... amount of initial rainfall and the measured value of Road surface runoff. According to Equation (1), rr was calculated as the slope of the regression equation of measured Road surface runoff and ... (g)Overflow runoff ratio,roJournal of Water and Environment Technology, Vol.3, No.2, 2005 - 269 - Figure 15. Overflow runoff ratio of load and flow Figure 16. Estimated and measured values of pollution ... data of change of pollutants in soil. Keywords Road surface runoff, soil purification facility, model INTRODUCTION Lake Biwa is the largest lake in Japan, and it covers 1/6 of land area...