Tell me about tidal flooding?

July 15, 2008 6:44:42 AM PDT
article| David Murphy| Tidal flooding occurs along oceanfronts, back bays and other waterways like creeks and rivers that are directly linked to an ocean. Tidal flooding occurs when general ocean tides are combined with some other element to produce higher than normal sea levels. To understand tidal flooding, it helps to first understand what causes tides. To put it simply, it's the moon! All bodies in space (including moons, stars and planets) produce gravity. The strength of a body's gravitational pull is linked to its size and density. In the case of the earth's moon, its gravitational pull is strong enough to draw the oceans upward, toward space. The rise is slight, but enough to create higher ocean levels that we experience as high tides. As the water rises vertically toward the moon, it also spreads out horizontally (thanks to the earth's own gravitational pull), moving some of the water farther inland. But high tides, on their own, are not usually enough to cause more than the smallest bit of minor flooding. Usually, true tidal flooding requires a second element. The most common is an on-shore flow of air, usually produced by a coastal storm or an area of high pressure that is positioned in such a way that it sends a steady flow of air toward the beach. This inbound wind also moves extra surface water toward the shore. The combination of the extra water from the wind and the high tide can produce tidal flooding. Another element that helps cause tidal flooding is what's known as an astronomical high tide. When the moon passes directly overhead, it exerts a higher than normal level of gravitational pull, which can increase the normal tide level enough to cause flooding. An even better scenario is when both the moon and sun are aligned on the same plane as a given coastal location. In this case, the combined gravity of the moon and the sun exert a force that raises flood waters even higher. In both cases, the rise in sea level is often great enough to not only produce flooding near the coast, but also along adjacent bays, rivers and creeks that feed directly into the ocean.