The Response Of Debris Flow To Climate Vertical Differentiation In The Upper Reaches Of Min River

The upper reaches of Min River is in the transitional zone from the Qinghai-Tibet Plateau to the Sichuan Basin.Together with the active seismic belt,the upper reaches of Min River has become a typical ecologically fragile area and a debris flow disaster-prone area,and the vertical zoning of the upper reaches of Min River is obvious and complete.Therefore,this thesis selects the regional vertical zone and debris flow as the analysis object,and uses MATLAB,ArcGIS and SPSS analysis software to analyze and compare the climatic characteristics and interannual variation trends of different climatic zones.The entropy weight method is used to evaluate the activity of debris flow in the upper reaches of Min River.Exploring the relationship between climate change and debris flow activity and using CCA model to quantitatively analyze the coupling relationship between the two.Based on the previous predictions of climate change in the upper reaches of Min River,the temporal and spatial trends of debris flow activity along the upper reaches of Min River with climate change in the next 30 years are obtained.The climatic vertical differentiation and its variation characteristics in the upper reaches of Min River are clarified,and the coupling relationship between vertical climatic differentiation and debris flow distribution are revealed.The main results are as follows:(1)Vertical differentiation characteristics of the upper reaches of Min RiverThe average annual temperature and evaporation in the upper reaches of Min River decreased with the increase of the elevation.The multi-year average relative humidity increased with the increase of the elevation and then increased.The average annual precipitation increased with the increase of the elevation and then decreased.The number of hours increases as altitude increases.The annual average temperature,annual precipitation and annual evaporation of the vertical zones of the upper reaches of Min River show an upward trend.The temperature rise rate of the whole basin is about 0.009 °C/a,and the annual precipitation change rate is about 3.12 mm/a.The rate is about 6.52mm/a;the average annual relative humidity and annual sunshine hours of each climate vertical zone show a downward trend.The relative humidity change rate of the whole basin is about-0.21%,and the annual sunshine hour change rate is about-9.82 h./a.(2)Debris flow distribution and activity characteristics in the upper reaches of Min RiverThe debris flow disasters in the area were mainly distributed along the main stream of the Min River.The debris flow ditch on the upper reaches of Min River is mainly distributed in the temperate zone and the cold temperate zone,accounting for 68.44% of the total number of debris flows.The types of debris flow activities are mainly Class 1 and Class 2.(3)Coupling characteristics of debris flow activity and vertical variation of climate in the upper reaches of Min RiverFirst,qualitative analysis of the distribution of debris flows on various climatic factors.Then the CCA analysis method was used to analyze the correlation between the climate impact factor and the debris flow activity.The maximum value of the correlation between the X group representing the vertical variation of the climate and the Y group representing the activity of the debris flow was 0.724,and the debris flow activity and climate were considered.Vertical differentiation has a high degree of connectivity,indicating a strong correlation between the two.From both qualitative and quantitative perspectives,it can be concluded that there is a certain response relationship between vertical climate differentiation and debris flow activities.(4)Response characteristics of debris flow activities in the upper reaches of Min River to climate changeIn the upper reaches of Min River,the activity index of debris flow in the seven climatic zones between 2017-2030 and 2017-2050 is increasing.The maximum percentage increase occurs in the warm temperate zone.The minimum percentage increase occurs in the cold zone.In the next 30 years,the upper reaches of Min River Debris flow activities will intensify and debris flow activity will be more frequent.