In hydrological practice, flood routing is rarely achieved using the complete Saint-Venant equations. Instead, hydrological methods have been developed to provide users with simple methods that are robust yet efficient. The lag-and-route method has been widely used but its parameters have never been related to the physical parameters of channels. Moreover, the linear reservoir in this method is not well suited to reproduce effectively actual channel routing. A quadratic reservoir coupled with a lag component results in a far more accurate method while remaining numerically workable. This latter method depends on only two parameters which have been successfully related to physical channel features. This simple and efficient method enables one to gain insight into the main features of flood propagation in river channels.