The analytical solution to the Boussinesq equations for solitary waves trav
elling in uniform water channels with sloping side walls is presented. Quan
titative effects of channel cross-sectional geometry and channel side-wall
slope at the waterline on the wave profile and wave speed, as well as the c
riteria for positive solitary waves to exist, are discussed. The new Boussi
nesq solution is also compared with the existing Korteweg-de Vries solution
obtained by Peregrine. It is found that the two solutions are consistent f
or small amplitude waves while, for relatively large waves, the Boussinesq
solution gives different predictions for wave speed and for the criteria fo
r solitary waves to exist.