship with the geological conditions and slope gradient in the watershed.Most landslides developed in 20 °-50 ° on the slope angle of the mountain.Combined with historical mountain torrent disasters,it is found that the basins with large potential sources are seriously affected by sediment recharge.In the small watershed of mountainous area,due to the distribution of landslide and other material sources,river gradient and other factors,the types of flash flood disasters in different areas of the watershed are different.So it is necessary to set up different disaster prevention and early warning areas for different disaster prevention objects.(3)Taking "2020.6.26" flash flood disaster as the background,based on the obtained landslide source size and distribution results,as the source distribution input to Massflow model,We simulate the process of mountain torrent disaster in Caogu river.After field investigation,it is found that the simulation result is reliable.Through the numerical simulation results,it is found that under the supply of landslide sediment,the sediment will deposit in some areas due to the influence of topography and geomorphology,which will affect the flow path of the river.In landslide prone areas,the influence of sediment action on the disaster caused by mountain torrents should be considered in the numerical simulation of the basin. |
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