Sunday, May 13, 2018

Hydrographic Surveys

There's no question that the internet has made sailing, cruising, and boating in general more safe. We have access to a plethora of weather and navigation information, all at easy access unless you happen to be offshore, accessible even then if you have enough money. The sheer volume of safety information is sometimes its demise, though, simply because there's just so much of it that it's hard to keep track of where you want to go for it and how much of it you want to use. One of the most valuable bits of information that a lot of cruisers neglect is the hydrographic survey. If you're traveling anywhere on the East Coast, using the inlets and then the ICW, the surveys are invaluable.

The hydrographic surveys are listed by district. The Wilmington District carries most of the surveys  for the Atlantic ICW, coastal inlets and crossings, harbors, side channels, and river projects. The Jacksonville District carries the Florida ICW and inlet surveys. Before transiting any of the areas it's a good idea to check the applicable survey. If you think you're going to be away from internet service, you can save the pdf files for viewing offline.

Here's a example of the hydrographic survey done for the Lockwoods Folly Inlet, done April 13, 2018. Most of the really notorious inlets are surveyed pretty frequently so the data is usually pretty accurate. It's pretty easy to see where you can go, and that you absolutely can't follow the magenta line in this case. The aids to navigation are moved frequently here and you can see that right now they go almost all the way to shore before they turn back to the channel. A few years ago, while transiting this inlet, we watched as a 40-foot sailboat run so hard aground here that he fell over on his side. He was single handing and was clearly following the magenta line on his autopilot. 



Hydrographic surveys can also be of use when determining the heights to bridges. Here's the survey for the Wilkerson Bridge in the Alligator-Pungo Canal. If you do use the survey for this purpose, just be careful to check the dates of the survey. This survey is from 2016 so it wouldn't be any use at all as a current estimation of water depth and bridge height.



Maybe the most beneficial use of the surveys is for determining what inlets to use when coming in from offshore. There are a lot of inlets along the coast that are extremely useful, but where the bottom changes so frequently that they require local knowledge. Surveys offer a wealth of that knowledge. Here is the Masonboro Inlet at Wrightsville Beach that we use frequently.




It's important to note that not all of the surveys look the same. Here's one from the Jacksonville District for the Saint Augustine Inlet on the Florida east coast. Note that the depths are printed right on the chart and are not color coded with a legend the way that the Wilmington District does it. It's also listed as eight pages in one file. Use the scroll bar on the side of the panel to see all the pages in this example.



It's also important to really pay attention to the details in the printed sidebar. On this example of the Naples to Gordon Pass survey, it says that it's a post Irma examination. Pretty useful for knowing how the storm changed things.




Unfortunately, the formats are not standardized. Each district has its own formatting and not all are as user-friendly. The New England District formatting is probably the most difficult to navigate. After going to the main linked page, you click on the navigation projects drop-down menu and then proceed to each individual state. Then they either offer a zipped pdf file for download, or you can click on each individual harbor or river for that survey.


Hydrographic Survey Districts:

There is a new site where all surveys will eventually be listed together, the main survey listing by state and inlet. It's fairly slow to load and respond to input, so be patient. You choose a state, then an inlet and then if there is a recent survey for that inlet it will be listed so you can click on it. If there is no recent survey it will tell you that. It's a good first effort at standardizing the surveys, but they have a long way to go.

Here are some of the more common districts.

The New England District

Wilmington District

Jacksonville District

Mobile District

Galveston District

San Francisco District

Seattle District (takes you to the main survey page)


There's a ton of information out there available to us as mariners. Navigating that information can be as difficult as navigating the waterways themselves.  I've found the surveys very helpful and if you use them and you have any additional pointers, please leave them in the comments.


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