12.5.8. Other River Training Methods In addition to the major river training methods discussed above, there are other types of training methods too. A reservoir can be constructed for controlling floods by storing water during a flood and releasing it after the flood has receded. Another effective and economical way of flood control is by diverting part of the flood discharge from the main river. The diverted water can flow through either a natural or an artificial river channel and ultimately either join a lake or meet the sea. Channel improvements (such as by reducing channel roughness, by dredging a channel to widen and deepen it, and by increasing discharge-carrying capacity of the river channel) enable it to pass the flood discharge at a relatively smaller stage. Soil conservation practices increase the infiltration and, hence, decrease the peak runoff.
Sills or ‘bed sills’ are useful in counteracting the tendency of excessive scouring (and, hence, deepening) in parts of the river cross-section. Bed sills are placed across the deepest part of the cross-section so as to partially block the flow in the deeper part of the channel. The flow near the bed is, therefore, diverted towards the shallower part of the channel. This increases the depth of flow in the shallower part. Sills are thus very useful to make non-navigable river bends navigable.
Artificial cutoffs (discussed in Sec. 12.3.3) are also useful training measures to divert the river from a curved path which might be endangering important land area.
EXERCISES
Describe different types of rivers.
What are the objectives of river training ?
Describe the following river training methods:
(i) Spurs, (ii) Guide banks, and (iii) Bank protection.
