Lock gate cascade Another view from inside a lock. 2002-03-29T10:51 image image/jpeg 020329-1051-033 Kennet and Avon canal Nikon CoolPix 995 Zoom Nikkor 8-32mm 1:2.6-5.1 daylight To save construction costs, many of the Kennet and Avon canal locks were built without side-overflow channels. Instead, excess water is allowed to weir-flow over the lock gates. This is sometimes a pain for boaters and wasteful of water as it means that these locks must always be left empty, regardless of one's direction of travel.