Minimum Channel Depth Standard?

[Elzaar]

This seems like a silly question I should know the answer to, but as a PNW sailor looking at charts around Florida, I confess it has just never come up and if I once knew the answer I have long forgotten it.

I'm looking at OpenCPN charts on my laptop to check depths on the Gulf side of Florida. The noted depths tend to be borderline for my draft *outside* the marked channels, but I can't locate the depth *within* any of the marked channels on the charts.

This raises two questions really -

1. Am I missing something looking at these charts in OpenCPN that I should be catching as a Note someplace?

2. Is there a standard minimum depth implied by a marked - obviously dredged - channel?

I usually would drag out a paper chart if I were aboard and may even find an answer there, but I'm locked in a hotel room for another few days honoring Canada's Covid Q rules. I got nowhere with Google.

Thanks!

[requiem]

Do you have an example location? I quickly zoomed in to the Crystal River and see this note on both the RNC and ENC products (note that for the ENC it's in the chart metadata).

CRYSTAL RIVER

The controlling depth was 1.5 meters/5 feet on the centerline
from Light 1 to daybeacon 21 (28°55'35N, 82°41'38"W); thence
1.5 meters/5 feet to daybeacon 23, opposite Bagley Cove; thence
0.9 meters/3 feet to the public boat ramp.

About 4-5 years back NOAA announced they would replace controlling depths on RNC/paper charts with the original project depth, so more recently updated raster charts may lack this information.

[Elzaar]

Thanks for the response.

I actually am looking at Crystal River and also the dredged channels to the north of Drum Island (north of Crystal River). Crystal River shows the depths, but not clear if those relate to the channel markers or are just the general river depths. The dredged channels north of that I show depths outside the grey channel, but no depths within it.

My settings for "Show ENC Soundings" is toggled on, but I don't have any RNC options showing. Even with the toggle on I don't get any data for the dredged channel itself.

Where do I find the Chart Metadata?

Thanks again.

[requiem]

North of Drum I see the Withlacoochee River and the Cross Florida Greenway.

On the RNC you should see notes for each of them on the land area of the chart; one lists controlling depths from 2013, the other gives a phone number. Between marks 19 and 21 of the Greenway you should see the project depth listed: do not trust it; that's what the phone number is for. There are no additional data with an RNC; what you see is all you get. (I suppose metadata wasn't the right term; it's simply additional chart data.)

On the ENC you can right-click an area and select "Object Query..."; do so for the Withlacoochee, scroll down until you find the "dredged area" section, and match it against the note on the raster chart.

Do the same for the Greenway and the branch of the channel leading to the power plant south of the Greenway and notice how one lists the project depth and the other a controlling/maintained depth.

[BillKny]

Originally Posted by Elzaar

Thanks for the response.

I actually am looking at Crystal River and also the dredged channels to the north of Drum Island (north of Crystal River). Crystal River shows the depths, but not clear if those relate to the channel markers or are just the general river depths. The dredged channels north of that I show depths outside the grey channel, but no depths within it.

My settings for "Show ENC Soundings" is toggled on, but I don't have any RNC options showing. Even with the toggle on I don't get any data for the dredged channel itself.

Where do I find the Chart Metadata?

Thanks again.

You are looking for something that doesn't exist. Soundings are not published for dredged channels. Depthsin these locations change all the time, and vary depending on the local environment and how long since the last dredge.

You have to look at the project data, and go with that and whatever local information you can "dredge" up.

[hpeer]

Try AquaMap in an iPhone with the upgrade. Then you have access to soundings over the last 3 years. It seems most areas of concern have been charted.

I dont see any recent soundings for Crystal River. Here is a bit of Wichlacotche whatever.

[Elzaar]

Thanks so much for the replies and the step-by-step instructions. I have only set up OpenCPN as a back-up, so this is great practice and information. I was unaware of the "Object Query" function, and have only downloaded ENC Charts. Now wondering if I should download RNC charts for areas I actually expect to cruise. I carry paper charts for every place I sail now.

When I pull up the "Dredged Area" text box it shows "Area 19.7 ft. Maintained depth (10)" Am I correct in assuming it is stating the theoretical maintained depth is 10 feet or is that referring to some note somewhere?

Thanks for the iPhone upgrade idea, but I have android and Windows based stuff. Hopefully something like AquaMap will become available for non-iOS soon.

[hpeer]

Ios AND android

Aqua Map - App Master functions

[requiem]

I suspect Aquamap is integrating that additional data from here: https://navigation.usace.army.mil/Survey/Hydro

They only seem to provide data in ENC form for the Mississippi River System, but you can get a PDF showing the soundings. The one for the Crystal River was last done in 2013, and once you look at it you'll see why you might want to navigate with particular care.

Regarding the "maintained depth (10)", ten is the attribute value for "maintained depth": Attributes S-57(3.1) QUASOU (mouse over for definitions, etc.)

19.7 feet (well, 6 m) is thus "the depth at which the channel is kept by human influence, usually by dredging".

As for paper and RNC, in areas where charts are updated more often you'll eventually run into more cases like in the image below (taken from Tampa Bay entrance). Of course, over the next few years the raster products are being retired, so either way the future is ENC.

[Pandor]

Originally Posted by Elzaar

Thanks so much for the replies and the step-by-step instructions. I have only set up OpenCPN as a back-up, so this is great practice and information. I was unaware of the "Object Query" function, and have only downloaded ENC Charts. Now wondering if I should download RNC charts for areas I actually expect to cruise. I carry paper charts for every place I sail now.

When I pull up the "Dredged Area" text box it shows "Area 19.7 ft. Maintained depth (10)" Am I correct in assuming it is stating the theoretical maintained depth is 10 feet or is that referring to some note somewhere?

Thanks for the iPhone upgrade idea, but I have android and Windows based stuff. Hopefully something like AquaMap will become available for non-iOS soon.

I’ve always liked having both the RNC and ENC charts available to compare.

But in 2019, NOAA announced a change to the way they would present the depths on RNCs. They will be eliminating controlling depths and supposedly will only be reporting the project depths in the future. As we all know, with the minimal dredging that USACE has been funded to complete, project depths aren’t that useful. So in the future, ENCs are probably your best bet for an accurate dredged channel depth.

From NOAA:
NOAA announces change in channel depths on raster nautical chart products
NOAA’s Office of Coast Survey recently announced plans to change the U.S. Army Corps of Engineers (USACE) maintained channel depth values on raster nautical chart products, which include paper nautical charts and the corresponding digital raster navigational charts (NOAA RNC®). Minimum depths (also called controlling depths) are collected during periodic USACE sonar surveys of channels. In the past, these depths were provided on raster charts, but controlling depths will now be replaced with the original channel design dredging depths used by the USACE (called project depths). Standardizing depth presentation on these products will improve data consistency and overall safety. Implementation begins in early 2019.

NOAA’s suite of electronic navigational charts (NOAA ENC®) are not affected by these changes. Mariners are encouraged to use NOAA ENCs for critical safety information as these products are typically updated up to one month ahead of raster products.

Why the change?

The USACE makes the depth information from recent surveys publicly available on their website before NOAA nautical products are updated and published. NOAA prioritizes making updates to ENC over RNC products. This often results in RNC products not accurately reflecting the most current controlling depth values (as represented on NOAA ENC and the USACE website). To eliminate inconsistencies among controlling depths, NOAA will only show project depths on raster chart products in the future. The Initial implementation of this change will focus on deep draft shipping channels where the primary product used for navigation is the ENC.

[Elzaar]

[QUOTE=requiem;3436975]I suspect Aquamap is integrating that additional data from here: https://navigation.usace.army.mil/Survey/Hydro


Excellent information, and thanks again for the responses. I'm glad I asked about the basic depth question - This link alone is seriously cool. Definitely going to need to spring for the forward looking sonar if the boat is going to move to Florida.

[Shanachie]

As a general rule, a 4.5-foot draft will get you into the vast majority of places. At 5 feet, you have to be a little careful about tides, but it's still OK.


More than 5 feet, you're going to have problems.


The difficulty is that sand is always shifting because the vast majority of coastal communities are built on sandbars that are always changing shape. The state also restores beaches that then erode and fill up channels.



I've seen 5 feet in lumps on the Gulf ICW that were supposed to be much deeper. Some channels only have temporary markers because they have to be shifted so much due to shifting.



So the charts often don't reflect reality.



On the somewhat bright side, you occasionally find unmarked deep channels that came about because developers in the '70s and '80s would steal fill from bay bottoms to build up the islands they had communities on.


In the south end of Boca Ciega Bay, for example, where the chart says five feet, there is a 25-foot-deep channel left there by a developer who needed dirt for nearby condos.


The downside is that the bay was once a wonderful fishing spot. After the developers ruined it, not much fishing goes on.



Those of us who sail western Florida know that it's one of the world's great cruising spots. But we also carry tow insurance because we know that, sooner or later, we will run aground.

[Elzaar]

Good information, Shanachie. When we were visiting there last Winter we watched a storm blowing one boat after another toward shore from at least 500 yards out and then miraculously stop - usually still at least 100 yards out. Then a local explained that we were looking at boats anchored in no more than eight feet of water that were then "grounding" in five feet. It was educational.

My boat claims to draw only 4'10", but I'm sure its more than 5' or more when actually loaded up. I know from experience she can handle groundings, unfortunately.

Since you are local, I've been checking out areas from Punta Gorda to as far north as Tallahassee. I gather both Charlotte Harbor and Tampa have good sailing and good sailing groups. Any areas you would steer toward or away from? Is moorage difficult to come by? If I relocate, the boat will likely stay in the PNW for another season or two, but some time soon I'd be relocating it to somewhere in Florida.

[Shanachie]

Tarpon Springs on south is all good sailing. I sail on Tampa Bay; It's wonderful for day sails and has many good anchorages a day sail away.



With five feet, you can make it all the way down western Florida and through the Keys, watching for tides in places such as Spanish Channel and Islamorada.



It's 600 miles or so round trip from St. Pete to Key West, counting ducking into anchorages for the night. A great trip. You can spend six weeks or so checking everything out.


March through May is the best time for long trips. Earlier and you have to deal with weekly northers. Later and you have hot, humid weather with thunderstorms.


If you are hardy, you can extend your cruising time. Day sails are 12 months a year.



North of Tarpon Springs, there are fewer places to go and much shallow water. You have to travel far in between anchorages.

[Auklet]

We lived in St. Petersburg in the 1990s and extensively sailed the SW coast of FL between Dunedin and Ft Myers including much of Tampa Bay, upper and lower, in a yacht of 5’ draft. The marked channels, including much of the ICW, were typically at least 10 ft but there were places as shallow as 5-6 ft. Sailboats with 4 1/2’ drafts or less could go most anywhere marked and beyond w/o issues, as noted above. I can’t answer your question regarding controlling depths on e-charts of the area, but the paper NOAA charts we used contained what information we needed, most of the time. Certain channels in SW FL must be dredged, such as Big Sarasota Pass and New Pass. In cases when dredging has not occurred as scheduled the passable water might not lie between the channel markers, etc. The charts did not show this. If planning to use those channel passes you might be best served by checking with the CG or other local sources when planning your trip, or the latest version of Coast Pilot for the eastern Gulf. At least a few yachts were fetched onto the shoals at Big Sarasota Pass in the 1990’s trying to enter Sarasota Bay from sea.

Regarding the remark above about grounding. We went aground or touched bottom many times, usually not seriously. We could get off using the “normal” techniques, but were twice I remember pulled or pushed off by passing power boats. Not the greatest of situations. However, inside the barrier islands grounding is mostly just an inconvenience. Going aground entering from sea or along the Gulf coast is potentially much more “dangerous” for boat and crew. So, mind your depths carefully when traveling close along the Gulf coast. For some hair-raising fiction about sailing the Gulf coast of Florida, read the first three books of Robert N. Macomber’s “Honor Series.” It’s set during the Civil War, where the Union is maintaining a blockade of Gulf ports from Cedar Key to the eastern Florida Keys. Good read.