Abstract
The basic principle of the unit hydrograph method assumes that there exists a linear relation between the discharge Q(t) and the rainfall r(t) expressed as
Q(t)=∫t-∞ X(τ)r(t-τ)dτ,
where X(t) is the unit hydrograph given as a kernel of the linear integral equation.
Since this expression is obviously based on emperical relations, the hydraulic significance of the unit hydrograph method will be lost, unless a dynamical basis of the above expression is verified in the light of fluid mechanics.
Under these considerations, the present paper deals theoretically with the following two themes from a stand point of hydraulics.
1) Hydraulic significance of the fundamental principle of the unit hydrograph method.
2) The most preferable elements of the unit rainfall and the unit hydrograph, and estimation of errors due to the application of the unit hydrograph method.
The authors hope that the results derived in the present paper will bring effective procedures to solve important practical problems such as the range of applicability of the unit hydrograph method or the synthetic unit hydrograph and so on.
