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What are the Different Types of Floods?

Melissa Barrett
Melissa Barrett

For ease of classification, different types of floods are often identified by their cause. Floods occur for many reasons, from the torrential but predictable rains of monsoon season to the sudden massive water wall of a tsunami. Unfortunately, almost any body of water has the potential to flood. Heavy rains can overfill rivers and streams, leading to flash flooding. Coastal communities can find themselves swamped by ocean waters from hurricanes.

Flash flooding is sudden, severe, and often potentially life threatening. When sudden rains or spring snowfalls occur in higher elevations, the water runs down, gathering speed as it travels. Often, smaller flows of water combine with larger flows repeatedly until they converge on a river or streambed. By then, the massive amount of water is flowing so quickly that it can destroy almost anything in its path. Trees, cars, and sometimes homes can be swept away by the rushing water.

Destruction in the Ninth Ward of New Orleans. Storm surge flooding from Hurricane Katrina destroyed many homes in this area of the city.
Destruction in the Ninth Ward of New Orleans. Storm surge flooding from Hurricane Katrina destroyed many homes in this area of the city.

Like flash floods, monsoon floods are often caused by large amounts of rain falling in a short period of time. Flash floods, however, are generally localized. Monsoon rains tend to affect larger areas, causing more damage and higher loss of life. Monsoon rainfall is generally repeated several times within a season. Each rainfall poses more potential for flooding as large amounts of rain are dumped on ground that is saturated and rivers that are already overflowing their banks.

Hydroelectric power generating stations like the Hoover Dam also provide flood control for the river basins they occupy.
Hydroelectric power generating stations like the Hoover Dam also provide flood control for the river basins they occupy.

Those in warm-weather coastal areas can find themselves at the mercy of flooding caused by hurricanes. Along with the drenching rains that are typical with hurricanes, residents often have to deal with seawater driven into their communities by gale-force winds. Compounding the risk, many ocean-side settlements are built on land that is near to or in part below sea level. These communities often rely heavily on levees to keep ocean waters at bay.

Flash flooding can create dangerous road conditions.
Flash flooding can create dangerous road conditions.

Unlike most types of floods, tsunamis are largely unaffected by weather patterns. These gigantic waves are instead caused by earthquakes or volcanic eruptions in or near large bodies of water. Tsunamis are among the most catastrophic types of floods both in property damage and loss of life.

One of the deadliest tsunamis on record is the 2004 Indian Ocean Tsunami. This tsunami was started by an earthquake in the Indian Ocean and caused massive damage in several coastal countries including Indonesia, Sri Lanka, India, and Thailand. The death toll was estimated at over 220,000.

Monsoons usually occur several times in one season, leading people in affected countries to take precautions against regular flooding.
Monsoons usually occur several times in one season, leading people in affected countries to take precautions against regular flooding.

Sometimes, human construction and inclement weather combine to form deadly floods. Such a disaster occurred on 8 August 1975 in the Henan province of China. On that day, typhoon-force rains overwhelmed the Banquito Dam on the Ru River. The resulting wall of water and debris swept down the Ru at speeds in excess of 30 miles (approximately 50 kilometers) per hour. It was estimated that 26,000 people died in the flood, including the entire 9,600 population of the town of Daowencheng.

Frequently Asked Questions

What are the main types of floods?

Tsunamis are among the most catastrophic types of floods both in property damage and loss of life.
Tsunamis are among the most catastrophic types of floods both in property damage and loss of life.

There are several main types of floods, including riverine floods, which occur when rivers overflow their banks; coastal floods, caused by storm surges and high tides; pluvial floods, resulting from heavy rainfall that doesn't drain away; flash floods, which are rapid and extreme flow of high water into a normally dry area; and catastrophic floods, often due to dam failures or ice jams.

How do flash floods differ from other types of flooding?

Tsunamis are massive ocean waves caused by earthquakes or volcanic eruptions.
Tsunamis are massive ocean waves caused by earthquakes or volcanic eruptions.

Flash floods are characterized by their sudden onset and rapid development, often within minutes or hours following heavy rainfall, a dam break, or a sudden release of water held by an ice or debris jam. They can roll boulders, tear out trees, and destroy buildings and bridges, making them particularly dangerous and unpredictable compared to slower rising floods.

What causes coastal flooding?

Streams can overflow, leading to flash flooding.
Streams can overflow, leading to flash flooding.

Coastal flooding is primarily caused by storm surges associated with tropical cyclones, hurricanes, or typhoons, as well as by tsunamis. These events push seawater onto land, which can be exacerbated by high tides and sea-level rise. According to the National Oceanic and Atmospheric Administration, storm surges can raise water levels by 30 feet or more, leading to significant coastal flooding.

Can urban development increase the risk of flooding?

In some instances, flash floods caused by rainfall may begin to subside after the rain stops without posing too much danger to inhabitants of the area.
In some instances, flash floods caused by rainfall may begin to subside after the rain stops without posing too much danger to inhabitants of the area.

Yes, urban development can significantly increase flood risk. The construction of buildings, roads, and other infrastructure reduces the land's natural ability to absorb rainfall. According to the Environmental Protection Agency, impervious surfaces in urban areas can lead to 55% of rainfall becoming runoff, compared to just 10% in a natural environment, thereby increasing the likelihood and severity of pluvial floods.

What is a riverine flood and how does it occur?

A riverine flood occurs when water levels in a river or stream exceed the capacity of the river channel, often due to prolonged rainfall or snowmelt. This type of flooding can be exacerbated by factors such as ice jams, which block the flow of water, or human activities like deforestation and the alteration of waterways, which can change the natural flow of rivers.

Are there any long-term solutions to mitigate the impact of floods?

Long-term flood mitigation involves a combination of structural and non-structural measures. Structural solutions include the construction of levees, dams, and floodwalls, while non-structural strategies involve land-use planning, floodplain zoning, and the restoration of natural ecosystems. According to the United Nations Office for Disaster Risk Reduction, effective flood risk management requires integrating both approaches to reduce vulnerability and enhance resilience.

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    • Destruction in the Ninth Ward of New Orleans. Storm surge flooding from Hurricane Katrina destroyed many homes in this area of the city.
      By: Brian Nolan
      Destruction in the Ninth Ward of New Orleans. Storm surge flooding from Hurricane Katrina destroyed many homes in this area of the city.
    • Hydroelectric power generating stations like the Hoover Dam also provide flood control for the river basins they occupy.
      By: William Warby
      Hydroelectric power generating stations like the Hoover Dam also provide flood control for the river basins they occupy.
    • Flash flooding can create dangerous road conditions.
      By: Anthony Hall
      Flash flooding can create dangerous road conditions.
    • Monsoons usually occur several times in one season, leading people in affected countries to take precautions against regular flooding.
      By: Nomad_Soul
      Monsoons usually occur several times in one season, leading people in affected countries to take precautions against regular flooding.
    • Tsunamis are among the most catastrophic types of floods both in property damage and loss of life.
      By: satori
      Tsunamis are among the most catastrophic types of floods both in property damage and loss of life.
    • Tsunamis are massive ocean waves caused by earthquakes or volcanic eruptions.
      By: EpicStockMedia
      Tsunamis are massive ocean waves caused by earthquakes or volcanic eruptions.
    • Streams can overflow, leading to flash flooding.
      By: Galyna Andrushko
      Streams can overflow, leading to flash flooding.
    • In some instances, flash floods caused by rainfall may begin to subside after the rain stops without posing too much danger to inhabitants of the area.
      By: Ronald Hudson
      In some instances, flash floods caused by rainfall may begin to subside after the rain stops without posing too much danger to inhabitants of the area.