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.
In
meandering reaches, the study reaches are so demarcated as to identify
the
curved and straight portions. 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)
