How does flooding happen: causes, effects and solutions

It was past my bedtime when my parents woke my brother and me to ask for help. Our basement was flooding. How did this flooding happen? There had been severe, heavy rainfall that summer night and the water levels kept rising with no end in sight.

With scoops and buckets, we tried to bail as much water as possible. Until we smelled it. That horrid stench. My parents realized this wasn’t just rainwater, it was sewage. This was no place for six-year-old me—or any of us—to be.

Everything in that basement was ruined, including many toys and books in our playroom. Luckily, the rain subsided and we had insurance to help deal with the wreckage. But for many people who experience flooding globally, the effects of a flood are far worse, especially in low-income countries.

Flooding and poverty: the stats

Flooding has severe impacts on people's livelihoods in low-income and middle-income countries. They often have limited savings and little access to support systems. Low-income households face the most damaging and long-lasting effects after a flood.

• A group of researchers found that more than 780 million people on less than $5.50 per day live in places prone to flooding. That means four in ten people who are in susceptible areas have low incomes.
• About 1.81 billion people (23% of the world) are at risk of experiencing floodwaters deeper than 0.15 meters. This puts both lives and livelihoods in danger.
• Nearly nine out of ten at-risk people live in low‑ or middle‑income nations.
• East Asia and South Asia face some of the highest flood risks in the world. There are around 1.36 billion people living in crowded, vulnerable areas such as coastal zones and low‑lying river basins.

What is a flood?

A flood happens when water builds up faster than it can drain away, causing land that’s normally dry to be covered by water. It could be a few inches or several feet of water that engulf entire buildings. In any case, the effects of a flood leave costly damage to communities. They also pose severe medical and climate concerns.

What are the seven causes of flooding?

The cause of a flood can be a result of multiple contributing factors. Here are seven causes of flooding:

1. Heavy or prolonged rainfall

When rain falls too quickly or for too long, the ground can't absorb it. Rivers, lakes or drainage systems end up overflowing and damage surrounding areas.

2. Overflowing rivers

Rivers rise after heavy rain or snow melting upstream. If they exceed their capacity, water spills onto surrounding land.

3. Coastal flooding

Strong storms, hurricanes or cyclones can push seawater inland, also called a storm surge. High tides make this worse.

4. Melting snow or glaciers

Rapid melting of snow or ice—especially in spring—adds large amounts of water to rivers and streams. In 2025, Nepal—known as the "roof of the world" due to being home to the Himalayas— suffered from devastating floods which displaced thousands.

5. Dam or levee failure

If dams, levees of flood barriers break or are overwhelmed, water can overflow and rush into nearby areas.

6. Poor drainage and urbanization

Cities with a lot of concrete and asphalt have a reduced ability for water to be reabsorbed into the ground. Poor infrastructure or clogged drains can quickly lead to flash floods.

7. Climate and weather patterns

Climate change increases the frequency of intense rainfall and rising sea levels, making floods more common and severe. In fact, for each extra degree Celsius of warming enables the air to hold about seven per cent more water vapour.

Effects of a flood

Flooding can be dangerous, but with quick action and awareness, many risks can be reduced. Flooding has immediate impact but can also produce long-term challenges. Children are among the most vulnerable to physical harm and emotional trauma when a flood happens.

Human safety and health

When flooding happens, there are immediate dangers like deep water, loose debris or electrical hazards. Floodwater can also carry disease, bacteria or chemicals, which can lead to illness. At its worst, floods can result in loss of life. As little as six inches of moving water can knock a person down, and two feet of moving water can sweep a vehicle away.

Infrastructure damage

Floods can make roads, bridges, airports, homes and buildings inaccessible. The effects of a flood can also damage important systems like power and wastewater treatment.

Economic and social impact

Heavy flooding can disrupt a family’s livelihood and daily life. Businesses, farming fields and other income sources could take years to rebuild.

Environmental effects

The effects of a flood also prevent surrounding ecosystems from thriving. Flooding can harm the environment by washing away good soil, harming wildlife or polluting water sources.

Mental health

The effects of a flood go beyond just physical. In a flood, people experience deep loss, worry and grief.

Ways to prevent flooding

Flooding can’t always be completely stopped, but its risk and impact can be greatly reduced. Often rebuilding after a flood leads to safer, more resilient infrastructure for the future. Here are the main ways flooding is prevented or controlled, from small-scale actions to large, engineered solutions:

Natural and environmental solutions

• Wetlands and floodplains act like natural sponges, absorbing excess water and slowing river flow
• Planting trees and vegetation help the soil absorb water and reduce runoff and erosion
• Restoring rivers to follow natural paths and overflow safely reduces pressure downstream

Engineering and infrastructure solutions

• Dams and reservoirs store excess water during heavy rain and release it gradually
• Levees, embankments and flood walls prevent rivers or seas from overflowing into populated areas
• Improved drainage systems such as larger storm drains, culverts and regular maintenance prevent water buildup
• Permeable surfaces allow rain soak into the ground instead of running off

Urban planning and policy

• Smart land-use planning helps to avoid building homes in flood-prone areas like floodplains
• Flood-resistant buildings elevating houses, sealing basements and using flood-proof materials
• Zoning laws and building codes ensure new developments can handle heavy rainfall

What to do during a flood

• Keep nearby drains clear by removing garbage and debris, which helps water flow freely
• Collect rainwater to reduce runoff during storms
• Keep an eye on the weather and monitor alerts so you can prepare and evacuate early

How does World Vision Canada help communities prone to flooding?

World Vision Canada helps communities prone to flooding in several practical and life-saving ways—especially in countries where floods often cause major hardship. Our work combines emergency response with long-term resilience building so people are safer before, during and after flooding happens.

1. Emergency flood response

When floods hit, we’re often the first ones to arrive and the last ones to leave. We provide urgent supplies and services to help people survive and recover including:

• Essential relief items like tents or tarps for temporary shelter, blankets, kitchen sets and hygiene kits.
• Clean water and sanitation supplies like water purification tablets and safe storage containers reduce the spread of water-borne diseases.
• Health and protection support including basic health care supplies. We also ensure safe spaces for women and children to protect their well-being during crises.

2. Water, sanitation and hygiene (WASH) programs

Floods often destroy wells, contaminate water supplies and create conditions for disease to spread. That’s why we focus on ensuring access to clean water and sanitation before and after disasters.

• We provide immediate WASH services during emergency response to prevent outbreaks of cholera, typhoid and other flood-related diseases.
• We repair or rebuild wells and sanitation infrastructure so communities can safely use water again.
• We promote hygiene education to help families and schools practice safe habits that reduce illness risk during a flood and in the future.

3. Building local resilience to future floods

Beyond emergency aid, we work with communities to reduce their long-term vulnerability:

• Our community planning and early warning systems help people prepare for floods before they happen.
• Our livelihood programs help families recover faster and aren’t pushed into deeper poverty when floods damage crops.
• Training and partnerships with local organizations and authorities to strengthen disaster management.

Where do floods occur in the world?

Floods occur in areas that are susceptible to heavy seasonal rainfall, are situated in low elevation areas or are located near rivers or coasts. Here are the main at-risk regions:

South Asia and Southeast Asia have the highest global risk of flooding

These regions have large river systems and also experience intense monsoons and cyclones. Here, floods affect food security, health and housing, which is why we focus on providing disaster relief in this region.

• Bangladesh – Annual flooding affects millions in low-lying delta of the Ganges–Brahmaputra–Meghna rivers
• India – Assam, Bihar, Uttar Pradesh, Kerala and coastal regions
• Pakistan – Indus River basin and monsoon-affected areas
• Vietnam – Mekong Delta and coastal zones
• Philippines and Indonesia – Typhoons and flash floods

African countries south of the Saharan desert

Flooding is happening more often due to climate change and limited drainage infrastructure. High-risk areas include:

• Nigeria – Niger and Benue river basins
• South Sudan – Long-lasting seasonal floods
• Mozambique and Malawi – Cyclones and river flooding
• Democratic Republic of Congo – Heavy rainfall and river overflow

Coastal and river regions worldwide

Flood risk increases near oceans and major rivers:

• China – Yangtze and Yellow River basins
• United States – Mississippi River Basin, Gulf Coast, Florida
• Europe – Netherlands, parts of Germany, Italy and the UK
• South America – Amazon Basin (Brazil), Paraguay–Paraná river system

Rapidly growing cities susceptible to urban flooding

Cities with fast population growth and poor drainage are especially vulnerable:

• Jakarta (Indonesia) – Sinking city and heavy rain
• Mumbai (India) – Monsoons and dense urbanization
• Lagos (Nigeria)
• Manila (Philippines)

World Vision Canada's response to recent flooding events

World Vision Canada has connections to teams across the globe, enabling us to fund emergency responses in several countries in need. This allows us to respond quickly and efficiently to crises and natural disasters, supporting children and their families when they’re most vulnerable.

Ethiopia Floods (El Niño crisis, 2023–2024)

In late 2023, unusually heavy rains linked to El Niño caused devastating flooding in southern and eastern Ethiopia. The Somali Region was particularly impacted, affecting around 1.5 million people and displacing hundreds of thousands. Through generous donations and support through the Canadian Humanitarian Coalition and the Government of Canada, we were able to respond in the following ways:

• Distributing essential medicines and medical supplies to several health facilities to treat people affected by the floods.
• Rehabilitating damaged water systems, restoring access to safe drinking water for more than 920 households.
• Raising awareness about disease prevention (such as cholera and malaria) to reduce the risk of outbreaks after flood conditions.

Pakistan flood relief (ongoing)

Canadians have been helping World Vision Canada actively support people affected by major flood events in Pakistan, where monsoon rains and river flooding have caused widespread destruction. After historic floods, we mobilized emergency efforts to help families cope with the immediate aftermath.

• Providing emergency shelter, kitchen supplies, hygiene kits and water purification tablets for flood-affected families.
• Supporting emergency health clinics, treating water-borne diseases and other illnesses tied to flooding.
• Establishing women- and child-friendly spaces where vulnerable groups could find safe areas for rest and psychosocial support after displacement.

Nepal floods (2025)

Torrential and unseasonal rains triggered severe floods and landslides across Nepal, killing 51 peoples and displacing thousands. Children were without shelter, clean water or access to school.

• We provided immediate relief by ensuring affected children and families had access to clean water, food and safe spaces.
• We deployed response teams to support communities experiencing heavy loss, trauma and repeated flooding.
• We helped strengthen long‑term resilience by helping families adopt flood‑resistant farming, restore damaged land and establish early‑warning communication systems.
• Advocated for climate-aware preparedness, highlighting how climate change is driving more extreme and unpredictable weather in the region.

How to help countries prone to flooding

World Vision Canada is committed to fighting for children’s safety when a flood disaster occurs. With Canadians’ generous donations, we respond quickly to areas affected by flooding with immediate relief and long-term, sustainable solutions.

One of the best ways to support is through our emergency response donation when a flood happens. You can also partner with us on a monthly basis to support ongoing work in countries where children are most vulnerable.

Sponsoring a child in at-risk regions is another way to support a child’s community, giving them access to clean water, nutritious food, education, safety and more.