Nautical maps--Am I reading it right? (Soundings)

This is probably going to be one of the easiest GQs ever answered in the history of the Dope. But then again, I could be wrong. . .

I came across a particular site, and saw a map of Charleston, SC Harbor. Am I reading the “soundings” correctly, in that the water in and around Fort Sumter is only really a foot or two deep (at high tide)? In some spots, I could literally wade across sections of the harbor?

It seems deceptively easy, so I thought I’d ask. . .

Yeah, not that I’d want to wade across the bay. :eek:

At the lower right it says “Soundings in feet at mean lower low water.” So you’re seeing depths at low tide (technically, the average of the lower of the two daily tides), not high tide.


. . .low tide, that’s what I meant to say.

Wow. I would have thought the bay would be fifty feet deep or so. . . I guess it really is that easy to read.

Hrm. Interesting.

They are easy to read. But in order to get to most of that 1-2 feet of water you’ll be waiding through some nice marsh. I also saw some "M"s, which I think means muddy, but it’s been a few years since I worked at NOAA so I don’t remember for sure. You also need to know that those are sounding curves and not contours. Curves are not exact so it’s possible to have some deeper parts where you’re walking. Have fun storming the castle.

P.S. Most people (and all sailors) would call that a chart, not a map.

Tide is a surprising thing. It takes quite a bit of time to wrap your head around the fact that water levels can change not just a bit, but by 8 or 10 feet over the course of eight or so hours. There’s an area around here called Joppa flats where boats regularly fish – it’s maybe a mile across. At low tide, you can barely navigate it with a kayak (which has a draft of six inches or so) and you probably could walk across it.

And as I’ve found out to my sorrow, broad areas of tidal river that look perfectly navigable can become wide, dry sandbars at low tide upon which your boat will rest until the next high tide.

This is why I’m in the Air Force and not the Navy. :smiley:

Not that we have ‘charts’ neither . . . :smack:

And the rest. The Bay of Fundy it’s more like 45 feet. Parts of Western Australia get 30 feet or so.