Discuss on the correlations between landslides and rainfall and threshold for landslide early-warning and prediction

Historical data of rainfall and landslides in Shenzhen City are researched in detail. And the partial correlation between landslides and rainfall, the correlation between landslides and rainfall intensity, and the statistic relation between landslide and rainfall time are analyzed. The results show that: First, the partial correlation coefficient is better between landslide and the two-days rainfall, and the sum of rainfall. It is clear that the regional landslides will appear when the rainfall reaches some numerical values. Second, the relation is very strong between rainstorm and landslides; the correlation coefficient is beyond 0.8, especially the great rainstorm and the unusual rainstorm. They can trigger landslides. Third, the occurrence time of landslide is parallelism to the rainfall season, the more is rainfall, the more is landslide. In addition, the occurrence time of landslide accords with or lags behind that of rainfall and rainstorm; but the lagged time is less than four days, and the landslide probably arises in the same day and the second day when the rainstorm takes place. The threshold values of critical rainfall and critical rainfall intensity are discussed. At the last, the indexes and grades of spatial early-warning are taken by the coupling between the model of landslide hazards and rainfall so that it predicts the time and space that the landslides occur.