Experiments in a flume with a compound section are described, in which lateral shear stress profiles were measured for various flow depths and inclinations of the main channel bank. General forms of bed shear stress profiles on the flood plain are described and the dependence of the turbulent interaction between channel and flood plain flows on flow depth and on the inclination of the main channel bank is examined. A dimensionless parameter is proposed for representing the intensity of turbulent interaction and is used as the independent variable to develop a model for predicting the shear stress profile on the bed of a flood plain. Equations are presented for predicting the value of this independent variable.