We address the issue of the exponential stability (in L2-norm) of the classical solutions of the linearised Saint-Venant equations for a sloping
channel. We give an explicit sufficient dissipative condition which guarantees the exponential stability under subcritical flow conditions without additional assumptions on the size of the bottom and friction slopes. The stability analysis relies on the same strict Lyapunov function as in our previous paper (IEEE, 2007). The special case of a single pool is first treated. Then, the analysis is extended to the case of the boundary feedback control of a general channel with a cascade of n pools.