ABSTRACT

The proportional method only includes correction of the constant k with time. Thus, the temporal variation of the bottom friction level is assumed to be independent of the magnitude of discharge. Focus point interpolation uses the assumption that all QH-curves have a shared fictive point where all QHrelationships focus. The focus method assumes that the bottom friction ·level is reduced relatively for high discharge levels, i.e. the bottom frictio!l due to weed and sediment obstruction are reduced during increased discharge. Both k and n are corrected and interpolated in the focus point method.