This study discusses the basic problems for estimating the change of the hydrological characteristics through the transform of land use caused by the land reclamation in a hilly watershed.
First，a detail watershed model for applying the kinematic runoff model such as overland flow type is constructed in the Uchida hilly watershed of 0.107<km>^^^2, the 30% of which is developed to the grazing area byland reclamation Second, the effective rainfall is calculated by Kadoya's new method using the relation between cumulated and reserved rainfall curves. Third, the equivalent roughness N or slope flow constant k which are parameters of overland flow model are estimated as the uinform value for a watershed model or each value for a hilly and grazing watershed model. Fourth, the applicability of overland flow model is examined by applying their optimum model parameters in the Uchida basin model. And it is found that the calculated hydrographs using the values of optimum model paralmeters are a fairly good approximation to the observed hydrograph in a large flood runoff. However, the practical method for the estmation of effective rainfall in the each block of land use is the subject for a future study. Moreover, it is pointed out that the practical method of evaluation for the relation between the nonlinear runoff phenomena and the sequence characteristics of short time rainfall is to be investigated in the basin through the transform of land use by the land reclamation in a hilly watershed.