climate change: is bengal delta going to be submerged? khondker neaz rahman urban and regional...
TRANSCRIPT
CLIMATE CHANGE: IS BENGAL DELTA GOING TO BE SUBMERGED?
KHONDKER NEAZ RAHMAN
Urban And Regional Planner
E-mail: [email protected]
INTRODUCTION
Three major rivers:
a. Padma (Ganges)b. Jamuna
(Brahmaputra)c. Meghna
Stretches from
Hugli River to
Meghna River
INTRODUCTION (cont.)
Divided into
Western Inactive Delta & Eastern Active Delta
Size of the Delta is 105,645 Sq Km (40,790 sq. miles). Largest river delta.
Formation Started Approx. 125Ma
INTRODUCTION (cont.)
Subaqueous DeltaSwatch of No Ground
STATEMENT OF THE PROBLEM
SEA LEVEL RISE.
STATEMENT OF THE PROBLEM. (cont.)
2.4 billion metric ton (approx) annual alluvium carried through Ganga-Brahmaputra-Meghna river system.
Change in water cycle
Evaporation-Condensation-Precipitation
will increase with rise of temperature .
STATEMENT OF THE PROBLEM. (cont.)
Temp rise will uncover more soil on the Himalaya range.
Will result in-
1. Increase of vulnerability of erosion during precipitation.
STATEMENT OF THE PROBLEM. (cont.)
2. Higher snow fall & melting of glacier – GLOF (Glacier Lake Outburst Flood)
STATEMENT OF THE PROBLEM. (cont.)
3. PERMAFROST (FROZEN LAND) –
Increase vulnerability of erosion
STATEMENT OF THE PROBLEM. (cont.)
RESULT:
Change in sedimentation pattern
STATEMENT OF THE PROBLEM. (cont.)
CHANGE IN SEA CURRENT
STATEMENT OF THE PROBLEM. (cont.)
RISE IN TEMPERATURE ….
May result in rise of sea level Will change Sea Current Character Will increase precipitation Higher melting of Ice Cap and Permafrost
STATEMENT OF THE PROBLEM. (cont.)
…WILL RESULT IN
Increased soil erosion from Himalaya Decrease in silt carrying capacity of Meghna
river. Change in siltation Pattern near the
SUBAQUEOUS Delta.
STATEMENT OF THE PROBLEM. (cont.)
Nature and history of climate and geology reveals that rise and fall of temperature has created conditions for the development of Bengal Delta.
“Water does not tear down Delta; instead it builds up a Delta”.
STATEMENT OF THE PROBLEM. (cont.) Historical evidence. Time Frame: At the end of the last ice age, around
6000 years ago Event of Nature: Sea level rose somewhere between
6 to 10 m above MSL (mean sea level). Geographical Area: The coastline of Midnapur region
of Bengal delta. Observation: The distribution of early historic sites in
the region does not support the idea that the coastline changes were historically significant.
Lesson: When such a sea level rise took place the ancient coastline of Midnapur coast could moved only 10 to 15 km towards north.
“Archaeological geography of the Ganga Plain. The Lower and the Middle Ganga”, author is Dilip Kumar Chakrabarti from Cambridge University, published in 2001
ISSUES AND QUESTIONS TO BE PONDERED
ANTARCTICA-
90% of the world ice. Temperature: - 37o C Covered by ice of average 2 Km thickness
ISSUES AND QUESTIONS TO BE PONDERED
What will happen if temperature around ANTARTICA increases?
Greater precipitation.
Results in higher snow fall in Antarctica?
ISSUES AND QUESTIONS TO BE PONDERED
NORTH POLE
ARCTIC OCEAN-
Mostly ice- Floats on the Arctic Ocean.
ICEBERG
ISSUES AND QUESTIONS TO BE PONDERED
Globally ICE represent 2% of the world water.
ISSUES AND QUESTIONS TO BE PONDERED
In their SciencExpress article, Curt Davis (University of Missouri-Columbia) and his collaborators used satellite radar altimetry measurements from 1992 to 2003 to determine that, on average, the elevation of about 8.5 million square kilometers of the Antarctic interior has been increasing (Figure 1). The increasing elevation was then linked to increases in snowfall, which was translated into a mass gain of 45 ± 7 billion tons per year, tying up enough moisture to lower sea level by 0.12 ± 0.02 millimeters per year.
ISSUES AND QUESTIONS TO BE PONDERED
Figure 1. Rate of elevation change (cm/yr) from 1992 to 2003 as determined by satellite altimetry measurements (from Davis et al., 2005).
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