The NJFloodMapper uses mean Higher High Water (MHHW) as a baseline for sea level. MHHW is the average of the higher high water height recorded each tidal day. Each month at the time of the new and full moon, especially strong tides (called spring tides) occur resulting in higher highs and lower low waters. A king tide is an especially high tide that occurs when the gravitational pull of the sun and moon reinforce one another. This extra-high tide happens twice a year at the times when the moon is closest to the earth. King tides can be 2-3 feet above normal MHHW and further exacerbate coastal flooding.
To learn more about king tides and see pictures go to http://bbp.ocean.edu/pages/357.asp.