Drainage Coefficient

For proper drainage, it is necessary to know the desirable drainage rate (drainage coefficient), which depends on the rainfall intensity and amount of surface water admitted to drainage system. Direct measurement of drainage coefficient is location specific and difficult for large areas hence an indirect method of its estimation using rainfall analysis is the most suitable approach. The relative performance of 4 probability distributions with respect to Weibull¿s plotting position method applied to estimate 1 to 5 consecutive days maximum rainfall has been studied to understand the behavior of these distributions and to assess the reliability of design rainfall corresponding to various return period. Normal distribution with lowest Chi-square value found to be best probability distribution in predicting 1 to 5 consecutive days maximum rainfall for Parbhani.