On the influence of the features of morphologic structure of the floodplain and riverbed on the hydraulics of streams in channels with floodplains

Carried out is the analysis of methods of computation of discharge capacity of channels with floodplains. It is revealed that the standard technique recommended by the regulatory documents is uneffective. One of the causes for large computation errors is taking no account of the effect of interaction of the channel and floodplain flows. An empirical technique is recommended for the calculation, based on field observation data and graphical depth-velocity relations in relative coordinates. The technique based on the equation of stream motion with lengthwise-variable water discharge. Unfortunately, it requires additional studies on establishing dependences of the inertial terms of this equation on determining parameters.