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Old 27-02-2016, 16:49   #1
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Water Depth Under Bridges

I am sailing a Catalina 18 in the relatively shallow waters of the Caloosahatchee River around Ft. Myers, Florida. There are a number of bridges in the area, and the NOAA charts seem to show that, generally, where these bridges are located, there is adequate water depth for my boat (which draws only about 2.5 feet). I am confident that I have ample water depth in the main channel under the central span of these bridges.

My question is this. Because the NOAA charts do not indicate any special water depth limits or obstructions under any portions of the bridges, can I assume that the water under the other spans of the bridges is what the NOAA chart is otherwise showing for that part of the river? Or do I need to be extra careful about using anything other than the main channel under a bridge, even though the chart does not show any special depth limitations under other parts of the bridge?


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Old 27-02-2016, 17:10   #2
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Re: Water Depth Under Bridges

I arrived in the same area a few days ago. Heading across the Okee after I fix my busted alternator.

I think, like you said, the charted depths near on each side of the bridge is a good indication of the depths through the side spans.

Also noticing where the local power boats use the side spans can help here. Even with thier draft, which often could be near yours, I feel they would prefer to have a comfortable depth under hull.

Lots of shallows in wide open waters around here. And the traffic is crazy on the weekends.

I did notice several local sailors using parts of the area outside of the causeway bridge to Sanibel that I wouldn't venture into when I arrived from offshore coming around from south of the island. So it's a matter of gaining local knowledge.

I've been accused of using the Braille method for acquiring this back in Alabama. :-) And I have redundant depth sounders.

Life begins at the waters edge.
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Old 06-03-2016, 08:37   #3
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Re: Water Depth Under Bridges

I did a lot of sailing in that area back in the late 70's, and ran aground a lot, even though my boat only drew 3.5'. I didn't have a depth sounder and didn't really pay a lot of attention to the paper charts (lesson learned) Stick to the main channels would be my advice.
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Old 06-03-2016, 09:30   #4
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Re: Water Depth Under Bridges

Stay in the main channel. Often times there is a controlled depth which means nothing less than the stated depth on the notations. Anywhere else and you chance it where you will have to go slower and keep a sharp eye on the sounder. You increase your chance of something bad happening when leaving the really should have local knowledge if you are going to do that.

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Old 06-03-2016, 10:13   #5

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Re: Water Depth Under Bridges

You can't assume any depth, at any point, is going to match the "charted" depth at a specific point. Nor can you be sure the charted depth is going to be accurate, even on the spot where it is marked. Your best bet is to stick in the main channel, try to confirm anything else from local knowledge, or else creep into other places carefully, with a depth sounder and lead line.

I was diving in a channel (leading under a bridge) that was charted at 40' depth. And I was down nearly 80 feet in that "40" foot channel. So much for charts.

Running aground, not so much fun. Running aground under a bridge...even less fun.
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