Monday, April 26, 2010

Last week we reviewed a number of math words. Over the weekend I ran across another word that could have math implications - littoral.

The word first appeared in our newspaper because a new ship arrived in San Diego Bay, the USS Freedom. It's called an LCS (Littoral Combat Ship) and it's a 400-foot surface vessel intended for operation in the littoral zone (close to shore).  Here it is:

The USS Freedom can sweep for mines, chase drug runners, fight off pirates, and rescue sailors in distress. It can cruise for 3500 nautical miles without refueling and reach speeds of 47 knots (52 mph)! That's why the front deck is so clean - otherwise everything would blow off.

The very next day I read about a community in Brittany (Northwestern France). The author said that oysters are a normal source of protein for "French living on the littoral."

How does math fit into oysters and Navy ships? Well, how wide is the littoral zone? How close to shore? Who determines what's close? Is it how close a 400-foot ship can get to shore? Well, like many things, it turns out to be a very complex subject.

Littoral could be as simple as being from the point of highest tide to the point of the lowest tide (although on a flat beach, that can be miles). Or it could be much farther out, especially if you don't want to be grounding your new ship in the mud. Luckily the USS Freedom's draft is only 13 feet.

Here's a Navy drawing of the littoral zone. They consider it to be from the high tide region out to where the water is about 200 feet deep. It includes the beach, the back shore, the foreshore, the shoreline, the nearshore, the offshore and so on. Marine biologists generally consider the littoral zone to be much narrower.
Here's an oyster. It lives in the inter-tidal and sub-tidal zones (both within the littoral zone), and is not happy about being disturbed by these big Navy ships.

Here's a Google map of our region's littoral zone. There are many underwater features; some of them are shown here.