TRAINING OF RIVERS
Training of Rivers River training, in its wider aspects, covers all those engineering works which are constructed on a river, so as to guide and confine the flow to the river channel, and to control and regulate the river bed configuration , thus ensuring safe and effective disposal of floods and sediment loads. Stabilising and training the river along a certain alignment with a suitable waterway is, therefore, the first and formost aim of river training.
Objectives of River Training The river training works may serve the following objectives or advantages:
(i) To prevent the river from changing its course and to avoid outflanking of structures like bridges, weirs, aqueducts etc.
(ii) To prevent flooding of the surrounding countries by providing a safe passage for the flood waters without overtopping the banks.
(iii) To protect the river banks by deflecting the river away from the attacked banks.
(iv) To ensure effective disposal of sediment load.
(v) To provide minimum water depth required for navigation
Classification of River Training:
Depending upon the purpose for which a river training programme is undertaken, the river training works may be classified into the following three categories:
(1) High water training or Training for discharge
(2) Low water training or Training for depth
(3) Mean water training or Training for sediment
(1) High water training or Training for discharge:- High training is undertaken with the primary purpose of flood control. It, therefore, aims at providing sufficient river cross-section for the safe passage of maximum flood, and is concerned with making the adjoining area floodproof, by construction of dykes or levees, etc.
(2) Low water training or Training for depth:-Low water training is undertaken with the primary purpose of providing sufficient water depth in navigable channels during low water periods. it may be accomplished by concentrating and enhancing the flow in the desired channel by closing other channel by the process of bandalling by contracting the width of the channel with the help of 'groynes', etc.
(3) Mean water training or Training for Sediment:- Mean water training aims at efficient disposal of suspended load and bed load, and thus, to preserve the channel in good shape. The maximum acceretion capacity of a river occurs in river bed are attempted in accordance with that stage of flood flow. The mean water training is the most important type and forms the basis on which the former two are planned.
The following are the generally adopted methods for training rivers, including bank protection.
1. Marginal embankments or Levees.
2. Guide banks.
3. Groynes or Spurs.
4. Artificial cut-offs.
5. Pitching of banks and provision of launching aprons.
6. Pitched islands.