In order to predict the site at risk for the occurrence of sediment-related disaster, the author has developed a system in which the value of rainfall index R’ can automatically be calculated and the calculated results are represented as a contour map with interpolated information between AMeDAS stations. Verifying whether the R’ value that calculated in real time using only AMeDAS data has a correlation with the timing and the place of sediment-related disasters occurred caused by the heavy rainfall in July, 2018, it was shown that the contour map of R’ value is sufficiently effective for the prediction of“ time” and“ place” where sediment-related disasters would occur. Under existing circumstances, however, from the viewpoint of the guideline of evacuation, it should be emphasized that we have only a few minutes to judge the danger of landslide disaster on the basis of R’ value alone..