flood mitigation

Background

Bangladesh is mostly a low-lying, flat delta

75% of the country is less than 10 m above sea level

80% of the country sits on the low-lying floodplains of the delta

Physical Cause

Climate change

Glacier ice melt in the Himalayas

Great intensity during the monsoon - more flooding

Cyclones come from the Bay of Bengal on the south

The Bay of Bengal is slowly rising - salt water is going into the freshwater in the Sundarbans

Sea level rise

Human Cause

The Ganges flows the longest from the Himalayan mountains to India for about 2000 km before it comes to Bangladesh, much of the water is taken up steam in India by the a series of dams (eg farakka), Bangladesh does not have enough water in the dry season, too much water in monsoon period

Primary Effects

Lost home 300 families (Patna river)

Covers 61 hectares in the village (Patna River)

Force to move inland - Dhaka

Fewer fish in the river

Sea level rise beyond 2025 - lose 17-20% of its land mass - at least 25-30 million people to be displaced within the country

The monsoon rainfall is predicted to rise by 40% by 2030

EXAMPLE

In 1998, 75% of Bangladesh was flooded, making 30 million people homeless

Over 1,000 people died

700,000 hectares of crops were destroyed

Secondary Effect

Have to move to Dhaka to find jobs to buy land to construct a new house

Slums in Dhaka receiving more and more refugees

20 million people without proper infrastructure in Dhaka

Not being able to go to school - not having enough money as forced to move multiple times

Cheap labour

Refugees live in miserable living conditions

⅓ of people live in slums in dhaka - slum clearance

Drinking water saline water - high blood pressure and other diseases

Management

Afforestation

planted mangroves and other trees along embankments and exposed shorelines to reduce wave energy, stabilise soils and support embankment protection against storm surges and river erosion

Embankments

Since the 1960s, Bangladesh has built extensive flood control, drainage and irrigation (FCD/FCDI) projects, centred on earthen embankments (levees) along the major rivers, coastal polders, sluice gates, and drainage channels.

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These works raise river banks, reduce overbank flooding, and protect cities, roads and farmland, but can also create drainage congestion inside protected areas during intense rainfall, so projects add or improve flood relief channels and regulators.

Dams

Bangladesh itself has relatively few large multipurpose dams on the main rivers, but flood management depends partly on upstream barrages and reservoirs in India and Nepal that can regulate dry‑season flow and influence monsoon peaks.

The national Flood Forecasting and Warning Centre

Bangladesh's Flood Action Plan, 1988, aimed to protect the country from future flooding . It was funded by the World Bank and a number of HICs

Evaluation

embankments suffer from erosion, overtopping and breaches due to poor construction, weak maintenance and public cuts// around 20% of the national budget is spent on embankments yet they still fail repeatedly and do not “solve the problem permanently”

Embankments can block natural drainage, so heavy monsoon rain inside protected areas often causes waterlogging unless major drainage works are added.

Embankments → higher flood levels in unprotected areas, disrupted fisheries, changing crop patterns), so embankments are effective locally but can shift risk elsewhere

SUCCESS:

Flood forecasting and warning are regarded as one of the more successful components: improvements since the 1990s have extended lead times to 3–5 days (and up to 10 days probabilistic), and WMO reports that these warnings have “proven very effective” in reducing loss of life and enabling early action