Flood

Flooding is an overflowing of water onto land that is normally dry (NOAA). There are various categories of floods. Coastal flooding is most frequently the result of storm surges and high winds coinciding with high tides (WMO, 2011).

A flash flood is a flood of short duration with a relatively high peak discharge in which the time interval between the observable causative event and the flood is less than four to six hours (WMO, 2006). A fluvial flood is a rise, unusually brief, in the water level of a stream or water body to a peak from which the water level recedes at a slower rate (WMO, 2012). A ‘glacial lake outburst flood’ is a phrase used to describe a sudden release of a significant amount of water retained in a glacial lake, irrespective of the cause (Emmer, 2017).

Floods affect more people than any other hazard. Worldwide, nearly 200 million live in coastal zones at risk of flooding. Flooding is usually the result of heavy or continuous rain that exceeds the absorptive capacity of the soil and the flow capacity of rivers, streams and coastal areas. Floods can be triggered by thunderstorms, tornadoes, tropical cyclones, monsoons, melting snow and dam breaks. The most common floods are flash floods, snowmelt floods, coastal floods and river floods. Flash floods and sudden floods are the most dangerous, especially when they occur at night.

Integrated Flood Management (IFM) is a process that promotes an integrated, rather than fragmented, approach to flood management. It integrates land and water resources development in a river basin, within the context of Integrated Resources Management, with a view to maximising the efficient use of floodplains and to minimising loss of life and property. IFM, like Integrated Water Resources Management, should encourage the participation of users, planners and policymakers at all levels (APFM).

Risk factors

  • Rapid population growth.
  • Rapid urbanization.
  • Environmental degradation: loss of forests and natural flood buffers.
  • Climate change will expose more people to future floods.
  • Melting glaciers and rising sea levels will bring floods to places not previously at risk.

Vulnerable areas

  • Developing countries are most at risk.
  • Although Asia remains the continent most hit by floods, Africa and Latin America are also heavily affected.
  • The poor, with the least means to adapt are often forced to live in high-risk places: slopes, flood plains, ravines, or in crowded, urban low-lying areas in mega-cities.

Risk reduction measures

  • Integrate flood risk assessment into urban planning strategies.
  • Avoid building on flood-prone land.
  • Develop new building codes to reinforce flood resistance.
  • Create more space for rivers, floodplains and wetlands.
  • Ensure health of coastal reefs and mangrove plantations.
  • Maintain early warning systems, backed up by regular drills and evacuation exercises.
  • Have an evacuation plan for those at risk, including the elderly, disabled and very young.
  • Catalyse finance and insurance schemes to protect assets and livelihoods.
  • Protect and evacuate animals.

Latest Flood additions in the Knowledge Base

Women walking on Malo Island, Vanuatu
The main cause of the flooding is the improper disposal of rubbish. People do not throw their rubbish in the right place and it’s their carelessness that is blocking the drainage and causing the flooding
International Federation of Red Cross and Red Crescent Societies (IFRC)
Cover
In this study, taking Yingtan city as an example, a system of indicators for evaluating Urban Flood Resilience (UFR) was constructed, with 17 representative indicators
Some sites have been used by humans for thousands of years.
Yale Climate Connections
Cover and source: Climate Services (Elsevier)
This study aims to assess farmers' adaptive capacity in two flood-prone districts of South Punjab. Results find that concern for climate change and knowledge of market value of crops were significant determinants for farmers adopting joint strategies.
Indian woman holding a water recipient on her head in the desert
Winter storms that provide crucial snow and rainfall to northern India are arriving significantly later in the year compared to 70 years ago exacerbating the risk of catastrophic flooding while also reducing vital water supplies for millions of Indians.
University of Reading
Cover
This article draws on a natural experiment to examine the causal link between flooding experiences, pro-environmental attitudes and pro-environmental behavior using national survey data collected from 2058 individuals aged 16-29 years across Luxembourg.
Flooding, Bentiu, South Sudan
In a new research paper, researchers set out to investigate what effect more frequent extreme Indian Ocean Dipole events would have on rainfall in east Africa.
Conversation Media Group, the
Pink water tube on the shore in Frederikssund in Denmark to prevent flooding from Storm Malik.
The weather of the future will be significantly wetter. Artificial intelligence can be used to develop early warning systems that can buy time to mitigate flood damage and to plan good systems to divert water away.
Technical University of Denmark

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