Calculate Flood Return Period using Tide Gauge Data

Sea Defences, Humber Estuary, UK

GeoTide calculates the flood-return period as a function of sea-defence height using tide-gauge measurements

The combined effect of the astronomical tide and weather induced residual tide can result in tidal flooding. Atmospheric pressure and wind causes this residual tide, when large such fluctuations are known as tidal surges. Surges can be surprisingly frequent. For example, around the East coast of the UK, surges of one or even two meters occur many times per year. Being caused by weather, tidal surges cannot be tabulated in advance.


Surges can occur at any time, often they will occur during neap tides or spring low tides, in which case overtopping almost certainly will not occur. However, when surges occur near a spring high tide, overtopping of sea defences is much more likely.


The statistics of flooding is therefore the result of the combined effect of the statistics of the astronomical tide and the statistics of the residual tide, this is known as the joint probability method or JPM. Using this method, GeoTide provides statistical estimates of the flood-return probability and flood-frequency for a given height of sea-defence.


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