Flooding
type: Concept
definition: Flooding is (1) an overflowing by water of the normal confines of a watercourse or other body of water; (2) an accumulation of drainage water over areas which are not normally submerged; (3) a controlled spreading of water for irrigation (WMO and UNESCO, 2012).
alternative label: Flood
alternative label: Inundation
alternative label: High Water
note: Whereas floods are defined in hydrology as a "(1) rise, usually brief, in the water level of a stream or water body to a peak from which the water level recedes at a slower rate, (2) relatively high flow as measured by stage height or discharge" (WMO and UNESCO, 2012), flooding represents the hazard associated to with these peaks whenever the water overflows the normal confines of the water body. Flooding can include: - Coastal Flood: Coastal flooding occurs from multiple sources, including from storm surges, waves and swell, seiches, riverine and flash floods near the coast, tides, sea-level rise and tsunamis. It is most frequently the result of storm surges and high winds coinciding with high tides. The surge itself is the result of the raising of sea levels due to low atmospheric pressure. In particular conditions, such as major estuaries or confined sea areas, the piling up of water is amplified by a combination of the shallowing of the seabed and retarding of return flow (WMO, 2011; WMO, 2022). - Estuarine (Coastal) Flood: Estuarine flooding is flooding over and near coastal areas caused by storm surges and high winds coincident with high tides, thereby obstructing the seaward river flow. Estuarine flooding can also occur when riverine flooding causes overflow near the estuary or coastal zone, and in specific cases, can also be caused by tsunamis. (WMO, 2011). Therefore, it is challenging to identify a single driver for estuarine flooding. - Flash Flood: A flash flood is a flood of short duration with a relatively high peak discharge (WMO, 2021). - Fluvial (Riverine) Flooding: Overflowing by water of the normal confines of a watercourse or other body of water (WMO, 2012). - Groundwater Flood: A groundwater flood is the emergence of groundwater at the ground surface away from perennial river channels or the rising of groundwater into man-made ground, under conditions where the 'normal' ranges of groundwater level and groundwater flow are exceeded (BGS, 2010). - …
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: Floods tend to be caused by a number of natural events such as rain from slow- moving or stationary low-pressure areas, thunderstorms, and tropical cyclones. The amount and duration of the rainfall, soil type and saturation, geography and whether it is an urban area can affect the magnitude and impacts of the flooding. Flooding can occur at the place of a heavy rain event or far downstream away from the causal rain event. Flooding can also be caused by other factors such as storm surges, tsunamis, ice jams and glacial lake outbursts, as well as being human influenced through dam bursts, improper land use planning, etc. (Geoscience Australia, no date).
  type: drivers
source: 35589-international-glossary-of-hydrology
was quoted from: 35589-international-glossary-of-hydrology
references: descriptionSource1
references: groundwater flooding.html
references: https://oxfordre.com/naturalhazardscience/view/10.1093/acrefore/9780199389407.001.0001/acrefore-9780199389407-e-275
references: flood
references: https://onlinelibrary.wiley.com/doi/full/10.1111/jfr3.12855
references: FlashFloodingDefinition
references: https://www.nssl.noaa.gov/education/svrwx101/floods/
references: S2382624X21400038
references: 35589-international-glossary-of-hydrology
references: https://library.wmo.int/records/item/40434-integrated-flood-management
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references: https://library.wmo.int/viewer/48739
references: https://library.wmo.int/records/item/35631-technical-regulations-volume-iii-hydrology
references: 58169-guidelines-on-implementation-of-a-coastal-inundation-forecasting-early-warning-system
references: descriptionSource16
references: floods
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
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was influenced by: flood
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was influenced by: FlashFloodingDefinition
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was influenced by: floods
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caused by: Subsidence and Uplift
caused by: Thunderstorm
caused by: Depression or Cyclone (Low Pressure Area)
caused by: Extra-tropical Cyclone
caused by: Sub-Tropical Cyclone
caused by: Tropical Cyclone
caused by: Rain
caused by: Dam Failure
caused by: Reservoir Flooding
causes: Lahars
causes: Gravitational Mass Movement (‘Landslide’)
causes: Debris and earth (mud)flows and rock avalanches
causes: Rock, debris and earth (mud) slide
causes: Soil Degradation
causes: Soil Erosion
causes: River Erosion and Accretion
causes: Coastal Erosion and Accretion
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
causes: Cholera
causes: Locust upsurge
causes: Fungal Plant Disease
causes: Human-Wildlife Conflict
causes: Snakebite envenoming
causes: Explosive Ordnance
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure

Flooding
type: Concept
type: chapeau

Meteorological and Hydrological
type: Concept
type: type

Water-related
type: Concept
type: cluster

Subsidence and Uplift
type: Concept

Thunderstorm
type: Concept

Depression or Cyclone (Low Pressure Area)
type: Concept

Extra-tropical Cyclone
type: Concept

Sub-Tropical Cyclone
type: Concept

Tropical Cyclone
type: Concept

Rain
type: Concept

Dam Failure
type: Concept

Reservoir Flooding
type: Concept

Lahars
type: Concept

Gravitational Mass Movement (‘Landslide’)
type: Concept

Debris and earth (mud)flows and rock avalanches
type: Concept

Rock, debris and earth (mud) slide
type: Concept

Soil Degradation
type: Concept

Soil Erosion
type: Concept

River Erosion and Accretion
type: Concept

Coastal Erosion and Accretion
type: Concept

Diarrhoeal Diseases
type: Concept

Waterborne Diseases
type: Concept

Cholera
type: Concept

Locust upsurge
type: Concept

Fungal Plant Disease
type: Concept

Human-Wildlife Conflict
type: Concept

Snakebite envenoming
type: Concept

Explosive Ordnance
type: Concept

Building Collapse
type: Concept

Structural Failure
type: Concept

Bridge Failure
type: Concept

Power Outage/ or Blackout
type: Concept

Water Supply Failure
type: Concept

Tunnel Failure
type: Concept

Drain and Sewer Flooding
type: Concept

Pollution
type: Concept

Soil Pollution
type: Concept

Mining Hazards
type: Concept

Rail Accident
type: Concept

Road Traffic Accident
type: Concept

Disaster and Conflict Waste
type: Concept

Landfilling
type: Concept

Waste Treatment Lagoons
type: Concept

Tailings
type: Concept

Runoff / Nonpoint Source Pollution
type: Concept

Land Degradation
type: Concept

Coastal Flooding
type: Concept
definition: Coastal flooding occurs from multiple sources, including storm surges, waves and swell, seiches, riverine and flash floods near the coast, tides, sea-level rise and tsunamis. It is most frequently the result of storm surges and high winds coinciding with high tides. The surge itself is the result of the raising of sea levels due to low atmospheric pressure. In particular configurations, such as major estuaries or confined sea areas, the piling up of water is amplified by a combination of the shallowing of the seabed and retarding of return flow (WMO, 2011; WMO, 2022).
alternative label: Estuarine Flooding
alternative label: Coastal inundation
note: Major deltas such as the Mississippi and Ganges are prone to coastal flooding when affected by hurricanes (cyclones). Another sensitive area is the southern North Sea in western Europe, as a result of particular tracks of winter depressions. If the surge takes place near the mouth of a river issuing into the sea, the river flow will be obstructed due to the surge, resulting in severe flooding over and near the coastal areas. Tsunamis resulting from sub-seabed earthquakes are a very specific cause of occasionally severe coastal flooding (WMO, 2011). Coastal flooding is largely a natural event, however, human influence on the coastal environment can exacerbate coastal flooding (Dawson et al., 2009). Extraction of water from groundwater reservoirs in the coastal zone can enhance subsidence of the land, increasing the risk of flooding (Nicholls, 2002). Seawater can flood the land via several paths: - Direct flooding: the sea height exceeds the elevation of the land, often where waves have not built up a natural barrier such as a dune system. - Overtopping of a barrier: the barrier may be natural or human- engineered, and overtopping occurs due to swell conditions during storms or high tides, often on open stretches of the coast. The height of the waves exceeds the height of the barrier, and water flows over the top of the barrier to flood the land behind it. Overtopping can result in high velocity flows that can erode significant amounts of the land surface, which can undermine defence structures (Gallien et al., 2011). - Breaching of a barrier: the barrier may be natural (sand dune) or human engineered (sea wall), and breaching occurs on open coasts exposed to large waves. Breaching is where the barrier is broken down or destroyed by waves allowing the seawater to extend inland and flood the area.
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: United Nations. (1982). United Nations Convention on the Law of the Sea (UNCLOS). Often referred to as the "constitution of the oceans," this convention provides a comprehensive framework for governing ocean space, including provisions to address coastal flooding and protect the marine environment.
scope note: ExplanatoryNote
  plain text: Flooding constitutes a particular challenge in low-lying areas such as deltas and coastal plains, and land subsidence caused by sediment deficits or ground water extraction can further exacerbate the problem.
  type: drivers
source: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
source: 58169-guidelines-on-implementation-of-a-coastal-inundation-forecasting-early-warning-system
was quoted from: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
was quoted from: 58169-guidelines-on-implementation-of-a-coastal-inundation-forecasting-early-warning-system
references: descriptionSource1
references: descriptionSource2
references: descriptionSource3
references: descriptionSource4
references: descriptionSource5
references: descriptionSource6
references: descriptionSource7
references: descriptionSource8
references: descriptionSource9
references: descriptionSource10
references: unclos e.pdf
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
references: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
references: https://library.wmo.int/records/item/37094-coastal-and-delta-flood-management
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was influenced by: https://library.wmo.int/records/item/37094-coastal-and-delta-flood-management
caused by: Loss of Mangroves
caused by: Tropical Cyclone
caused by: Fluvial (Riverine) Flooding
caused by: Rogue Wave
caused by: Seiche
caused by: Storm Surge
caused by: Storm Tides
caused by: Tsunami
caused by: Surface Rupture and Fissuring
causes: Soil Erosion
causes: Coastal Erosion and Accretion
causes: Estuarine (Coastal) Flooding
causes: Fluvial (Riverine) Flooding
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Leaks and Spills
causes: Safety Hazards Associated with Oil and Gas
causes: Rail Accident
causes: Road Traffic Accident
causes: Wastewater
causes: Marine Debris
causes: Tailings
created: 2023-06-07T08:40:00+00:00
modified: 2026-01-29T13:27:30+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Loss of Mangroves
type: Concept

Fluvial (Riverine) Flooding
type: Concept
definition: Overflowing by water of the normal confines of a watercourse or other body of water (WMO, 2012).
alternative label: Flood
alternative label: Flooding
note: Whereas floods are defined in hydrology as “a rise, usually 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), flooding represents the hazard associated with these peaks whenever the water overflows the normal confines of the water body. Fluvial flooding occurs over a wide range of river and catchment systems. Floods in river valleys occur mostly on flood plains or wash lands as a result of flow exceeding the capacity of the stream channels and spilling over the natural banks or artificial embankments (Fernandez, 2015).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: Fluvial (riverine) flooding primarily results from an extended precipitation event that occurs at, or upstream from, the affected area. It can also occur when traditional flood-control structures, such as levees and dikes, are overtopped or fail (NOAA, no date).
  type: drivers
scope note: ExplanatoryNote
  plain text: Whereas the general impacts of flooding have already been mentioned in the chapeau, riverine flooding is mostly associated with socio-economic impacts (such as disruption of activities, property and livelihood losses) rather than with direct mortality (drowning, traumatic events). Health impacts are generally more long-term, associated with contamination of freshwater resources, water-borne diseases, etc. Flooding of areas used for socio-economic activities produces a variety of negative impacts. The magnitude of adverse impacts depends on the vulnerability of the activities and population and the frequency, intensity and extent of flooding. Some of these factors include loss of lives and property, loss of livelihoods, decreased purchasing power and production power, mass migration, psychosocial effects, hindering of economic growth and development, and political implications (WMO, 2009). Control and monitoring measures of fluvial flood: Floods are important components of the natural hydrological regime. They are a major source of water; they flush pollutants and sediment from river networks. It is also natural for rivers to overtop their banks and occupy their flood plains. As a result, flooding can cause property damage and bring death and injury to many communities. While there is no evidence as yet that the frequency or magnitude of flooding has increased world-wide, flood-prone areas are becoming increasingly densely populated and thus more vulnerable. Consequently, a series of major flood disasters has occurred in recent years, with death and destruction being caused by such events on every continent (GWP, 2013). There is a need for an approach to flood management that improves the functioning of the river basin as a whole, recognising that floods have beneficial impacts and can never be fully controlled. Such an approach seeks to maximisze the net benefits from the use of floodplains and to minimise loss of life, subordinating flood loss reduction to the over…
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between fluvial flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: No Information Available
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring fluvial flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracks rainfall patterns, storm systems, and atmospheric conditions that influence river flooding. - Hydrological services monitors river levels, streamflow, soil moisture, and watershed conditions to assess flood potential. - Geophysical agencies studying terrain characteristics, sediment transport, and land subsidence that impact river flooding. - National, subnational, and local disaster management agencies responsible for monitoring river flood risks, issuing warnings, and coordinating emergency responses. - Health authorities assessing public health risks from waterborne diseases, contamination, and emergency medical response needs. - Engineers designing flood control infrastructure such as dams, levees, embankments, and drainage systems to mitigate river flooding. - Land use and urban planners integrating river flood risk assessments into zoning laws, watershed management, and sustainable development strategies. - Energy and utility companies monitoring flood risks to power plants, water treatment facilities, and critical infrastructure along rivers. - Researchers and academics, including hydrologists and climate scientists, studying river flow dynamics, climate change impacts, and flood forecasting models. | How is the Hazard Observed/Monitored/Forecast? | Fluvial (riverine) floods are monitored using river gauges, satellite imagery, and weather radar to track water levels, rainfall, and upstream flow conditions. Hydrologists analysze watershed characteristics, soi…
  type: monitoringEarlyWarning
source: https://library.wmo.int/viewer/35589/download
was quoted from: https://library.wmo.int/viewer/35589/download
references: apfm
references: https://procurement-notices.undp.org/view_file.cfm
references: 04-gwp-report-may-2013.pdf
references: understand
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
references: https://library.wmo.int/records/item/40434-integrated-flood-management
references: https://library.wmo.int/viewer/35589/download
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caused by: Dam Failure
caused by: Tropical Cyclone
caused by: Rain
caused by: Coastal Flooding
caused by: Estuarine (Coastal) Flooding
caused by: Ice-Jam Flooding Including Debris
caused by: Snowmelt Flooding
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Soil Erosion
causes: River Erosion and Accretion
causes: Coastal Flooding
causes: Surface Water Flooding
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Dam Failure
causes: Supply Chain Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Rail Accident
causes: Road Traffic Accident
causes: Wastewater
causes: Marine Debris
causes: Tailings
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-04T13:11:07+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Rogue Wave
type: Concept

Seiche
type: Concept

Storm Surge
type: Concept

Storm Tides
type: Concept

Tsunami
type: Concept

Surface Rupture and Fissuring
type: Concept

Estuarine (Coastal) Flooding
type: Concept
definition: Estuarine flooding is flooding over and near coastal areas caused by storm surges and high winds coincident with high tides, thereby obstructing the seaward river flow. Estuarine flooding can be caused by tsunamis in specific cases (WMO, 2011).
alternative label: Flood
alternative label: Flooding
alternative label: Coastal flooding
note: Estuaries are inlet areas of the coastline where the coastal tide meets a concentrated seaward flow of fresh water in a river. The interaction between the seaward flow of river water and landward flow of saline water during high tides may cause a build-up of water or an inland-moving tidal bore. Frequently, the funnel shape characteristic of many estuaries causes an increase in high water levels in the upper, narrowing reaches of the associated river. These types of floods are mostly experienced in deltaic areas of rivers along the coasts, for example, the mouths of the Ganges. They are more frequent and less severe in terms of inundated depth and area than flooding caused by storm surges (WMO, 2011).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: Storm surges and high winds coinciding with high tides are the most frequent cause of estuarine/coastal flooding. The surge itself is the result of the rising of sea levels due to low atmospheric pressure. In particular configurations, such as major estuaries or confined sea areas, the piling up of water is amplified by a combination of the shallowing of the seabed and retarding of return flow. Major deltas such as the Mississippi and Ganges are prone to this type of flooding when affected by hurricanes (cyclones). Another sensitive area is the southern North Sea in western Europe, owing to particular tracks of winter depressions. If the surge takes place near the mouth of a river issuing into the sea, the river flow will be obstructed due to the surge, resulting in severe flooding over and near the coastal areas. Tsunamis resulting from sub-seabed earthquakes are a very specific cause of occasionally severe coastal flooding (WMO, 2011). Also, estuarine flooding can happen in cases when riverine flooding (i.e. when the river is experiencing a significant freshwater flow) produces an overflow near the estuary/coastal zone. It is therefore difficult, as in the case of coastal flooding, to identify a single driver for estuarine flooding.
  type: drivers
scope note: ExplanatoryNote
  plain text: Floods are one of the most common hazards. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health issues (acute and long- term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases, as well as the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile fever) (WHO, no date). The longer-term health effects associated with a floods and related hazards, such as mould in homes, are less easily identified. They include effects due to displacement, destruction of homes, delayed recovery, and water shortages., (WHO, 2013).
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between estuarine flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: Effective risk management for estuarine flooding requires integrated approaches that combine structural measures, such as tidal barriers, embankments, and floodgates, with nature-based solutions like wetland restoration and mangrove protection, which buffer surge impacts. Accurate flood modelling, early warning systems, and land-use planning are essential to reduce vulnerability in densely populated estuarine zones. Long-term resilience also depends on adaptive governance frameworks that account for sea-level rise, climate change, and evolving socio-economic pressures. (UK Department of Environment, Food & Rural Affairs and Environment Agency, 2023)
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring estuarine flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological and hydrological services tracking rainfall, storm surges, river discharge, and tidal influences that contribute to estuarine flooding. - Oceanographic and marine agencies monitoring sea-level rise, tidal patterns, and sediment transport affecting estuarine flood risks. - National, subnational, and local disaster management agencies responsible for monitoring estuarine flood risks, issuing alerts, and coordinating emergency response. - Geophysical agencies studying land subsidence, tectonic activity, and coastal geomorphology that impact estuarine flood behaviour. - Health authorities assessing public health risks from saltwater intrusion, water contamination, and flood-related disease outbreaks. - Engineers designing flood defences such as tidal barriers, levees, drainage systems, and resilient infrastructure to mitigate estuarine flooding. - Land use and urban planners integrating estuarine flood risk assessments into zoning laws, wetland conservation, and urban development strategies. - Energy and utility companies monitoring risks to power plants, water supply systems, and communication networks in estuarine areas. - Researchers and academics, including hydrologists and climate scientists, studying the interactions between river flow, tides, and storm surges to improve flood forecasting and long-term adaptation strategies. | How is the Hazard Observed/Monitored/Forecast? | Estuarine (coastal) flooding is monitored using tide gauges, river flow sensors, satellite imagery, and…
  type: monitoringEarlyWarning
source: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
was quoted from: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
references: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
references: managing-future-flood-risk-and-thames-barrier-thames-estuary-2100
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was influenced by: https://apps.who.int/iris/handle/10665/108625
was influenced by: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
was influenced by: managing-future-flood-risk-and-thames-barrier-thames-estuary-2100
caused by: Surface Rupture and Fissuring
caused by: Rain
caused by: Coastal Flooding
caused by: Storm Surge
caused by: Storm Tides
caused by: Tsunami
causes: Fluvial (Riverine) Flooding
causes: Soil Erosion
causes: River Erosion and Accretion
causes: Coastal Erosion and Accretion
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Eutrophication
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Leaks and Spills
causes: Safety Hazards Associated with Oil and Gas
causes: Rail Accident
causes: Road Traffic Accident
causes: Wastewater
causes: Marine Debris
causes: Tailings
created: 2023-06-07T08:40:00+00:00
modified: 2026-01-29T14:00:40+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Critical Infrastructure Failure
type: Concept

Leaks and Spills
type: Concept

Safety Hazards Associated with Oil and Gas
type: Concept

Wastewater
type: Concept

Marine Debris
type: Concept

Eutrophication
type: Concept

Flash Flooding
type: Concept
definition: A flash flood is a flood of short duration with a relatively high peak discharge (WMO, 2021).
alternative label: Storm-driven flood
alternative label: Freshet
alternative label: Huayco
note: A flash flood is generally characterised by raging torrents after heavy rains, a dam or levee failure or a sudden release of water in a previously stopped passage (i.e., by debris or ice) that rips through riverbeds, urban streets, or mountain canyons, sweeping away everything in its path. Steep terrain tends to concentrate runoff into streams very quickly and is often a contributory factor. Changes in soil properties (e.g., burn areas from wildfires), hydrophobic or impervious soils, removal of surface vegetation, and excess runoff from warm rainfall on significant snowpack can also be important contributors (NOAA, no date a; AMS, 2017).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: The intensity of the rainfall, the location and distribution of the rainfall, the land use and topography, vegetation types and growth/density, soil type, and soil water-content all determine how quickly flash flooding may occur, and influence where it may occur (NOAA, no date b).
  type: drivers
scope note: ExplanatoryNote
  plain text: lash floods account for approximately 85% of flooding cases and have the highest mortality rate (defined as the number of deaths per number of people affected) among different classes of flooding (e.g., riverine, coastal). Flash floods are among the world’s deadliest natural hazards and have significant social, economic and environmental impacts (WMO, 2019). Health impacts from floods, including flash floods: As mentioned in the chapeau, the effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health issues (acute and long- term). Flash flooding is usually associated with trauma and drowning in terms of mortality and injuries. While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards (see chemical HIPs) and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-bor…
  type: impacts
scope note: ExplanatoryNote
  plain text: A flash flood is a flood that begins within 6 hours, and often within 3 hours, of a heavy rainfall (NOAA, no date b). Flash floods are highly localised in space: they are restricted to basins of a few hundred square kilometres or less. They are also restricted in time: response times not exceeding a few hours or even less. This means very little time for warning (NOAA, no date b). Flash flood hazard measurement and modelling requires considering more environmental factors, regularly monitored: topographic parameters (average slope, slope range and valley density for the catchment), soil and surface parameters (surface runoff, infiltration and interception: soil depth, physical soil type, the ratio of barren/ vegetation-covered surfaces), and hydrological parameters (precipitation, consecutive rainy days, etc.) (Liu and Smedt, 2005).
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between flash flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: Flash floods are a major natural hazard throughout the world. Flash floods are the number one killer among all weather-related hazards. A vast majority of deaths from flash floods, as high as 90% in tropical countries, are due to drowning from victims being caught by rapidly rising waters (Smith, 1992). Predicting flash floods requires accurate detection and estimation of rainfall events, which are typically intense and very localised. Operational prediction methods include flash flood monitoring and prediction algorithms (FFMPA) used in Europe and the United States. FFMPA alerts forecasters when flash flooding is imminent based on radar-estimated rainfall amounts compared to hydrologic model-based rainfall thresholds. Advances in forecasting convective rainstorms help to improve the performance of FFMPA by providing a longer lead time of impending flash floods (Hong et al., 2013). Reducing societal exposure to flash floods is key to any mitigation measure. The combination of non-structural measures and small-scale structural measures could be more effective in managing flash flood risk. There are many non-structural measures that can reduce the impact of floods, such as land-use planning, building construction codes, soil management, acquisition policies, insurance and risk transfer, awareness raising, public information, emergency system, and recovery plans. Structural activities, including property protection such as relocation and reinforcement, and structural engineering projects such as levees, diversions, and channel improvements, are some of the actions that mitigate the societal impacts of flash floods (Colombo et al., 2002). Flash floods differ from river floods in various ways. Notably they manifest and dissipate in less time and occur in more condensed spatial areas. These factors make their forecasting a unique challenge compared to traditional flood forecasting approaches. In this regard, the World Meteorological Organization has launched the Flash Flo…
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring flash flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological and Hydrological services track heavy rainfall, storm systems, and atmospheric conditions that contribute to flash floods. Hydrological organiszations monitor river levels, soil moisture, and runoff to assess flash flood potential. - National, subnational, and local disaster management agencies responsible for monitoring flash flood risks, issuing alerts, and coordinating emergency response efforts. - Geophysical agencies studying land stability, terrain characteristics, and changes that affect water flow during extreme rainfall events. - Health authorities evaluating risks to public safety, including waterborne diseases, infrastructure failure, and emergency medical response. - Engineers designing flood control systems, stormwater drainage infrastructure, and protective barriers to mitigate flash flood impacts. - Land use and urban planners integrating flash flood risk assessments into zoning laws, watershed management, and urban development planning. - Energy and utility companies monitoring risks to power stations, water supply systems, and communication networks in flood-prone areas. - Researchers and academics, including hydrologists and climate scientists, studying rainfall-runoff relationships, flash flood forecasting models, and climate change impacts. - Organiszations and community representatives engaged in flash flood preparedness, public education, and local early warning dissemination. | How is the Hazard Observed/Monitored/Forecast? | Flash floods are monitored using w…
  type: monitoringEarlyWarning
source: https://library.wmo.int/records/item/35631-technical-regulations-volume-iii-hydrology
was quoted from: https://library.wmo.int/records/item/35631-technical-regulations-volume-iii-hydrology
references: Flash flood
references: source
references: descriptionSource3
references: descriptionSource4
references: flood and flash
references: FlashFloodingDefinition
references: descriptionSource7
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
references: ffgs
was influenced by: Flash flood
was influenced by: source
was influenced by: descriptionSource3
was influenced by: descriptionSource4
was influenced by: flood and flash
was influenced by: FlashFloodingDefinition
was influenced by: descriptionSource7
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
was influenced by: ffgs
caused by: Thunderstorm
caused by: Tropical Cyclone
caused by: Rain
caused by: Glacial Lake Outburst Flooding
caused by: Ice-Jam Flooding Including Debris
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Eutrophication
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
causes: Insect Pest Infestations
causes: Coastal Flooding
causes: Surface Water Flooding
causes: Lahars
causes: Gravitational Mass Movement (‘Landslide’)
causes: Rock, debris and earth spreads (including landscape creep)
causes: Debris and earth (mud)flows and rock avalanches
causes: Rock, debris and earth (mud) slide
causes: Soil Erosion
causes: River Erosion and Accretion
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Supply Chain Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Leaks and Spills
causes: Rail Accident
causes: Road Traffic Accident
causes: Wastewater
created: 2023-06-07T08:40:00+00:00
modified: 2026-01-29T14:23:17+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Glacial Lake Outburst Flooding
type: Concept
definition: 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).
alternative label: GLOF
note: The term glacial lake outburst flood (GLOF) is used here to refer to the catastrophic release of a water reservoir that has formed either at the side, in front, within, beneath or on the surface of a glacier. Dam structures that impound the water reservoir may be composed primarily of glacial ice, morainic debris, or bedrock (GAPHAZ, 2017). GLOFs are characterised by extreme peak discharges, often several times in excess of the maximum discharges of hydrometeorological induced floods, with an exceptional erosion/transport potential. They can therefore turn into flow-type movements, such as GLOF-induced debris flow (Emmer, 2017; UN-SPIDER, no date).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: Key overarching determinants of GLOF susceptibility and the resulting event magnitude are the size of the glacier lake, the outburst mechanism (and related hydrograph), and the characteristics of the downstream torrent (determined by channel inclination and debris availability). Ice-dammed lakes can develop at the margin of an advancing (or surging) glacier, when side -valleys or depressions at the side of the glacier become truncated and blocked. Many such lakes formed in high mountain regions during the Last Glacial Maximum and more recently during and following the Little Ice Age. Over time, as the glaciers retreat, the support of the ice dam is removed, and the lake may drain catastrophically or remain trapped behind lateral moraines of the former glacier (GAPHAZ, 2017; UN-SPIDER, no date). Additionally, as glaciers retreat, the surface areas of glacial lakes increase. Debuttressing effects and landslides, even ice avalanches, are frequent drivers (Cook et al, 2018).
  type: drivers
scope note: ExplanatoryNote
  plain text: Notwithstanding the general considerations on flooding impacts contained in the chapeau, GLOFs impacts are similar to those of flash floods The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning, to infectious diseases and mental health problems (acute and long-term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile Fever) (WHO, no date). The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delayed recovery and water shortages (WHO, 2013).
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between glacial lake outburst flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: Various schemes have been proposed for assessing the susceptibility of glacial lakes to an outburst flood, mostly drawing on remotely sensed information to characterise, semi-quantitatively, the cryospheric environment, lake and dam area, and other geotechnical and geomorphic characteristics of the upstream catchment area of the lake. The potential for unstable rock and/or ice to impact into a lake can be determined using worst-case runout distances. Assessment approaches have mostly been developed and tailored towards regional implementation, especially for moraine- dammed lakes, for which McKillop and Clague (2007) gave a comprehensive overview of many of the relevant susceptibility factors that may condition or trigger an outburst event (GAPHAZ, 2017).
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring glacial lake outburst flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracking temperature fluctuations, precipitation, and climate patterns influencing glacial melt and lake stability. - Hydrological services monitoring glacial lake water levels, river discharge, and downstream flood risks. - National, subnational, and local disaster management agencies responsible for monitoring GLOF risks, issuing alerts, and coordinating emergency response efforts. - Geological and geophysical agencies studying glacial moraine stability, terrain changes, and seismic activity that could trigger a GLOF. - Glaciological research institutions analysing glacier retreat, ice dynamics, and lake formation to assess long-term flood risks. - Remote sensing and space agencies using satellite imagery, LiDAR, and drones to monitor glacial lakes, detect changes, and map flood-prone areas. - Health authorities assessing public safety risks from waterborne diseases, infrastructure collapse, and emergency medical needs. - Engineers and infrastructure agencies designing early warning systems, flood barriers, and drainage channels to mitigate GLOF impacts. - Land use and urban planners incorporating GLOF risk assessments into zoning laws, infrastructure placement, and disaster preparedness strategies. - Energy and utility companies monitoring risks to hydropower stations, water supply systems, and other critical infrastructure in glacial regions. - Researchers and academics, including hydrologists and climate scientists, studying glacial dynamics, climate ch…
  type: monitoringEarlyWarning
source: https://oxfordre.com/naturalhazardscience/view/10.1093/acrefore/9780199389407.001.0001/acrefore-9780199389407-e-275
was quoted from: https://oxfordre.com/naturalhazardscience/view/10.1093/acrefore/9780199389407.001.0001/acrefore-9780199389407-e-275
references: https://oxfordre.com/naturalhazardscience/view/10.1093/acrefore/9780199389407.001.0001/acrefore-9780199389407-e-275
references: 321530454 Assessment of Glacier and Permafrost Hazards in Mountain Regions Technical Guidance Document
references: science.aat4981
references: descriptionSource4
references: glacial-lake-outburst
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
was influenced by: https://oxfordre.com/naturalhazardscience/view/10.1093/acrefore/9780199389407.001.0001/acrefore-9780199389407-e-275
was influenced by: 321530454 Assessment of Glacier and Permafrost Hazards in Mountain Regions Technical Guidance Document
was influenced by: science.aat4981
was influenced by: descriptionSource4
was influenced by: glacial-lake-outburst
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
caused by: Gravitational Mass Movement (‘Landslide’)
caused by: Rain
caused by: Thaw
causes: Gravitational Mass Movement (‘Landslide’)
causes: River Erosion and Accretion
causes: Flash Flooding
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Dam Failure
causes: Supply Chain Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Leaks and Spills
causes: Safety Hazards Associated with Oil and Gas
causes: Rail Accident
causes: Road Traffic Accident
causes: Wastewater
causes: Marine Debris
causes: Tailings
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-04T13:35:39+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Ice-Jam Flooding Including Debris
type: Concept
definition: An ice-jam flood including debris is defined as an accumulation of shuga including ice cakes, below ice cover. It is broken ice in a river which causes a narrowing of the river channel, a rise in water level and local floods (WMO, 2012). Shuga is defined as the accumulation of spongy white ice lumps, a few centimetres across, formed from grease ice or slush, and sometimes from anchor ice rising to the surface (WMO, 2012).
alternative label: Flash Flood
alternative label: Flooding
note: Ice-jam flooding is caused by an accumulation of ice in a river, stream or other flooding source that reduces the cross-sectional area available to carry the flow and forces an increase in water-surface elevation (WMO, 2012).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: In rivers/streams that experience seasonal ice formation and melt, if the melting is more rapid upstream than downstream, ice floes can accumulate in rivers, forming constrictions and damming flows, causing river levels to rise upstream of the ice jam. A sudden release of the ‘ice jam’ can cause a flood wave similar to that caused by a dam break, to move downstream. Both meltwater and heavy rainfall in steep areas can cause landslips and debris flows. As the debris picked up by rivers moves downstream, major constrictions can build up. When these build-ups collapse or are breached, severe flooding can result. These phenomena are difficult to predict (WMO, 2011; FEMA, 2018).
  type: drivers
scope note: ExplanatoryNote
  plain text: Floods are one of the most common hazards. In line with the general impacts defined in the chapeau, ice-jam flooding can have both a slow onset (when flooding occurs upstream to the ice jam) and an abrupt occurrence (similar to a dam break) when the ice jam collapses, leading to a flash-flood-like impact downstream. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning, to infectious diseases and mental health problems (acute and long- term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile Fever) (WHO, no date). The longer-term health effects associated with a flood are less easily identified. They include effects due to…
  type: impacts
scope note: ExplanatoryNote
  plain text: Not applicable.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between ice-jam flooding, including debris, and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: No Information Available
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring ice-jam flooding, including debris. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracking temperature fluctuations, precipitation, and freeze-thaw cycles that contribute to ice jam formation. - Hydrological services monitoring river levels, ice thickness, flow velocity, and debris accumulation in water channels. - Geological and geophysical agencies studying riverbed morphology, sediment transport, and terrain conditions affecting ice jam development. - National, subnational, and local disaster management agencies responsible for monitoring ice-jam flood risks, issuing warnings, and coordinating emergency response. - Health authorities assessing public safety risks, including waterborne diseases, hypothermia exposure, and emergency medical needs. - Engineers and water resource management agencies designing ice control structures, flood defences, and debris removal strategies. - Land use and urban planners incorporating ice-jam flood risk assessments into zoning laws, infrastructure siting, and watershed management. - Energy and utility companies monitoring risks to hydropower plants, bridges, pipelines, and other infrastructure vulnerable to ice and debris blockages. - Researchers and academics, including hydrologists and climate scientists, studying ice jam formation, flood forecasting, and climate change impacts on freeze-thaw dynamics. - Environmental organiszations and conservation groups working on river ecosystem management, ice jam mitigation, and debris control strategies. | How is the Hazard Observed/Monitored/Forecast? | Ic…
  type: monitoringEarlyWarning
source: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
was quoted from: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
references: Ice Jam Guidance Feb 2018.pdf
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
references: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
references: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
was influenced by: Ice Jam Guidance Feb 2018.pdf
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
was influenced by: https://library.wmo.int/records/item/35881-manual-on-flood-forecasting-and-warning
was influenced by: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
caused by: Rain
caused by: Thaw
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Flash Flooding
causes: Fluvial (Riverine) Flooding
causes: Surface Water Flooding
causes: Soil Erosion
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Dam Failure
causes: Supply Chain Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Rail Accident
causes: Road Traffic Accident
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-05T07:56:27+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Insect Pest Infestations
type: Concept

Surface Water Flooding
type: Concept
definition: Surface water flooding is that part of the rain which remains on the ground surface during rain and either runs off or infiltrates after the rain ends, not including depression storage (WMO, 2012).
alternative label: Surface detention
alternative label: Depression storage
alternative label: Surface retention
note: Surface water flooding is caused when the volume of rainwater falling does not drain away through the existing drainage systems or soak into the ground but lies on or flows over the ground instead. This type of flooding is usually short-lived and associated with heavy downpours of rain, thunderstorms etc. (NFU, 2019). The UK Government provides a real time flood information service which is easily accessible (UK Government, no date).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: Floods tend to be caused by a number of natural events such as rain from slow- moving or stationary low-pressure areas, thunderstorms, and tropical cyclones. The amount and duration of the rainfall, soil type and saturation, geography and whether it is an urban area can affect the magnitude and impacts of the flooding. Flooding can occur at the place of a heavy rain event or far downstream away from the causal rain event. Flooding can also be caused by other factors such as storm surges, tsunamis, ice jams, glacial lake outbursts, as well as being human influences such as dam bursts, improper land use planning, etc. (Geoscience Australia, no date).
  type: drivers
scope note: ExplanatoryNote
  plain text: This type of flooding’s impacts are very similar to those of groundwater flooding or ponding. Floods are one of the most common hazards. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long- term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile fever) (WHO, no date). The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delayed recovery and water shortages (WHO, 2013).
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between surface water flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: No Information Available
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring surface water flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracking intense rainfall, storm systems, and weather conditions that contribute to surface water flooding. - Hydrological services monitoring runoff patterns, soil moisture levels, and drainage system capacity to assess flood risks. - Geological and geophysical agencies studying land characteristics, permeability, and topography that influence water pooling and flood extent. - National, subnational, and local disaster management agencies responsible for monitoring surface water flooding, issuing warnings, and coordinating emergency response. - Municipal and urban drainage authorities managing stormwater infrastructure, retention basins, and drainage networks to prevent flooding. - Health authorities assessing public health risks from stagnant water, waterborne diseases, and sanitation issues caused by surface water flooding. - Engineers and infrastructure agencies designing flood mitigation measures such as permeable pavements, stormwater management systems, and urban drainage improvements. - Land use and urban planners incorporating surface water flood risk assessments into zoning regulations, sustainable development plans, and watershed management. - Energy and utility companies monitoring flood risks to underground electrical grids, water treatment plants, and transportation networks. - Researchers and academics, including hydrologists and urban planners, studying urban flooding patterns, climate change impacts, and flood forecasting techniques. - Environmental …
  type: monitoringEarlyWarning
source: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
was quoted from: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
references: flood
references: ea-maps-show-risk-from-surface-water-flooding
references: alerts-and-warnings
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
was influenced by: flood
was influenced by: ea-maps-show-risk-from-surface-water-flooding
was influenced by: alerts-and-warnings
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
caused by: Dam Failure
caused by: Critical Infrastructure Failure
caused by: Surface Rupture and Fissuring
caused by: Rain
caused by: Fluvial (Riverine) Flooding
caused by: Ice-Jam Flooding Including Debris
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Building Collapse
causes: Structural Failure
causes: Bridge Failure
causes: Dam Failure
causes: Supply Chain Failure
causes: Critical Infrastructure Failure
causes: Drain and Sewer Flooding
causes: Leaks and Spills
causes: Safety Hazards Associated with Oil and Gas
causes: Rail Accident
causes: Road Traffic Accident
causes: Wastewater
causes: Marine Debris
causes: Tailings
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-05T12:37:16+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Rock, debris and earth spreads (including landscape creep)
type: Concept

Supply Chain Failure
type: Concept

Snowmelt Flooding
type: Concept
definition: A snowmelt flood is a significant flood rise in a river caused by the melting of snowpack accumulated during the winter (WMO, 2012).
alternative label: Flood
alternative label: Flooding
alternative label: Melt-induced flooding
alternative label: Snowmelt-runoff floods
note: In upland and high-latitude areas where extensive snow accumulates over winter, the spring thaw produces meltwater runoff. If temperature increases are rapid, the rate of melting may produce floods, which can extend to lower parts of the river systems. The severity of meltwater floods will increase if the thaw is accompanied by heavy rainfall and can be further exacerbated if the subsoil remains frozen. Although a seasonal occurrence, where major snowfields exist in headwaters, which may produce beneficial flooding in downstream areas, severe effects can occur on smaller scales, especially in areas subject to changes between cold and warmer rainy winter weather (USGS, no date) and steep slopes.
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: High soil moisture conditions prior to snowmelt, frozen ground, heavy snow cover, widespread heavy rain during the melt period, and rapid snowmelt (unseasonably warm temperatures, high humidity, rainfall, etc.) (NOAA, no date).
  type: drivers
scope note: ExplanatoryNote
  plain text: Notwithstanding the general considerations provided in the chapeau about floods, snowmelt floods can have similar impacts to flash floods (in the upper part of the catchment, combined with a fast thaw) or riverine floods (downstream to the melting area). The effect of snowmelt on potential flooding, mainly during the spring, causes concern for many people around the world. Besides flooding, rapid snowmelt can trigger landslides and debris flows. In combination with specific weather conditions, such as excessive rainfall on melting snow, for example, it may even be a major cause of floods (USGS, no date). Health impacts from floods: Floods are one of the most common hazards. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long-term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of co…
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between snowmelt flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: Cryosphere observation is needed to monitor the snowmelt rate, combined with traditional streamflow observation and flood forecasting techniques downstream to the area experiencing snowmelt. The Flash Flood Guidance System (FFGS) of the World Meteorological Organization takes into account estimated precipitation from several sources, such as satellites, radar as available, and gauges as available to be input into a snow model (SNOW -17) which estimates snow water equivalent (SWE) and melt that are input into the Sacramento-soil moisture accounting model (SAC-SMA) to estimate upper soil moisture (soil water deficit). SNOW-17 uses air temperature as an index to determine energy exchange across the snow-air interface. In addition to temperature, the only other input variable needed to run the model is precipitation. Air temperature is also used to estimate snowmelt. SWE is referred to as the depth of water produced if a snow cover is completely melted on a horizontal surface. The SWE product generated by FFGS is a direct output of the SNOW-17 accumulation and ablation model. Melt is the estimate of ablation due to melt processes and is the direct output of the SNOW-17 model (WMO, 1999).
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring snowmelt flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracking temperature fluctuations, precipitation, and weather patterns influencing snowmelt rates. - Hydrological services monitoring snowpack levels, river flows, soil moisture, and groundwater recharge to assess flood risks. - Geological and geophysical agencies studying terrain characteristics, soil permeability, and land stability that affect snowmelt runoff. - National, subnational, and local disaster management agencies responsible for monitoring snowmelt flood risks, issuing alerts, and coordinating emergency response efforts. - Health authorities assessing public health risks from floodwater contamination, infrastructure failures, and emergency medical needs. - Engineers and water resource management agencies designing and maintaining flood control structures, reservoirs, and drainage systems to manage excess runoff. - Land use and urban planners incorporating snowmelt flood risk assessments into zoning laws, watershed management, and urban development strategies. - Energy and utility companies monitoring flood risks to hydropower stations, water treatment facilities, and critical infrastructure in snowmelt-prone regions. - Researchers and academics, including hydrologists and climate scientists, studying snowmelt dynamics, climate change impacts, and flood forecasting models. - Environmental organisations and conservation groups working on watershed management, reforestation, and ecosystem-based flood mitigation strategies. | How is the Hazard Observed/Monitored…
  type: monitoringEarlyWarning
source: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
was quoted from: https://library.wmo.int/records/item/35589-international-glossary-of-hydrology
references: flooding factsheet.pdf
references: qt-science center objects
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
was influenced by: flooding factsheet.pdf
was influenced by: qt-science center objects
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
caused by: Thaw
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Drain and Sewer Flooding
causes: Rail Accident
causes: Road Traffic Accident
causes: Fluvial (Riverine) Flooding
causes: Ponding (Drainage) Flooding
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-05T09:42:44+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Thaw
type: Concept

Groundwater Flooding
type: Concept
definition: A groundwater flood is the emergence of groundwater at the ground surface away from perennial river channels or the rising of groundwater into man-made ground, under conditions where the ‘normal’ ranges of groundwater level and groundwater flow are exceeded (BGS, 2010).
alternative label: Flood
alternative label: ponding
note: Groundwater flooding is a different type of hazard than river or surface water flooding in that the onset is not an immediate process where water suddenly encroaches areas not normally inundated. In contrast, the water levels within permeable strata will gradually rise over time giving rise to the formation of springs and ephemeral streams, areas of ponding, surcharging of wells and boreholes, and water ingress in basements, tunnels, or other below- ground structures. Water levels can remain high for many weeks or even months, depending on the nature of the underlying strata and meteorological and hydrological conditions (WMO, 2007). Groundwater flooding occurs when the natural underground drainage system cannot drain rainfall away quickly enough, causing the water table to rise above the ground surface. It can pose a significant flood hazard for many rural communities, and its increased frequency in recent years highlights the need for further research (Geological Survey Ireland, 2021). Both perched groundwater and periodic springs can be causes of floods: - Perched groundwater: a groundwater body, generally of moderate dimensions, supported by a relatively impermeable stratum and which is located between a water table and the ground surface (WMO, 2012). - Periodic spring: a spring flowing irregularly in relation to the hydrological regime of groundwater or in connection with karstic conditions is generally known as a periodic or seasonal spring (WMO, 2012).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: European Union Floods Directive (2007/60/EC): The Directive on the assessment and management of flood risks entered into force on 26 November 2007. It requires member states to assess if all water courses and coastlines are at risk from flooding, to map the flood extent and assets and humans at risk in these areas, and to take adequate and coordinated measures to reduce this flood risk. The Directive also reinforces the rights of the public to access this information and to have a say in the planning process (European Commission, 2007).
scope note: ExplanatoryNote
  plain text: No Information Available
  type: drivers
scope note: ExplanatoryNote
  plain text: Floods are one of the most common hazards. Due to their usually slow onset, groundwater flooding’s main health effects are related to water-borne and vector-borne diseases. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long- term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases, as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile fever) (WHO, no date). The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delayed recovery and water shortages (WHO, 2013).
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between groundwater flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: Effective risk management involves continuous groundwater monitoring, hydrological modelling, and restricting development in high-risk zones. Sustainable drainage systems and early warning mechanisms can help mitigate impacts, particularly for infrastructure, basements, and agricultural land. Long-term resilience depends on coordinated planning among local authorities, environmental agencies, and water management institutions. (Environment Agency, 2012)
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring groundwater flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracking prolonged rainfall, snowmelt, and climate patterns that contribute to rising groundwater levels. - Hydrological services monitoring groundwater tables, soil moisture levels, and aquifer recharge rates to assess flood potential. - Geological and geophysical agencies studying land subsidence, soil permeability, and underground water flow dynamics that influence groundwater flooding. - National, subnational, and local disaster management agencies responsible for monitoring groundwater flooding risks and coordinating emergency response. - Health authorities assessing public health risks from contaminated groundwater, waterborne diseases, and sanitation issues. - Engineers and water resource management agencies designing drainage systems, flood mitigation structures, and sustainable groundwater management strategies. - Land use and urban planners integrating groundwater flood risk assessments into zoning laws, infrastructure planning, and water conservation strategies. - Energy and utility companies monitoring groundwater flooding risks to underground infrastructure, including power stations, tunnels, and water treatment plants. - Researchers and academics, including hydrologists and environmental scientists, studying groundwater behaviour, long-term aquifer changes, and climate impacts on subsurface flooding. - Environmental organisations and conservation groups working on natural groundwater management solutions, wetland restoration, and sustainable water usage.…
  type: monitoringEarlyWarning
source: groundwater flooding.html
was quoted from: groundwater flooding.html
references: descriptionSource1
references: descriptionSource2
references: What-is-groundwater-flooding.aspx
references: descriptionSource4
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
references: https://library.wmo.int/records/item/37079-conducting-flood-loss-assessments
references: 35589-international-glossary-of-hydrology
was influenced by: descriptionSource1
was influenced by: descriptionSource2
was influenced by: What-is-groundwater-flooding.aspx
was influenced by: descriptionSource4
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
was influenced by: https://library.wmo.int/records/item/37079-conducting-flood-loss-assessments
was influenced by: 35589-international-glossary-of-hydrology
caused by: Surface Rupture and Fissuring
caused by: Tropical Cyclone
caused by: Rain
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Lahars
causes: Sinkhole
causes: Soil Erosion
causes: Ponding (Drainage) Flooding
causes: Drain and Sewer Flooding
causes: Rail Accident
causes: Road Traffic Accident
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-04T13:59:13+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

Sinkhole
type: Concept

Ponding (Drainage) Flooding
type: Concept
definition: A ponding flood is a flood that results from rainwater ponding at or near the point where it falls because it is falling faster than the drainage system (natural or man-made) can carry it away (WMO, 2006).
alternative label: Pluvial Flood
alternative label: Drainage flood
alternative label: Surface retention
alternative label: Waterlogging
note: The Federal Emergency Management Agency (FEMA) refers to the term “ponding hazard”, defined as “a flood hazard that occurs in flat areas when there are depressions in the ground that collect "ponds" of water” (FEMA, 2020).
has part: diagram1
broader: Flooding
broader: Meteorological and Hydrological
broader: Water-related
in scheme: hips
publisher: UNDRR, ISC, and contributors
relation: Sendai Framework for Disaster Risk Reduction 2015-2030.
scope note: ExplanatoryNote
  plain text: Ponding flooding, also known as waterlogging, is primarily driven by a combination of intense or prolonged rainfall that exceeds both the soil’s infiltration capacity and the limits of urban drainage infrastructure. In cities, the widespread replacement of permeable land with impervious surfaces such as asphalt and concrete significantly increases surface runoff, leading to rapid accumulation of water during storms (Environment Agency, 2011). This effect is particularly severe in topographic depressions—natural or human-made—where water tends to collect, including in areas of land subsidence or reclaimed terrain. Inadequate or ageing drainage systems, often designed using outdated precipitation data, struggle to cope with current rainfall extremes and are prone to failure (UN-Habitat, 2020). Additionally, human-induced changes such as wetland loss, which eliminates natural water retention, and modifications to landforms from agriculture or construction can disrupt historical drainage pathways and increase vulnerability (BGS, 2023). These drivers, taken together, contribute to the rising incidence and severity of ponding flooding, particularly in rapidly urbanising regions.
  type: drivers
scope note: ExplanatoryNote
  plain text: Floods are one of the most common hazards. Similar to groundwater flooding, and notwithstanding the general impacts of flooding provided in the chapeau, due to their usually slow onset, ponding flood’s main health effects are related to water-borne and vector-borne diseases. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long- term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile Fever) (WHO, no date). The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delaye…
  type: impacts
scope note: ExplanatoryNote
  plain text: Not identified.
  type: metrics
scope note: ExplanatoryNote
  plain text: The figure below summarises common interactions between ponding flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
  type: multiHazardContext
scope note: ExplanatoryNote
  plain text: No Information Available
  type: riskManagement
scope note: ExplanatoryNote
  plain text: The section above and the table below offer an overview of monitoring ponding flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological services tracking heavy rainfall, storm intensity, and weather conditions that contribute to drainage system overloads. - Hydrological services monitoring soil moisture, runoff patterns, and water accumulation in urban and rural areas. - Geological and geophysical agencies studying land permeability, topography, and ground stability that affect water drainage. - Municipal and urban drainage authorities managing stormwater infrastructure, sewer systems, and flood mitigation efforts. - National, subnational, and local disaster management agencies responsible for monitoring drainage-related flood risks, issuing warnings, and coordinating emergency response. - Health authorities assessing public health risks related to stagnant water, mosquito-borne diseases, and water contamination. - Engineers and infrastructure agencies designing and maintaining storm drains, retention basins, and permeable surfaces to manage excess water. - Land use and urban planners integrating drainage flood risk assessments into zoning laws, building regulations, and sustainable urban development. - Energy and utility companies monitoring flood risks to underground electrical grids, sewage treatment plants, and water supply systems. - Researchers and academics, including hydrologists and urban planners, studying urban flooding, drainage efficiency, and climate change impacts on stormwater management. - Environmental organisations and conservation groups promoting green infrastructure, wetland restoration, and …
  type: monitoringEarlyWarning
source: https://library.wmo.int/records/item/35631-technical-regulations-volume-iii-hydrology
was quoted from: https://library.wmo.int/records/item/35631-technical-regulations-volume-iii-hydrology
references: home.html
references: groundwater-flooding
references: https://www.fema.gov/about/glossary/ponding-hazard
references: wcr 2020 report.pdf
references: https://iris.who.int/handle/10665/232690
references: https://apps.who.int/iris/handle/10665/108625
was influenced by: home.html
was influenced by: groundwater-flooding
was influenced by: https://www.fema.gov/about/glossary/ponding-hazard
was influenced by: wcr 2020 report.pdf
was influenced by: https://iris.who.int/handle/10665/232690
was influenced by: https://apps.who.int/iris/handle/10665/108625
caused by: Groundwater Flooding
caused by: Snowmelt Flooding
causes: Runoff / Nonpoint Source Pollution
causes: Land Degradation
causes: Groundwater Flooding
causes: Soil Erosion
causes: Drain and Sewer Flooding
causes: Rail Accident
causes: Road Traffic Accident
causes: Diarrhoeal Diseases
causes: Waterborne Diseases
created: 2023-06-07T08:40:00+00:00
modified: 2026-02-05T08:26:14+00:00
rights: Creative Commons CC BY 4.0
version info: 2025 update; https://www.undrr.org/publication/2025-update-undrr-isc-hazard-information-profiles-hips

ExplanatoryNote
plain text: More people are impacted by floods than by any other hazard. Year on year floods hit various regions around the world, with developing countries most at risk. Almost 2 million people worldwide live in flooding-prone coastal regions. Floods can carry devastating consequences, causing mortality and significant economic loss and damage, with flash floods being the most dangerous due to their speed and destructive power (UNDRR, no date; WMO, 2025; NOAA, no date b). Health impacts from floods: The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long-term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of communicable diseases (WHO, no date). The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delaye…
type: impacts

ExplanatoryNote
plain text: Key flooding metrics, such as flood depth and flow velocity, are usually combined with other variables, such as flooding arrival time, flooding duration, sediment load, contamination levels, and so on, to determine flood hazard indicators (Maranzoni et al., 2022). However, these indicators and metrics may vary across different types of flooding. For example: - Coastal Flood: The extent and magnitude of coastal flooding is a function of the elevation inland flood waters penetrate, which is controlled by the topography of the coastal land exposed to flooding and coastal flooding-related drivers (Bell et al., 2017). - Flash Flood: A flash flood is a flood that begins within 6 hours, and often within 3 hours, of a heavy rainfall (NOAA, no date a).
type: metrics

ExplanatoryNote
plain text: The figure below summarises common interactions between flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
type: multiHazardContext

ExplanatoryNote
plain text: Climate variability and change is giving rise to increasingly frequent and intense flood events, with changes in land use, ecosystem degradation and increased population pressure on flood-prone areas exacerbating flood risk worldwide and aggravating flood-related impacts (UNDRR, no date; WMO, 2025). Integrated Flood Management (IFM) encourages “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” WMO, 2009. An example of an initiative promoting an IFM approach is the Associated Programme on Flood Management (APFM), a joint initiative between the World Meteorological Organization (WMO) together with the Global Water Partnership. The APFM “promotes the concept of IFM to maximize net benefits from the use of floodplains and minimize the loss of life and impacts. As such, it provides tools and publications to support flood management” (WMO, 2025). Aside from risk management, there are several measures that can support flood-related risk reduction: - “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” (UNDRR, no date).
type: riskManagement

ExplanatoryNote
plain text: The section above and the table below offer an overview of monitoring flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological service tracking rainfall, storms, and weather patterns that contribute to flooding. - Hydrological service monitoring river levels, groundwater saturation, and watershed conditions to assess flood risks. - Oceanographic and marine agencies studying sea-level rise, storm surges, and coastal flooding risks. - Geophysical agencies analysing land stability, soil conditions, and factors like land subsidence that impact flood behaviour. - Health authorities evaluating public health risks from floodwater contamination, waterborne diseases, and emergency medical needs. - Engineers and infrastructure agencies designing and maintaining flood control systems such as levees, dams, drainage networks, and stormwater management systems. - Land use and urban planners integrating flood risk assessments into zoning laws, building regulations, and sustainable development strategies. - Energy and utility companies monitoring flood risks to power plants, water treatment facilities, and communication networks. - Researchers and academics, including hydrologists and climate scientists, studying flood forecasting, climate change impacts, and long-term risk reduction strategies. - Environmental organiszations and conservation groups working on nature-based flood mitigation solutions, such as wetland restoration and watershed management. | How is the Hazard Observed/Monitored/Forecast? | Flooding is monitored using weather radar, rain gauges, river sensors, and satellites that track rainfall, water levels, and so…
type: monitoringEarlyWarning

ExplanatoryNote
plain text: Coastal flooding can result in considerable economic losses and casualties. Moreover, coastal flooding can result in a wide range of environmental impacts on different spatial and temporal scales. Flooding can destroy coastal habitats such as coastal wetlands and estuaries and can erode dune systems (Hunt and Watkiss, 2011).
type: impacts

ExplanatoryNote
plain text: The extent and magnitude of coastal flooding is a function of the elevation inland flood waters penetrate, which is controlled by the topography of the coastal land exposed to flooding; storm surge conditions; and the broader bathymetry of the coastal area (Bell et al., 2017).
type: metrics

ExplanatoryNote
plain text: The figure below summarises common interactions between coastal flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
type: multiHazardContext

ExplanatoryNote
plain text: The governance structure of coastal zones may be strengthened in different ways (WMO, 2013): - Promoting better co-operation between different levels and sectors of government, taking into account trends of decentralisation and the need for (national) coordination. - Facilitating cooperation between the government and the private sector, taking into account trends of privatisation but also the need to safeguard the public interest. - Better involvement between stakeholders and citizens in development and management issues, to promote societal acceptance of development projects as well the long-term sustainability of development projects (arrangements and incentives for maintenance). - Creating arrangements for dealing with uncertainties and sharing of risks (insurance). There are many ways in which humans are trying to prevent the flooding of coastal environments. Technical measures for flood control include dike or seawall or levee construction (hard engineering structures) (Short and Masselink, 1999), maintenance of natural dune systems, protection of coastal ecosystems (natural defence) (Alongi, 2008) and different flood- proofing and accommodation activities. Engineered protection structures along the coast, such as sea walls, if not well planned, can alter the natural processes of the beach, often leading to erosion on adjacent stretches of the coast, which also increases the risk of flooding (Pope, 1997). Non-structural mechanisms also exist to mitigate coastal flooding: building regulations; coastal hazard zoning; urban development planning; spreading risk through insurance; and enhancing public awareness (Snoussi et al., 2008; Dawson et al., 2011). Generally, even moderate flooding hazards should be taken very seriously due to the potentially disastrous consequences, and flood protection is a key aspect in coastal disaster risk reduction. The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from traum…
type: riskManagement

ExplanatoryNote
plain text: The section above and the table below offer an overview of monitoring coastal flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management. | Which institution(s) produce(s) Disaster Risk Data/Information? | - Meteorological and hydrological services track storm surges, extreme weather events, and tidal patterns that contribute to coastal flooding. - Oceanographic and marine agencies monitoring sea level rise, wave action, and coastal erosion to assess flood risks. - National, subnational, and local disaster management agencies responsible for monitoring coastal flood risks, issuing warnings, and coordinating emergency response. - Geophysical agencies studying land subsidence, tectonic activity, and coastal geomorphology that influence flooding. - Health authorities assessing public health risks from saltwater contamination, disease outbreaks, and emergency response capabilities. - Engineers designing coastal defences such as seawalls, flood barriers, drainage systems, and resilient infrastructure. - Land use and urban planners integrating coastal flood risk assessments into zoning laws, building codes, and climate adaptation strategies. - Energy and utility companies monitoring risks to power plants, water treatment facilities, and communication networks in coastal areas. - Researchers and academics, including climate scientists, studying sea-level rise, storm surge impacts, and long-term flood mitigation strategies. - Organiszations and community representatives engaged in coastal resilience efforts, early warning dissemination, and flood preparedness initiatives. | How is the Hazard Observed/Monitored/Forecast? | Coastal flooding is monitored using tide gauges, satellite observations, and weather r…
type: monitoringEarlyWarning