"Changing Sea Levels - effects of tides, weather and climate"

Flood Warnings

Warnings of imminent coastal flooding are issued by operational agencies. In many cases these are meteorological authorities, which makes sense as coastal flooding is normally asociated with extreme weather conditions, and because they are operating and can respond at all times.

Warnings fall into three categories.

Tropical storms associated with cyclones are found in many places. Many authorities have useful web sites, including Australia, Hong Kong, India, and the USA. Low-lying islands of which there are many in the Pacific Ocean, are especially vulnerable.

For extra-tropical storms, there are good sites for the North Sea. The UK Met Office issue warnings; these are especially important for deciding when to operate the Thames barrier that protects London. NOAA offers valuable information and details of warnings for the USA.

Tsunami warnings have a very different genesis. As discussed in Section 6.7, first an earthquake of significant amplitude must be detected, then a coastal tide gauge must detect an actual wave. In theory a single centre could do this globally, if information is centrally available. Extra centres can add necessary backup coverage. In practice many regions feel the need for more immediate involvement and more local systems. At present the two main centres are in Hawaii, and Japan. The Hawaii Center serves as the International System for the Pacific, and now more generally. Following the December 2004 tsunami the Intergovernmental Oceanographic Commission of UNESCO has been working with its Member States to develop a long-term system. This has included making assessments of the needs of all the countries affected by that disaster.