Explain why the city of Dhaka (in Bangladesh) experiences extreme flooding?

In short (click here for detailed version)

Dhaka experiences extreme flooding due to its geographical location in the Ganges-Brahmaputra delta, which receives heavy monsoon rainfall, coupled with rapid urbanization and inadequate drainage infrastructure, exacerbating the floods. Climate change also increases the risk of extreme weather events and sea level rise, worsening the situation.

Explain why the city of Dhaka (in Bangladesh) experiences extreme flooding?
In detail, for those interested!

Geography and Topography of Dhaka

Dhaka is located in the delta plain of the Ganges, Brahmaputra, and Meghna, one of the lowest regions in the world. This geographic position makes it particularly vulnerable to flooding. The city's topography is quite flat, and it is only a few meters above sea level, which does not help it stay safe from rising waters. During the monsoon season, torrential rains pour over the region, and with the already flat terrain, the water has nowhere to go. Dhaka is also surrounded by rivers, such as the Buriganga, which can easily overflow when there is excessive rainfall. This combination of flat terrain, a location at the heart of a vast river network, and abundant rainfall predisposes Dhaka to extreme flooding situations.

Impact of Climate Change on Precipitation Patterns

Climate change has truly disrupted the precipitation patterns in Dhaka. With rising global temperatures, there is an increase in evaporation, leading to more water vapor in the atmosphere. And this vapor must come down, often in the form of more intense and frequent precipitation. For Dhaka, this means even stronger monsoons than before. It is observed that the rainy season is becoming not only more intense but also more unpredictable. Flooding is more frequent and severe. The city's infrastructure is not equipped to handle these sudden and massive torrential rains. In fact, the urban system quickly becomes submerged. It's a real puzzle, between the water falling from the sky and the water stagnating without drainage in the streets.

Inefficient management of urban infrastructure

Dhaka is facing extreme flooding largely due to ineffective management of its urban infrastructure. The rapidly expanding city struggles to adapt its infrastructure to accommodate the influx of population. The drainage systems, often outdated, are not designed to handle such intense and regular rainfall. It's as if the sewage network is stuck in the past, unable to handle the current volume of water. Additionally, many sewer and drainage systems are clogged or poorly maintained. Imagine a deluge that grows and finds nowhere to go. The urban areas also lack rigorous urban planning, leading to haphazard constructions that block the natural flow of rainwater. All of this combines to turn neighborhoods into actual pools after every heavy downpour.

Drainage and stormwater management issues

Dhaka is not just a big city; it's also a headache when it comes to managing stormwater. The drainage systems are often outdated or undersized. Imagine pipes from another era, unable to handle the onslaught of heavy rains. Moreover, these infrastructures are often clogged with solid waste. Indeed, when sewers turn into garbage dumps, water struggles to find its path. Additionally, the region's clay soil complicates matters: it absorbs water less effectively, leading to faster flooding. Often, the modernization or maintenance of the drainage systems gets delayed. It's not easy to keep water flowing properly when everything is overwhelmed. Dhaka also grapples with illegal constructions encroaching on waterways, reducing drainage options. Add to that a lack of coordination among authorities, and you have a perfect recipe for repeated flooding. In short, it's like trying to empty a pool with a leaky glass.

Effects of deforestation and loss of wetlands

Forests and wetlands play a crucial role in absorbing rainwater and reducing the risk of flooding. When it comes to Dhaka, the situation becomes alarming due to massive deforestation and the loss of these valuable natural areas. Without these natural protections, rainwater has nowhere to go, which increases the likelihood of floods. Tree roots help to hold the soil in place, preventing erosion. When trees disappear, the soil degrades, and water flows unobstructed. Wetlands, on the other hand, act like giant sponges, absorbing excess water. Draining them or transforming them for urban development is like removing a giant sink plug—the water has no barrier. Dhaka is paying a high price for these environmental decisions, and every millimeter of rain becomes a threat, as nature is no longer there to provide a buffer.

Demographic pressure and rapid urbanization

The city of Dhaka is experiencing massive demographic pressure with a population exceeding 22 million inhabitants. Dhaka is one of the most densely populated cities in the world. Rapid urbanization leads to quick construction without sufficient consideration of the ecological impact or proper urban planning. The infrastructure cannot keep up with the frantic pace of urban expansion. New neighborhoods often emerge without adequate drainage systems, worsening the situation during heavy rains. Land is transformed to accommodate buildings and roads, consequently reducing permeable surfaces where water can naturally infiltrate. Informal settlements, or slums, swell in vulnerable areas and lack basic services. These conditions increase the flood risk exposure for thousands of people. All this is part of a vicious cycle where overpopulation combined with inefficient urban planning undermines the efforts to adapt to climate change.

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Frequently Asked Questions (FAQ)

1

What are the main geographical factors that make Dhaka vulnerable to floods?

Dhaka is located in the Ganges-Brahmaputra delta, a very low and flat region, making it prone to river floods and storm surges during the monsoon season.

2

How does climate change affect the frequency of floods in Dhaka?

Climate change is causing an increase in extreme precipitation and rising sea levels, exacerbating the risk of flooding in Dhaka.

3

What are the main shortcomings in the management of urban infrastructure in Dhaka?

Infrastructure in Dhaka is often poorly planned and undersized to handle the city's rapid expansion, exacerbating drainage issues and increasing the risk of flooding.

4

Why is the drainage system in Dhaka insufficient?

The city suffers from drainage systems blocked by waste and sediment, as well as poorly maintained or inadequate canals to handle massive rainwater during the rainy season.

5

How do deforestation and the loss of wetlands contribute to flooding in Dhaka?

Deforestation and draining of wetlands reduce the soil's natural ability to absorb precipitation, which increases runoff and the risk of flooding.

6

What is the impact of population growth on flood risks in Dhaka?

Rapid urbanization and demographic pressure lead to haphazard construction, often in flood-prone areas, exacerbating the consequences of floods.

7

What measures could reduce the risk of future flooding in Dhaka?

Measures such as improving drainage infrastructure, reforestation, protecting wetlands, and better urban planning could significantly reduce the risk of flooding.

Natural Sciences : Meteorology

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