Tides

Wednesday, 11-18-2015. 0830 Winds light NE Temp 60 degrees F.

Anchored on a low stand ebb tide in Church Creek with five other boats.

Everybody gets the basic idea about tides I suspect.  Tides are the daily rise and fall of sea level and are the result of interplay between the gravitational forces of the Earth, Moon and Sun and the rotation of the Earth. That interplay results in a ‘bulge’ of water that moves around the planet to create the tides. Where these celestial bodies are in relation to one another at any given moment in the yearly and monthly cycle determines the tides in a given location. Local geography generally determines tide height and current velocity.

An ebb tide (falling tide) is occurring when water is moving away from a land body towards the ocean. A low stand tide (low tide) is when the lowest water height is reached at a particular location. Ebb flow does not necessarily stop at low tide.

In a future blog entry, on which I’m sure you just can’t wait, I’m ‘gonna splain’ in great detail just how complicated tidal flow is and why its consideration is important for safe navigation.

Here is a little teaser.

In Virginia on the Chesapeake Bay the average tidal range is on the order of a few feet. On the same day, where we are now on Church Creek, in South Carolina, the Palmetto State (I’ll get to that later), the tide range is on the order of six feet. Just south of here in the Beaufort area its eight feet. Quite a difference. Why is that? To make a very long story very short, it has to do with geography. The bay is large and its inlet from the ocean is broad compared to Port Royal Sound and its relatively narrow inlet, which feeds the Beaufort River, where we are now. The same very big bulge of Atlantic Ocean water is hitting both those locations, but the Bay simply has more room, more volume, in which to fit the incoming water. Currents at the broad Bay entrance are modest for the same reason. At the narrow Port Royal Sound Inlet the incoming current is stronger, because water flows faster through a smaller pipe.

From Church Creek we crossed the North Edisto River, the Dawho River, the South Edisto River, passed through Fenwick Cut to the Ashepoo River then through the Ashepoo G Coosaw Cutoff to the Coosaw River into Brickyard Creek and finally into the Beaufort River, where we rounded the peninsula, passed through the Ladys Island Bridge and came to rest on anchor in the Beaufort Harbor at 1400.

Along the way, it starts to rain.

More boring geography stuff? Partially to illustrate another point (besides tide considerations), that being that South Carolina has a remarkably large and complex array of coastal rivers meandering here and there through ecologically productive, tidal saltwater wetlands, brimming with wildlife; birds, fish, shellfish, marine mammals, crabs, worms and insects (yes those too) and a fascinating assortment of wetland plants. In fact South Carolina has more salt water wetland acreage than any Atlantic Coastal state. These areas are a national treasure in my view. It’s fortunate that average tides are so high here. High tides in low coastal areas make for extensive salt water marches that must be infinitely harder to develop.

Good news.

So there.

Tomorrow we hope to tie up in the Beaufort City Marina where we are going to hunker down for a couple of days.

Good night.