This is what can be expected when the following coastal flooding statements/watches/warnings are issued:
Splash over: The term says it all - waves will splash over seawalls, but nothing out of the ordinary is expected. It is a good idea to move vehicles away from seawalls and secure loose objects.
Minor Coastal Flooding: Nuisance flooding of streets adjacent to seawalls/rip rap. Some wave action going over seawalls. There have been some instances where minor coastal flooding is a little worse than might be expected. Storm shutters should be in place as a precaution.
Moderate Coastal Flooding: Much more of an impact than minor coastal flooding. Waves will be coming over the seawalls and roads will be flooded, making it difficult or impossible to drive across roadways. Waves will be substantial enough to hit houses along the oceanfront. Some beach erosion will take place as well. Storm shutters should be in place. People should consider leaving well before high tide.
Major Coastal Flooding: This is a serious threat to both life and property. Roads will be impassible. Houses that are not protected with shutter systems will receive damage-possibly serious to severe damage or even be destroyed. People should definitely consider leaving well before high tide, i.e. before the midpoint of the tide.
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The December 27, 2010 storm was a low end major coastal flooding example. Major Coastal Flooding can also mean flooding much worse than the December 27, 2010 storm. The National Weather Service also categorized the Halloween of 1991 and the Blizzard of 1978 in this type of flooding. If there is going to be a particularly serious flooding event they would also use descriptors such as Destructive, Severe, Life-Threatening etc.
Extreme Coastal Flooding: Presently there is no such category. However, the National Weather Service, Taunton is considering such a category for an event such as the Hurricane of 1938 for the South Coast of New England (areas such as Buzzard’s Bay). Tides during the Hurricane of 1938 exceeded 15 feet above normal in some places there.
Two important terms:
A Coastal Flood Watch is usually issued 24-36 hours before an anticipated event.
If the event becomes more certain to occur a Coastal Flood Warning is issued 12-24 hours before the event.