Abstract:
The present study is mainly devoted to the evolvement of a
methodology to design a silt excluder, considering not only the
hydraulic parameters but also the sediment discharge including
bed and suspended load. The study also includes the estimation
procedure of the sediment entrainment through the canal head
regulator into the main canal.
In developing the design procedure of sediment excluder, a
mbdification over Garde and Pande Method (1976) was carried out.
The study also contains the best size, shape and location of
different component structures of a barrage situated in alluvial
plains. A literature survey of the existing barrages particularly
in the Indo-Pak'subcontinent together with the available scale
models has been also reviewed.
Considering above, the design of the Teesta Barrage Silt
Excluder has been evaluated and modifications suggested. It has
been observed that the present sediment excluder containing
discharge of 88.75% of canal discharge will have difficulty in
efficient functioning due to nonavailability of hydraulic head
for various flow conditions.
Teesta River carries 31 million tons of bed material load
yearly for 75% dependable flow, of which 75% is from suspended
load and 28% is from bedload. Teesta River carries sediment
particle range 0.074 to o.15mm, 0.15 to 0.30mm, 0.30 to 0.60mm
and >0.60mrn of 42, 42, 14, 2 and 17, 46, 33 and 4 percent
respectively from ,suspended load and bed mat~rial. A procedure to
estimate bed and sdspended sediment load to be entrain~d into the
main canal through the Canal Head Regulator of, the Teestsa
B,ar'ragehas also been given. Quantitative values of bed and
suspended sediment load with their various grain-size ranges are
also estimated.
Suggested rectification measures are also advised to
incorporate in the Tecata Barrage during the construction phase
of the project. Particularly a corrective measure was suggested
for no entrainment of bed load and a reduction of 52% of the
suspended load entrainment per year for lO-day average 75%
dependable flow of the Teesta River based on the analysis of 33 .
years data.
The possibility of the installation of a sediment ejector in
the Teesta Main Canal was also studied arid found to be suitably
arranged provided some modifications in the crest level of CHR,
FSL and canal bed of main canal are considered.
