Study on the time conversion method of early warning indicators of flash flood disaster: a case of Qufu City, Shandong Province

To solve the problem of imperfect flash flood warning indicators in mountainous watersheds, this study proposes a conversion method of critical rainfall for different warning periods on the basis of the existing stormwater calculation formulae and applies it to typical mountainous watersheds. The specific method is to use the multiplicative power function method to interpolate and extend the early warning indicators of other time periods through the known early warning indicators of some time periods, apply them to Hengmiao Village and Gaolou Village, typical disaster prevention objects in Qufu City, Shandong Province, China, and verify the rationality of the results. The results show that the multiplicative power function method interpolates and extends the early warning indexes of 0.5, 1, 3, 6, 12, and 24 h under the same soil moisture condition. Based on the historical actual mountain flood disaster rainfall, the correlation coefficient R-2 and Nash coefficient Ens are calculated to be 0.85 and 0.86, respectively, which verifies the applicability of this method. This study provides a convenient and quick way to unify the time series of regional early warning indicators and a feasible way for other regions to study regional overall early warning.