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The Intracoastal Waterway

Diving Deeper: Episode 56

historical nautical chart showing the intracoastal waterway

The Magenta Line

This NOAA nautical chart shows the Intracoastal Waterway. The magenta line is a directional guide on Intracoastal Waterway nautical charts.


HOST: Welcome to Diving Deeper. I’m your host, Kate Nielsen. Are you familiar with the Intracoastal Waterway? This route extends approximately 3,000 miles and is essentially two waterways along the Atlantic and Gulf coasts. While transiting this path, boaters will encounter different ports, U.S. Coast Guard facilities, military bases, and even coastal ecosystems.

Today we will be joined by Captain Shep Smith and Dawn Forsythe from NOAA’s Office of Coast Survey to share the history of this waterway and how it is noted on our nautical charts.

Thank you both for joining us today!



HOST: So, Captain Smith, can you expand more on my opening description of the Intracoastal Waterway?

CAPTAIN SHEP SMITH: The Intracoastal Waterway is a protected body of water that stretches all the way from New Jersey to Texas and meets many of the local coastal communities. It’s a protected waterway for small boats to be able to travel the coast of the East Coast and Gulf Coast of the U.S.

HOST: Can one of you tell us a little bit about the history of this route?

DAWN FORSYTHE: Well, it’s actually got a pretty interesting history. You know when motor boats started coming into their own, getting popular around the beginning of the 1900s, Coast Survey saw that there was a need for special charts for the recreational boaters -- for these power boats. And they started developing the Intracoastal Waterway route or the charts.

And so the first charts appeared around 1912. And they were basically put into a little book called the Inside Route, especially for recreational boaters and those charts were pretty static until the 1930s when the Public Works Administration, after the Depression a lot of money came into the government for recovery and infrastructure, and Coast Survey got some substantial funding and used it to put out field teams and did a complete rework of the Intracoastal Waterway. Those were around 1935 and the problem is that they’ve been pretty static up until modern times.

HOST: Is the Intracoastal Waterway intended more for commercial shipping or is it more that recreational boaters transit this waterway too?

CAPTAIN SHEP SMITH: Yes, it’s both and various different sections are used primarily by different groups. Some parts are clearly commercial in nature, where there’s tug boats that travel in these protected waterways. Other parts may have once been commercial and are now mostly recreational. But there’s a really very large community of thousands of boats that travel up and down the Intracoastal Waterway every season to go south for the winter and north for the summer, and they use the Intracoastal Waterway for most of the trip.

HOST: And how is the waterway depicted on NOAA’s nautical charts?

CAPTAIN SHEP SMITH: So, it is shown as a magenta line, which is how it’s commonly known, since it’s not actually named, the line itself has been called the magenta line. It generally follows the water courses of natural waterways and dredged channels and occasionally will show the way through a complicated maze of islands or small waterways.

HOST: And, is this magenta line, is it meant to be a navigation route that folks can follow directly?

CAPTAIN SHEP SMITH: Not directly. It shows the general route so it shows you which waterways comprise the Intracoastal Waterway. Now we make some attempt to ensure that the depiction of the line itself is in safe water in the water and not on the land, that sort of thing. But it’s not intended to replace all of the other ways that mariners choose a good route through these waterways.

DAWN FORSYTHE: One of the interesting things about the Intracoastal Waterway is that they’ll come up to a spot where different waterways will branch off and if you don’t have the Intracoastal Waterway chart you may end up where you don’t want to be. So that magenta line gives them sort of a directional guide on the branch of the waterway that they should take.

CAPTAIN SHEP SMITH: In addition, there are mile markers that are charted and those are often referred to by local businesses or marinas to say that we’re between mile 100 and 101 of the Intracoastal Waterway.

HOST: I’m guessing then that this magenta line appears on all NOAA nautical charts that are along the path in the Atlantic and the Gulf coasts? Is that correct?

CAPTAIN SHEP SMITH: It’s not quite true. There’s a series of charts that are really the ones that are intended to be used to follow the Intracoastal and the magenta line. There are intersecting charts that are really used for deep-draft traffic coming into major ports and the magenta line may happen to go over a portion of that chart, but it’s not necessarily shown on all charts and it’s not shown on the smaller scale charts, only on the larger scale charts of the coast.

DAWN FORSYTHE: The charts are called the Intracoastal Waterway charts and there’s, I believe, 53, 54 of those charts that show the magenta line, that specifically show the magenta line.

CAPTAIN SHEP SMITH: A few years ago, we started getting increasing number of reports of problems with the magenta line. Now, we have attributed this mostly to years of changes to the Intracoastal Waterway that weren’t necessarily reflected in changes to the magenta line. In addition, boaters are starting to use electronic navigation in these waterways to more precisely follow the line in a way that it was not originally intended. As a result, about a year ago, we suspended the publication of the magenta line while we went through a study of validating the requirement to keep it and to rebuild it so that it was fit for use. We’ve done that over the course of this last year and over the next few months we’ll begin to put it back on the charts that are published from here on out.

DAWN FORSYTHE: We should add that the response, especially from the recreational boating community, was tremendous in support of keeping the magenta line and recognizing it for the value that it can add to their boating experience.

HOST: Captain Smith, what is the future then for the magenta line?

CAPTAIN SHEP SMITH: We have begun a process of rebuilding it from the charts and from other source materials, from New Jersey all the way to Brownsville and as part of that, we’re encouraging input from experienced users, they can do that directly to us through our inquiry system on our website or they can use Active Captain, which we have recently signed a partnership with Active Captain to have access to their hazard database. So there are tools within that social network that we can use to get that information as well.

HOST: Since the chart updates will be rolling out over the next couple of years with the correctly placed magenta line, what is the best advice you have for boaters, during this interim period, for people who are using NOAA’s nautical charts and also want to route a course along the Intracoastal Waterway? What would you recommend for safe navigation?

CAPTAIN SHEP SMITH: They certainly should have the most up-to-date chart, whether or not it has an updated magenta line on it. In addition, pay close attention to the navigation aids, because they often change in between new editions of charts and they should always be respected, if their nav aid says to go on this side of the shoal, you should go on that side of the shoal. There’s a lot of information available through local knowledge and cruising communities and that sort of thing on how to handle some of the trickier inlets and passages and seek out and follow that advice as well.

HOST: On a personal note, in your personal lives when you all aren’t here at work, I wanted to ask if either of you ever done some boating and if you’ve traveled on the Intracoastal Waterway?

CAPTAIN SHEP SMITH: I have, I have not done a lot of it, but I have done the route from the Chesapeake down into North Carolina, following a section called the Dismal Swamp Canal which was actually surveyed by George Washington himself and dug I believe with slave labor back in the 18th century, but it formed a really important commercial waterway at the time connecting the Chesapeake Bay to the Albemarle Sound so I’ve traveled that section a few times.

HOST: And my last question for you both is just to see if you had any final, closing words to leave our listeners with?

DAWN FORSYTHE: First, I’d really like to thank the recreational boating community for responding so, vibrantly I guess is the word, to our request for what they thought about the magenta line, how they use it, and what they envision for the future. We’re making a lot of changes with our charts, with our chart production, with our chart delivery systems, with what we’ve got available for free on the web, and I think it’s really valuable for us to hear from as many people and as many different experiences and as many different uses for the charts and that helps us just produce a better product for everybody.

HOST: Thank you so much to Captain Shep Smith and Dawn Forsythe for joining us today on Diving Deeper to discuss the Intracoastal Waterway and the status of the magenta line on NOAA’s nautical charts. To learn more, please visit nauticalcharts.noaa.gov.

That’s all for today’s show. Diving Deeper will be back in just two weeks.

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