hydrologic characteristics of floods in ganges-brahmaputra- meghna (gbm) delta a.k.m. saiful islam...
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![Page 1: Hydrologic Characteristics of Floods in Ganges-Brahmaputra- Meghna (GBM) Delta A.K.M. Saiful Islam Sujit Kumar Bala Institute of Water and Flood Management](https://reader031.vdocuments.net/reader031/viewer/2022032005/56649d355503460f94a0cf11/html5/thumbnails/1.jpg)
Hydrologic Characteristics of Hydrologic Characteristics of Floods in Ganges-Brahmaputra-Floods in Ganges-Brahmaputra-
Meghna (GBM) DeltaMeghna (GBM) Delta
A.K.M. Saiful Islam
Sujit Kumar Bala
Institute of Water and Flood Management (IWFM)Bangladesh University of Engineer and Technology (BUET)
International Symposium “Hazard Management for Sustainable Development”29th November, 2009, Kathmandu, Nepal
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Outline of the Presentation
Main Causes of Floods in Bangladesh
Hydrologic Aspects of Past Major Floods
Flood Inundation Maps using MODIS images
Performance of Flood Control Works around Dhaka City.
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The Ganges, Brahmaputra, and Meghna (GBM) River Basins
• 93% water comes outside of Bangladesh
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River System and GBM Grid
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TRMM Rainfall over GBM
3 hourly rainfall with spatial resolution 0.25 degree
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Rainfall (May-Sep, 1998)
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Rainfall (May-Sep, 2004)
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Rainfall (May-Sep, 2007)
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Normalized Monthly Rainfall
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Monthly rainfall over GBM basin during July using TRMM 3-hourly data.
• Ganges
• Brahmaputra
• Meghna
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Chronology of the entrance of 2007 Flood
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Water Level Stations in Major Rivers
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Height of Peak above DL
2007 2004 1998 1988
Brahmaputra 0.88 0.68 0.87 1.12
Ganges - - 0.94 0.62
Meghna 0.69 1.53 1.08 1.41
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Duration of flood above DL
2007 2004 1998 1988
Brahmaputra 21 15 67 16
Ganges 0 0 26 23
Meghna 37 38 67 75
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Floods in Major Rivers1988 1998
2004 2007
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Brahmaputra at Bahdurabad
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18-S
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28-S
ep
Wat
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(m
,PW
D)
1988
1998
2004
2007
DL
RHWL
RHWL
DL
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Ganges at Hardinge Bridge
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(m
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1998
2004
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DL
RHWL
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DL
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Meghna at Bhairab Bazar
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Wat
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(m
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1998
2004
2007
DL
RHWL
RHWL
DL
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Flood Inundation Map based on MODIS Satellite Data
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Land Use Classifications
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MODIS derived Indices
REDNIR
REDNIRNDVI
15.765.2
BLUEREDNIR
REDNIREVI
SWIRNIR
SWIRNIRLSWI
Where, Band 1: Red , Band 2: NIR, Band 3: Blue, Band 6: SWIR
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Time Series of land use data
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Flow Chart of Inundation Map
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Flood Inundation Map for 2004 & 2007
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Start, End and Duration of Floods in 2004 & 2007
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Flood control Works around
Dhaka City
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Performance of Flood control works around Dhaka city during 2007
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Goran chatbari
Kallayanpur
Dholai Khal
Segun bagicha
Rampura
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Rampura temporary pump station shows negligible impact on drainage congestion
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Temporary pumps near Hazaribag discharge untreated waste water which cause serious
pollution of Buriganga river
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Retention ponds of Kallayanpur pump station Encroachments gradually increases and
reduces retention pond area. Authority should act immediately
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Dredging in Turag river filsl wetlands of Dhaka west. Serious thread to retention ponds of
Goran chatbari pumping stations.
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Floating mat of waste on Dholai khal indicates poor solid waste management of the Dhaka city
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Conclusions
• The main source of floods in Bangladesh is the rainfall in the upper catchment of the Ganges, the Brahmaputra and, the Meghna river basins.
• The mean monthly rainfall plot of TRMM satellite data shows that the rainfall is higher for both the Meghna and the Brahmaputra basins, during July 2007 than during the last two years.
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• In terms of magnitude and duration, the flood of 2007 was more severe in the Brahmaputra basin than the flood of 2004.
• The magnitude of the Meghna in the flood of 2007 was well below the magnitude of the flood of 2004.
• However, the Meghna was in the flood stage above the danger level for a duration that was similar to the river floods in 2004.