What should be the length and width of river for morphology study?
There are no rigid stipulations for length & width of river reach to be studied for morphological studies; these are dependent on a number of factors including the purpose of the study & the nature of the river channel.
Length to be studied:
In morphological studies, the river reaches to be studied are identified after detailed appraisal of the problem. The identified river reaches are then sub-divided into a number of study reaches such that a precise profile of the energy line may be established for the study.
Rigid criteria for the length of a reach obviously can not be laid down, but as a general rule, length of about 10 km is considered adequate.
Braided reaches of the river are sub divided in such a way that all major and minor channels separated by shoals and bars are covered for study.
Divided flow (twin channels) and long straight reaches are included in separate study reaches.
Estuarine reaches needs to be treated separately especially when the flow is bi-directional.
Width of river reach to be studied:
In each study reach, cross-sections are laid out normal to the direction of flow at an interval of about 5 km distance being measured along the centre line of the main channel.
River cross-sections should be studied up to the highest recorded water level for different years at /in:
- Existing gauge discharge sites (pre-monsoon and post-monsoon)
- The reaches affected by bank erosion and/or erratic river behaviour
(Please note that this is the minimum requirement)