COEFFICIENTS OF FLOAT IN ACTUAL RIVERS UNDER FLOODING CONDITIONS

Abstract

  We collected a large number of field data for the vertical velocity profile, measured with acoustic Doppler instruments like ADCP, under flooding conditions in large actual rivers and then compared the observed results for the vertical velocity profile and the coefficients of float with classical well-known theories and empirical formulas to evaluate the accuracy of the coefficients of float, which are the ratio of the depth-averaged velocity to the surface-layer velocity measured by floats. The observed velocity distributions and coefficients of float were in better agreement with the logarithmic velocity profile than Aki’s theoretical formula. Due to these results, the coefficients of float generally used in Japan, which are evaluated in line with Aki’s theoretical formula, were larger than the coefficients of float calculated by the measured velocity distributions. Based on these findings, we proposed how to evaluate the coefficients of float.