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rectangular pier under clear-water condition and
This paper presents models for daily flow forecast, found that when the group of piles is placed at a
dependable flow estimation and available flow distance of twice the projected width of the pier,
assessment for the dry season period in the for which percentage of blockage of the pier width
Jamuna. Daily discharge data of the Ganges at is 60%, the scour volume can be reduced upto 61%
Hardinge Bridge, the Jamuna at Bahadurabad and while the maximum scour depth can be reduced
the Padma at Baruria for the periods 1934-2002, upto 50%.
1956-2001 and 1966-2001 respectively have been
used in the study. 323 HOSSAIN, M.A. (Institute of Water and
Flood Management, BUET, Dhaka) & ISLAM,
Forecasting model for post-monsoon recession M.N. (Dept. of Physics, BUET, Dhaka).
flow and gradually increasing component of pre- Application of a Technique of Estimating
monsoon rising flow at Bahadurabad has been Rainfall using GMS- 5 IR Data in the Greater
developed based on at-site discharge data. Average Sylhet Region of Bangladesh. IWFM Res. Bull.,
absolute deviations of forecasted discharges for
recession and rising components are less than 2004, 5, 26-35.
respectively 8.6 and 9.2% of observed discharges
in 50% of the years. The low spatial and temporal resolution of GMS-5
system WEFAX data is not capable enough to
A probabilistic model based on disaggregation detect the extreme events and makes the system
approach has been developed for the estimation of unsuitable for forecasting of rainfall for flash
decad-wise dependable dry season flow at floods.In most cases it showed good
Bahadurabad. The 80% dependable flow is correspondence to the mid peaks. The GMS-5 data
3
st
approximately 11128 m /s in the 1 decad of is suitable for long time analysis of meteorological
3
November, decreases to 3322 m /s in the 1st decad processes involved in the Sylhet region. The data
3
of March and increases to 15647 m /s in the 3 rd quality has been a major obstacle in this project
decad of May. After satisfying in-stream flow of both in case of GMS-5 IR data and surface rain
3
3000 m /s at Baruria, available water at gauge data. The spatial and temporal resolution of
Bahadurabad for 80% dependable flow is 3773 GMS-5 data is less than adequate for forecasting
st
3
m /s in the 1 decad of February and decreases to rainfall with higher accuracy. Moreover most of
3
nd
3590 m /s in the 2 decad of March. the grid cells were partially covered by the ground
rain gauge stations. The calibration could be better
with improved and longer length of data.
322 HAQUE, M.A.; RAHMAN, M.M.;
ISLAM, G.M.T. & HOSSAIN, M.A.
(Institute of Water and Flood Management, BUET, 324 HUSSAIN, M.A.; AHMED, S,M.U.;
Dhaka). Scour Mitigation at Bridge Piers using BALA, S.K. & HOSSAIN, M.A. (Institute of
Sacrificial Piles. IWFM Res. Bull., 2003, 4, 23-32. Water and Flood Management, BUET, Dhaka).
Rainfall-Runoff Analysis of Korangi Flashy River
To mitigate scour around bridge piers, sacrificial Basin in Sylhet Area. IWFM Res. Bull., 2004, 5,
piles are economic method where natural processes 60-69.
are involved. The arrangement should be such that
scoured materials from the sacrificial piles should Stanford Watershed Model, Tank and NAM
have enough volume to fill the scour hole created Models were used to simulate rainfall-runoff for a
upstream of the pier in such a way that sediments small flashy basin of the Korangi river in Sylhet
are trapped inside the scour hole. This concept area. It is difficult to simulate rainfall-runoff of a
differs from earlier study made with sacrificial flashy basin without precipitation data from Indian
piles that mainly deals to reduce the strength of part. From model runs, analysis and on the basis of
horseshoe vortex. To determine the effect of the results of F-test on flow simulation and peak
sacrificial piles for scour mitigation, alternative value simulation and on correlation coefficients,
arrangements of piles were tested in front of a Stanford Watershed Model appears to be superior
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