A simple method to include vertical resolution in a one-dimensional river model is outlined. The equations on which the method is based are the width-averaged continuity, momentum and transport equations. Some details are given on how to formulate the bed friction in a river model with vertical resolution. The equations are transformed to be in sigma coordinates. The numerical techniques, which make maximum use of an already implemented numerical solution technique in an existing river model, are described. The method is used to implement vertical resolution in the existing river model, MIKE 11. The implementation is tested on the following cases: logarithmic velocity profile, wind driven velocity profile, rapid accelerated flow, lock exchange and finally wind-forced entrainment. All test cases showed good agreement.