Note 33 — Chapter III · The Working of a Canal.

The difficulty of reducing the size of a channel which is too large is well known and has been discussed in River and Canal Engineering, Chapter VIII. It is there explained that a moderate reduction of width can be effected by “bushing,” but that for great reductions, groynes or training walls are necessary. When the bed of a distributary is too low it has been suggested that it could be raised by filling in earth in each alternate length of 500 feet, and leaving the rest to silt, but this would be expensive.