A method for establishing stage-discharge curve (H-Q curve) using a runoff model to the rainfall observed in a basin and the water level observed in a river channel was discussed. A quadratic function that represented the relation between water level and discharge was built into the runoff model. When the observed water level hydrographs at some floods were reproduced, the H-Q curve was obtained. The method was applied to six water level stations in Shikoku which observed runoff quantity, and the established curve was compared with the H-Q curve based on the runoff observation. Two major findings were obtained: (1) a satisfied H-Q curve in which the error was 5-17% compared with measurement H-Q curve could be set up by using the data of one main flood event when there was a rain-gauge stations for each 30km2 in the basin or more; (2) a useful H-Q curve was still obtained by using a lot of flood events when the rain-gauge stations were sparse and were unevenly distributed.
