Study On Debris Flow Warning In Mountainous Areas Of Beijing

The debris flow disaster is the geological disaster that caused the most casualties in Beijing.Since the founding of New China,the debris flow has caused more than 500deaths and direct losses of up to hundreds of millions of yuan.In July 21,2012,the mountainous area of Beijing caused heavy debris flows caused by heavy rainfall,causing heavy casualties and property losses.There were more than 40 valleys in the area.Based on the study of debris flow warning in Beijing mountain area,it can provide targeted forecast and warning information for the threatened target.Therefore,regional debris flow prediction and early warning research has great academic significance and practical value.In this paper,the debris flow disaster of"7.21"in Beijing was taken as an example,and 40 debris flows in the research area were collected as research objects.Meanwhile,15 debris flow events occurred in other time periods were also collected.Finally,the warning model was applied to 311 debris flow channels in the mountainous area of Beijing,which directly threatened the safety of residents.The main conclusions are as follows:?1?In the"7.21"debris flow event in the mountainous area of Beijing,the main source of material came from the previous landslide and the collapse accumulation in the main channel.The formation mechanism of debris flow is that under the action of heavy rainfall,the surface runoff scours the loose solid material in the gully,and then the bottom is moved to mix with the water flow to form debris flow.Therefore,the influence of rainfall factors on it is very important.?2?Short duration heavy rainfall has an important influence on the development of debris flow of gully bed starting type.The investigation shows that on July 21,2012,a huge mudslide occurred in Beijing,among which there were many debris flows in Fangshan District where the rainstorm center is located.In addition,the rainfall duration of the induced debris flow in the study area was all within 9h,most of which were more than 30mm in the first 1h before the debris flow broke out,and most of which were more than 150mm in the early accumulated rainfall.?3?In this paper,Yu Bin's debris flow prediction model of gully bed Incipient Type:P=(RT^0.2)/G^0.5,combined with the incipient mechanism of debris flow in mountainous areas of Beijing,is selected for early warning,and good results are obtained.The 1-hour rainfall prediction model(C_r1=0.28,C_r2=0.35 and C_r3=0.47)and the 10-min rainfall prediction model(c_r1=0.062,c_r2=0.078 and c_r3=0.103)as well as their critical values are applicable to the blue,yellow,orange and red IV warnings of debris flow disaster in the mountainous area of Beijing.?4?The debris flow warning model:P=(RT^0.2)/G^0.5rainfall model and 10 min rainfall model applied to 311 potential debris flow valleys in Beijing mountain area,The critical rainfall factor parameter?R?corresponding to debris flow gullies is calculated,which can provide some reference value for the research of debris flow disaster prevention and control in this area,and can guarantee the property safety of local residents to a certain extent.