Abstract
The purpose of this study is to clarify the effect of uncertainty in the rainfall-runoff process. Though we have performed runoff analysis deterministically in the past, the uncertainty in the rainfall-runoff process is quantified stochastically through the introduction of the theory of stochastic process. We purpose the theoretical framework to evaluate the uncertainties using the relationship among Langevin equation, stochastic differential equation (SDE) and Fokker-Planck equation (FPE), because the lumped rainfall-runoff model is described by ordinary differential equation. That is, it is attributed to the similarity of structure between the lumped model and Langevin eq. or SDE. As a result, we provide a new perception into decision-maker in flood. Moreover, we theorize a new framework regarding reliability analysis with the distribution of water level as external force and the failure probability of levee as resistance.
