Floodtide

Floodtide is a term used in oceanography and coastal meteorology to describe an unusually high water level that results when an astronomical high tide coincides with additional water input from weather-related processes. The combination can produce tides higher than the typical tidal range, increasing the risk of coastal flooding in vulnerable areas.

Etymology and usage: Floodtide combines the ideas of rising water (flood) with the regular tidal cycle (tide). While not a formal technical term in every context, it is commonly used in maritime and coastal planning to describe peak water levels during periods of elevated tide plus extra water from weather systems.

Causes: The primary driver is the astronomical tide, but floodtides intensify when storm surge, wind setup, or low atmospheric pressure add water from the land or compress the water against coastlines. Spring tides, which amplify the baseline tide, can enhance floodtide effects, especially when paired with storms or heavy rainfall that drives higher river discharge near coastal interfaces.

Impacts and measurement: Floodtides can cause coastal flooding, beach and dune erosion, infrastructure damage, and saltwater intrusion into coastal ecosystems. Monitoring relies on tide gauges, weather radar, and numerical models that integrate tidal forecasts with storm tracks, sea-level rise, and local bathymetry to estimate peak water levels and issue warnings.

See also: Storm surge, high tide, spring tide, tidal bore, and coastal flood risk.