Estimation method of gorge section at a small river mouth

Field measurements have been carried out at the mouth of the Nanakita River, the catchment area being 229 km², with the object of finding difference of topography change between small and large rivers. Time-variation of the water level inside the river showed remarkable reduction of the amplitude and significant phase shift behind the tidal variation. On assuming a triangular or parabolic section, the width and the maximum depth at the gorge section are determined to minimize the difference between computed and measured water level inside the river mouth.