Robert, I've built a number of canoe jetties in my time on the Derg, Owenkillew, Strule/Mourne and the Camowen. The canoe ppl prefer a number of steps, ie a number of different levels, to accomodate holding the canoe in position at various different water levels in order to get aboard! Don't know what your range of water levels are but that would be the first thing to establish. Have you any experienced canoeists locally? Also, canoe jetties tend to be in pairs, a start and a finish if you like, maybe a mile apart. Possibly more important in white water stuff were it's not possible to paddle back to the start! good luck with your project, Alun