It is well-known that the method of unit hydrograph is developed on the basis of three postulates allowing summing of hydrographs. In the article the special case of such summing is considered when all components of total flooding are identical on form but are formed by some delay due to dynamics of change of meteorological situation. The suggested dynamic model of flooding of area caused by drainage from several nonequally loaded tributaries of watershed. The dynamic scenario of flooding is that all identical tributaries of watershed are loaded by precipitation in different level. The causes of that are such factors as non-equal water content of clouds, delayed incoming of clouds to some tributaries of watershed etc. It is shown that the considered model of flooding with set of unit delayed hydrographs theoretically can possess the maximum depending on watershed content and duration of effective rains.