Storm Surge

Unique identifier / Notation

MH0703

Synonyms

Not identified

A storm surge reflects the difference between the actual water level under the influence of a meteorological disturbance (storm tide) and the level which would have occurred in the absence of the meteorological disturbance (i.e., astronomical tide) (WMO, 2008, 2011, 2017).

Primary reference(s)

WMO, 2008. Technical Regulations, Volume III: Hydrology, WMO No. 49. World Meteorological Organization (WMO). Accessed 16 May 2025.

WMO, 2011. Guide to Storm Surge Forecasting, WMO No. 1076. World Meteorological Organization (WMO). Accessed 16 May 2025.

WMO, 2017. Regional Association IV – Hurricane Operational Plan for North America, Central America and the Caribbean, WMO-No. 1163. World Meteorological Organization (WMO). Accessed 16 May 2025.

Annotations

Additional scientific description

A storm surge is the rise in seawater level caused solely by a storm. It is the abnormal rise in seawater level during a storm, measured as the height of the water above the normal predicted astronomical tide. The surge is caused primarily by a storm’s winds pushing water onshore. The amplitude of the storm surge at any given location depends on the orientation of the coast- line with the storm track, the intensity, size, and speed of the storm, and the local bathymetry (NOAA, 2019a). This is illustrated in the graphic below (NOAA, 2019a).

A storm tide is the water level that results from the combination of the storm surge and the normal (astronomical) tide. A 3-metre (9.8 feet) storm surge on top of a high tide that is 2 metres (6.6 feet) above the mean sea level will produce a storm tide that is 5 metres (16.4 feet) above mean sea level. Storm surge should not be confused with storm tide. This rise in water level can cause extreme flooding in coastal areas, resulting from storm tides reaching up to 6 meters (20 feet) or more in some cases (NOAA, 2019b).

An illustration showing the difference in storm surges and storm tides — Storm surge vs. storm tide (NOAA, 2019.)

Metrics and numeric limits

Not available.

Key relevant UN convention / multilateral treaty

Sendai Framework for Disaster Risk Reduction 2015-2030.

Drivers

On top of a storm tide are pounding waves generated by the powerful winds.

Impacts

The area of seawater flooding may extend along the coast for over 100 km, with water pushing several kilometres inland if the land is low lying. The combined effects of the storm tide and surface waves can destroy buildings, wash away roads and run ships aground (Australian Government, 2020).

In 1953, for example, a storm in the North Sea resulted in a storm surge occurring simultaneously with a high spring tide. At the time, public warning systems were largely ineffective, and consequently many were underprepared. As a result, the associated flooding caused over 2500 deaths and caused substantial damage to homes, businesses, and farmlands. Following the 1953 storm surge event, the UK Government increased investments in sea defences and enhancing warning systems (Met Office, no date).

Multi-hazard context

The figure below summarises common interactions between storm surges 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.

Multi-hazard diagram

Risk Management

Examples of National Alerting Parameters include storm surge warning issued in Canada (Government of Canada, 2019) and an Advisory for storm surge watch/warning issued by the World Meteorological Organization (WMO, 2017).

An illustration showing the difference of storm surges to normal sea level conditions — Source: Matt McIntosh, NOAA

Monitoring

The section above and the table below offer an overview of monitoring storm surges. 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?

National, subnational, and local disaster management agencies responsible for monitoring storm surge risks, issuing alerts, and coordinating emergency response efforts.
Meteorological service tracking tropical cyclones, wind speeds, atmospheric pressure changes, and storm patterns that drive storm surges.
Hydrological service monitoring coastal water levels, river outflows, and tide interactions that influence storm surge intensity.
Oceanographic and marine research institutions studying wave dynamics, sea level rise, and ocean currents that contribute to storm surges.
Geophysical and geological research institutions analysing coastal landforms, subsidence, and sediment transport that affect storm surge behaviour.
Space and remote sensing agencies using satellite imagery, radar altimetry, and buoy data to detect and forecast storm surge development.
Maritime and naval safety authorities monitoring sea conditions and issuing advisories for shipping, ports, and offshore industries.
Energy and utility companies assessing risks to coastal power plants, oil refineries, and offshore wind farms from storm surge impacts.
Land use and urban planners integrating storm surge risk assessments into coastal zoning laws, infrastructure development, and disaster mitigation strategies.
Health authorities evaluating public health risks, including waterborne diseases, infrastructure failures, and emergency medical response needs.
Researchers and academics, including climate scientists and hydrodynamic modelers, studying storm surge forecasting, climate change impacts, and coastal resilience.
Environmental organizations and conservation groups advocating for wetland restoration, mangrove conservation, and nature-based storm surge mitigation strategies.
Coastal communities and local governments engaged in flood preparedness, early warning dissemination, and resilience-building initiatives.

How is the Hazard Observed/Monitored/Forecast?

Storm surges are monitored using tide gauges, satellite imagery, and ocean buoys to track rising sea levels and wave heights during storms. Meteorologists analyse wind speeds, atmospheric pressure, and storm intensity to predict surge behaviours. Computer models simulate how water will move inland, helping forecasters issue early warnings. These alerts help coastal communities, emergency responders, and infrastructure managers prepare for potential flooding and damage.