|Posted by Pavan Vemula on January 29, 2010 at 5:37 AM|
1. Classification Based on Purpose
1. High Water Training: River training aimed at flood protection is called high water training or training for discharge. It envisages provision of adequate waterway for safe passage of maximum flood by proper location, alignment and height of embankments for a given flood discharge without tending to change river bed conditions.
2. Low Water Training: Also termed as training for depth. It envisages to provide adequate water depths during low water periods in the river channel for navigation by concentrating flow in
a desired channel and closing other channels by the method of bandalling, i.e., contracting the width of the river channel with the help of groynes, etc.
3. Mean Water Training: Also termed as training for sediment. It is by far the most important type of river training. It envisages rectification of the river bed configuration and efficient movement of suspended and bed load for maintaining the channel in good condition. The maximum aggrading capacity of a stream occurs in the vicinity of mean water or dominant flood discharge, and as such tends to change the river bed in accordance with that stage of bed flow. Mean water training includes river training for efficient sand exclusion from canals by correcting adverse river curvature to locate the canal offtake.
2. Classification Based on Structure Alignment
1. Longitudinal structure: These aim at guiding the axis of flow at ordinary and low stages, protecting the banks from erosion, generally to improve their alignment, trapping bed load in the areas of superfluous width, and establishing channel boundaries where braiding has created too wide a section divided into small channels separated by islands. Longitudinal training works are preferred to projecting training works in rivers carrying small bed loads, and with narrow channels having steep slopes and swift currents. In rivers with unstable bed cQnditions, longitudinal works are susceptible to damage by undermining.
2. Projecting training works. Projecting training works aim to protect the bank from which they project into the river by deflecting the current away from the bank. They are more suitable in rivers with unstable bed conditions. Cross connecting dikes to the bank at intervals add strength to withstand flood action and promote sedimentation in the closed-off channel spaces.