CLIMATE CHANGE: IS BENGAL DELTA GOING TO BE SUBMERGED? KHONDKER NEAZ RAHMAN Urban And Regional Planner

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 Delta Swatch 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: - 37 o 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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