SIMPLIFIED ESTIMATION OF SOIL MOISTURE BEHAVIOR DUE TO RAINFALL INFILTRATION IN RIVER LEVEE SLOPES USING EFFECTIVE RAINFALL

Abstract

 A simple method for estimating soil moisture behavior in levee surfaces due to rainfall infiltration was studied using time series of effective rainfall calculated based on hourly rainfall. The similarity between the soil moisture behavior and the time series of effective rainfall was evaluated for 128 rainfall cases measured on the back slope of a first-class river levee, and the half-life of the effective rainfall with the highest correlation coefficient was calculated as the optimum half-life. Short-term and long-term optimum half-lives, which are specific to the levee surface in question, are proposed as short-term and long-term extremes of the optimum half-life. The similarity between the time series of effective rainfall and soil moisture behavior using these optimal half-lives was confirmed for rainfall cases with different cumulative rainfall and maximum hourly rainfall, and the usefulness of effective rainfall as a rainfall indicator for estimating soil moisture behavior in the levee surface was discussed.