The flash flood is characterized as flood leading to damage by heavy rainfall occurred in steep slope and
impervious area with short duration. Flash flood occurs when rainfall exceeds Flash Flood Guidance(FFG). So, the
accurate estimation of FFG will be helpful in flash flood forecasting and warning system. Say, if we can reduce the
uncertainty of rainfall-runoff relationship, FFG can be estimated more accurately. However, since the rainfall-runoff
models have their own parameter characteristics, the uncertainty of FFG will depend upon the selection of
rainfall-runoff model. This study used four rainfall-runoff models of HEC-HMS model, Storage Function model,
SSARR model and TANK model for the estimation of models\' uncertainties by using Monte Carlo simulation. Then,
we derived the confidence limits of rainfall-runoff relationship by four models on 95%-confidence level.
Keywords : Flash Flood Guidance, rainfall-runoff model, uncertainty, Monte Carlo Simulation