Abstract
This paper aims to propose the lumped model of two-dimensional inundation flow in macro scale. This model ensures numerical compatibility with a basin-widely distributed runoff one in modeling accuracy and simplification. An inundating domain is divided into many infinitesimal elements constitutied of one straight and short channelin micro scale. Based on the Navier Stokes equations, the mass conservation and motion equations of inundating flow in this channel are successfully simplified. The resulting motion equation is in conformity with the Fourier's and the Darcy's Laws. It is lumped in macro scale with the other elements. It can be shown that the basic equation of inundating flow in macro scale is finally categorized in the group conformable to water-depth transfer phenomenon.
