SUNDARBANS CASE STUDY - A-level Geography

General Knowledge

-The Sundarbans in the SW Bangladesh and E India, on the delta of the Ganges, Brahruptura and Meghna rivers on the Bay of Bengali.

-It is part of the largest mangrove forest in the world, protected as a National Park.

-Land is flat and low-lying, inter-seated by thousands of channels.

-In its natural state, the coastal system is in a state of dynamic equilibrium. Fluvial sediment is deposited my rivers, allowing the growth of mangrove forests. It is also eroded by the sea, so the size of the sediment store remains the same.

Coastal Processes - Tidal Action

• Tidal action: primary natural process shaping the distinctive coastal landscape; a dense network of river channels flows across the clay and silt fluvial deposits. The location of the main channels remains relatively statics as the silts and clays are resistant to erosion. The channels flow N-S due to strong tidal currents, and the smaller channels drains the land with each ebb tide.

Coastal processes - deposition

• Non-cohesive sediments lie sand are washed out of the delta and deposited on banks or at river mouths, where strong SW winds blow them into large ranges of sand dunes. With the protection of the dunes, finer silts washed into the bay are deposited, where wave action then adds and further deposits sand to form new islands. Vegetation establishes itself, and if natural succession can proceed, mangrove forests can develop.

Coastal Landforms - Mangrove forests

-Mangrove forests: collect sediments and slow down water flow, helping to mitigate against erosion. They can survive in brackish water as they filter salt.

Coastal Landforms - Deltas

-Deltas: formed from the deposition of sediment carried by a river as the flow leaves its mouth and enters slow moving water. Occurs when the river enters an ocean, sea or estuary and loses power so cannot support the transport of sediment.

Coastal Landforms - Mudflats

-Mudflats: huge quantities of river sediment (clay) deposited along a river's edge. Takes sediment away from the faster tidal currents as tides rise, slowing the river's velocity.

Coastal Landforms - Salt Marshes

-Salt Marshes: form in mudflats as silt sediments accumulate. Halophytes include mangrove trees, which colonise and stabilise the mudflat beneath them.

Coastal Landforms - Sand Dunes

Sand Dunes: creates as constructive waves wash large quantities of sand ashore. The strong SW monsoon winds blow sand onto the dunes, causing finer silts to be deposited. Vegetation establishes itself and mangrove trees grow.

Opportunities - Home to…

-Home to 4m people. Provides a range of products, services and opportunities for development to increase the wealth of Bangladesh.

Opportunities - Economic

-Economic: flat, fertile land of deltas is idea for growing crops. Ecosystem of mangrove forests provides populations with fish and crabs. Mangrove provides timber for construction.

Opportunities - Services

-Services: Mangrove forests provides a natural defence against flooding, acting as a barrier against tides and absorbs excess water in monsoon season. Roots also bind soil together, preventing erosion. Makes it easier to live and grow crops.

Opportunities - development

-Development: opportunities for tourism. Since 2001 cargo ships have been allowed to use the waterways. A power plant has been proposed for the N of the national park.

Occupation and Risks

-Lack of fresh water for drinking and irrigation, as fresh water is diverted from the rivers for irrigation use further upstream.

-Growing population has increased the removal of mangroves for agricultural land, increasing the risk of flooding and coastal erosion.

-Flooding can lead to salinisation of soil.

-Low-lying land at risk of rising sea levels.

-Poor region, and only 1/5 of households have access to mains electricity. Makes communication difficult, so residents don't receive flood warnings.

-Access is difficult - few roads, and those that exist are of poor quality. Limits opportunities for development, and makes it hard for residents to access goods, healthcare and education.

Resilience

-Being able to cope with the challenges of the environment.

-Public Health Department is increasing access to clear water and sanitation, improving QOL.

-Better roads and bridges are being built to improve access. However, this is leading to deforestation.

-Subsidised solar panels are being provided, making it easier for flood warnings to reach communities.

-Increasing food security by providing food subsidies. However, there is a risk that some areas may be farmed too intensively.

-NGOs are offering training in sustainable methods of farming to prevent over-exploitation from poor practice.

-MOST STRATEGIES RELY ON FUNDING FROM NGOs (non-governmental organisations).

Adaptation

-Adjusting behaviour to fit the environment.

-The environment of the Sundarbans will change due to sea level rise, so people will need to adapt to reduce risks and increase benefits.

1) Salt-resistant varieties of rice are being grown, helping residents cope with flooding. However, relying on a smaller range of crops will reduce biodiversity and increase vulnerability to disease.

2) Projects are underway to increase tourism, providing jobs and income e.g.lodges have been built. However, if not managed sustainable, it can create environmental damage.

3) People can adapt to sea level rise e.g. building houses on stilts, but roads and infrastructure cannot be protected as easily.

4) Sustainable development e.g. non-intensive farming practices and promoting eco-tourism will help ensure the fragile environment remains relatively undamaged.

Mitigation

-Reducing the severity of hazards.

1) 3,500km of embankments were built to prevent flooding. However, the embankments are gradually being eroded, and around 800km are being vulnerable to breaches during storms.

2) Coastal management projects aim to protect existing mangrove forests and replant areas that have been removed, to protect against flooding and erosion. But it is difficult to prevent illegal forest clearance. It is unclear if mangrove forests will withstand sea level rise.

3) The government and NGOs have provided funding for cyclone shelters and early warning systems, however many people may not have transport available to evacuate quickly.

Sea Level Rise

-Sundarbans is experiencing an alarming rate of sea level change; 3-8mm rise each year.

-Experiencing sea level rise due to eustatic change, caused by an increase in the ocean's water volume.

-Associated greenhouse gas emissions caused by human activity, consequently resulting in thermal expansion.

-Processes of the increasing frequency of cyclones and tidal surges damage mangroves, resulting in erosion of the coastline.

-Tidal waves vary from being 1-2m above sea levels and with sea levels rising by 2-8mm per year, waves are getting further onto the island and high and low tide levels are being submerged.

-A rise of 28cm of the coastline reduces the land available from 4200km2 in 2000 to 158km2.

-The submergence of land mass has rendered up to 6,00 families homeless and 70,000 people are immediately threatened with the same. This is causing the flight of human capital to the mainland - 13% in the past decade.

Mangrove Forests

-The Sundarbans stabilise the coast from tidal surges, and has shown that it can absorb up to 40% of a cyclone's power.

-Loss of the mangrove forest will result in the loss of the protective biological shield against cyclones and tsunamis. This may put the surrounding coastal communities a high risk.

-A tsunami against the Sundarbans has the potential to destroy enough mangrove forest to leave populated areas at risk from future cyclones as there will be a decrease in natural protection as the natural buffer is less. There is currently a density of 30 trees per 0.01 hectare, reducing the force of a tsunami by 90%. However 4% of the mangrove forest has been lost from erosion, contributing to 20m of the land being destroyed in some areas per year.