The total length of the main spillway
including the two side spillways
is 13.80m. The length of each side
spillway is 1.20m. Timber logs are used
to control water flows of the two side
spillways. Three timber logs are used
for each side spillway. The length of
each timber log is 1.60m.
The main spillway is designed to pass a
maximum of:
- 6.35cu.m/sec, at maximum water level
of 103.60m, if the two side spillways are
closed.
- 5.25cu.m/sec, at maximum water level
of 103.60m, if the two side spillways are
opened.
- 3.73cu.m/sec, at maximum water level
of 103.60m.
Sluice Gates System: The three sluice
gates are introduced to pass extra
floodwater and clear silt upstream of
the structure. The diameter of each
sluice gate is 76cm. The length of
each steel pipe is 2.50m with 76cm
diameter. The three sluice gates are
designed with 76cm diameter to pass a
maximum discharge of 6.42cu.m/sec, at
a maximum water level of 103.60m.
Canal System: Branch Canals: There
are a number of small watercourses
upstream fed by Canal A and Canal
B, which divert part of the retarded
floodwater to irrigate agricultural land.
Canal A has a water discharge rate
ranging from 3.26 to 23.96cu.m/sec at a
maximum water level of 103.60m. Canal
B has a water discharge rate ranging
from 0.0cu.m/sec to 1.69cu.m/sec at a
maximum water level of 103.60m.
- Canal A:
bottom width = 8.3m and crest level =
102.24m
- Canal B:
bottom width = 2.0m and crest level =
103.00m
If Canal B is widened to a bottom width
of 4.0m, the diverted water discharge
will be doubled.
Protective Embankment: Shangil
Tobaya village needs to be protected
against the backwater effect of retarded
and stored floodwaters. The existing
embankment needed rehabilitation to
withstand the maximum water level of
103.60m. The typical cross-section of
the embankment can be taken to be:
- Bottom width
= 7.25m
- Top width
= 1.00m
- Upstream side slope =
1 vertical:
2.5 horizontal
- Downstream side slope =
1 vertical:
2.5 horizontal
Operation Procedures: Most of the
floodwater is diverted to irrigate
adjacent agricultural land. If the three
sluice gates are closed for some period,
silt is expected to be deposited upstream
of the earth dam. Therefore, these gates
should be opened frequently to flush the
deposited silt. The sluice gates can also
be opened to meet irrigation demands
downstream.
PRACTICAL ANSWERS
TO POVERTY
9