Study On The Early Warning Model Of "7.25" Mass Rainfall Landslide Disaster In Tianshui City

The emergence of extreme rainfall is often accompanied by the occurrence of large-scale regional geological disasters.In order to reduce the losses caused by disasters,it is particularly important to study and predict regional mass landslides caused by extreme rainfall.In this paper,Tianshui extreme rainfall disaster event on July 25,2013 was taken as an example to study its susceptibility zonalization,disaster distribution,the relationship between landslide and rainfall and the rainfall threshold of mass landslides,and build the meteorological warning model of landslide disaster in this area.The main results are as follows:(1)The study area is divided into four landslide prone areas by using information volume model,among which the extremely low prone area accounts for 0.75% of the total area,the low prone area accounts for 49.18%,the middle prone area accounts for 30.13% of the total area,and the high prone area accounts for 19.94% of the total area;(2)Using post-disaster images for landslide interpretation work,the results show that the mass landslides are concentrated in the central area in the horizontal direction,and mainly distributed between the altitude of 1650m-1680 m in the vertical direction;(3)The effects of the four rainfall processes on the spatial distribution of the landslide are the preparation for the first rainfall,the decisive role of the second rainfall,the propelling role of the third rainfall and the disaster-causing role of the fourth rainfall;(4)The results show that the minimum critical rainfall of hourly rainfall,heavy rainfall and accumulated rainfall are 17.5mm,105 mm and 250 mm respectively,in which the hourly rainfall and short-term heavy rainfall in the range of 17.5mm-20 mm and 105mm-120 mm are the prone areas of mass landslides.The statistical results are consistent with the prediction results of I-D threshold curve of the whole study area and different prone areas;(5)Based on the logistic regression analysis model,the early warning model of rainfall type mass landslides in Qinzhou District of Tianshui city is constructed.The results show that 76.29%,70.85% and 39.71% of the 350 disaster points in Jintai District of Baoji City have reached the three-level warning level,two-level warning level and one-level warning level,respectively.On this basis,the verification of 200 densely developed disaster points shows that there are 135 densely developed disasters,about 65%,The results show that the model has a good warning effect on mass landslides.