Abstract: The aim of this research is to offer theoretical basis for forecasting and warning single-ditch debris flow in the mountainous area of Beijing.Factors such as topography,geology,and rainfall that induce debris flow were analyzed in line with the formation mechanism of debris flow based on literature review in recent decade and rainfall data.The model P=RT^0.2/G^0.5 was adopted for forecasting single-ditch debris flow in the mountainous area of Beijing,and the warning models and corresponding thresholds for blue,yellow,orange and red warning levels were obtained and further applied to forecasting the debris flow in Longtan gully for verification.Results demonstrated that the forecasting model in the present paper could well predict short-term debris flow and acquire the susceptibility of debris flow in different time periods according to rainfall changes.The model can be taken as a scientific and effective method for rapidly identifying the susceptibility level of debris flow in the mountainous area of Beijing.

Key words: debris flow, prediction model, runoff mechanism, mountainous area in Beijing, single-ditch