Abstract
Analytical solutions with respect to variation of river water levels in the tidal reach are presented for such boundary condition that the tidal oscillations of long period are given at a river mouth. The solutions are the approximate ones of the third order which are derived by a perturbation method and have the satisfactorily high accuracy compared with the ones of the second order. Based on those solutions, the relationships are theoretically investigated between the highest water levels along river channel and the hydraulic parameters, namely, amplitude and period of tidal oscillation at river mouth, river-bed solpe and river discharge. Highest water levels are also compared with water levels of the steady nonuniform flow when the water level at river mouth is kept constant at the peak level of tidal oscillation, in order to examine how safe it is to adopt the water level of nonuniform flow as the design high water level.
