In this study, We proposed a method to estimate the design flood by area ratio in an ungauged basin. For that, the discharge
parameters was determined by calibration of observed data at the watershed outlet and then peak flow was estimated by
area ratio. In order to verify suggested method, peak flow was compared the observed discharge of the small river basin and
the design flood discharge of river implementation projects. The results were summarized as follows. As a result of
comparing the discharge by the area ratio and observed discharge, the difference of peak flows were analysed 14 ~ 25%.
When the discharge calculated with area ratio of small river was compared with the design flood discharge of river
implementation projects, the relative error was analyzed to be less than 20%. It means that suggested method in this study is
appropriate.