NOAA’s Ocean Today Holiday Season Special – THE FUTURE OF OCEAN FARMING video collection
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The First Shipwreck of 2023. Every boater’s nightmare.
Click here for 51’ Wasa Sailing Sloop Grounded Near Ocracoke Inlet Early On The Morning Of November 2nd
Click here for Frank Stick finds success, designs signature Banks cottage
CoastalReview.org
Fourth in a special series: Frank Stick’s Outer Banks development dreams.
Click here for A future tied to tourism: Stick presses for national park
CoastalReview.org
Click here for Today’s CoTabbastal Review: Scuttled Confederate ship had served both sides in Civil War
CoastalReview.org, by Kip Tabb
Click here for ‘Faith In the Future’: Troubles befall Virginia Dare Shores by Gilbert M Gaul
CoastalReview.org
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Click here for Boating Infrastructure Grants Can Make It Easy to Attract Visiting Boaters
Our thanks to Sean Welsh for this excellent, detailed explanation of bridge clearance boards.
Bridge Clearances Explained
by Sean Welsh USCG licensed Master inland, Mate near coastal
I was asked by the moderation team to write a few words about bridge clearance markings, after the comments
on a recent post revealed that there is a lot of confusion on the subject. That seemed straightforward, but, as it
turns out, it’s messy. That probably accounts for some of the confusion, so let me see if I can shed some light.
There is a standard for these markings, which are officially known as “Vertical Clearance Gauges” on the ICW
and other federal waterways, codified in federal law as 33 CFR § 118.160. Among other things, this standard
requires black markings on a white background, “foot marks” (horizontal lines of a specific size), specific spacing
of numbers, location at the right side of the channel, and regular maintenance.
If all bridges were marked according to this standard this would be an easy post to write. But the reality is that state or county road maintenance departments, railroads, and other bridge owners, and not the federal government, are actually responsible for installing markings on bridges, and there appears to be little consequence for these entities when they break federal law by straying from the standard. The bridge that prompted this post, the infamous Wilkerson Bridge in North Carolina, is one of the many non-compliant bridges and thus the source of much confusion.
Apart from the markings being a noncompliant white on a green background, the gauges on this bridge also lack
foot marks (horizontal lines) of any kind, and have numbers every foot. Since the numerals are 12" tall, this
means each number abuts the numbers above and below it. This is by no means the only bridge with this type of
marking, but it gets the most discussion here because the bridge is lower than ICW standards and is on a non-
tidal stretch of waterway, making it a tight fit for many sailboats.
On this type of clearance gauge, the clearance to low steel is between the largest number that is completely visible (not covered by any water at all) and the next larger number that is wholly or partially under water. This is a critical point to remember, because the human brain wants to see the largest number that is “mostly” visible, and count upwards from there. Among other things, this is because we are conditioned to see numbers increase from lower to higher elevations, and on a bridge gauge it’s the other way around.
This stands in contrast to many standards-compliant gauges, where the numerals are often (but not always) next to, rather than above, the foot marks. When you see a gauge where the foot marks fall mid-numeral, it is the bottom edge of the mark, and not the bottom edge of the numeral itself, that shows the level.
On the ICW, most compliant numerals will be either 12 or 18 inches tall and spaced every two feet. But on bridges sized for ships or large tows, which need to be visible from much further away, you will find gauges where
numerals may be spaced five or ten feet apart and are much larger in size. Compliant gauges, whether on fixed or movable bridges, show the clearance to “low steel” which is the lowest hard part of the bridge that is directly over the navigation channel. The edges of the channel are defined by the red channel limit lights, which are often on the fenders but sometimes hang below the span. If you stray outside these markers you may have lower clearance. Also, the “range lights” which are the green mid-channel lights that hang below the span, are not considered “low steel” and thus may hang down lower than the clearance measurement. If your clearance is close, pass between the range and the channel limits and do not take the range down the middle.
Having said that, once again there are some agencies out there installing non-compliant gauges and I have seen
some, notably on drawbridges, which show the clearance “at center” as noted on the sign. When in doubt, call
the bridge tender and ask. They are generally not allowed to tell you the clearance, but they can usually state
whether the gauge reads low steel or center-span, and in the case of low steel gauges, how much additional
clearance may be available center span.
While I am on the subject, now is a good time to remind everyone that bridge clearances marked on charts show
the low steel clearance at “mean high water” (MHW) for tidal bridges, and at “normal pool” for river bridges.
Actual clearance may be less; spring tides can be well above MHW and there may be freshet on top of that, and
river pools vary greatly.
Bridges, their clearances, and movable bridge regulations and schedules can be found in the relevant edition of
the Coast Pilot. Every skipper should carry the local Coast Pilot edition on board, available as a free download.
Temporary clearance changes, for example due to construction work, can be found in the current issue of the
Local Notices to Mariners (LNMs), which, again, every skipper should download and check as part of their
voyage planning.
BoatUS is the leading advocate for boating safety in the US and A CRUISERS NET SPONSOR!
Click here for A 27-Inch Chartplotter? | Prop Inspection Guide | Alternative Fuel Test Results | 5 Hot Fall Fish
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The total number of Atlantic tropical cyclones that strengthened from weak Category 1 storms into major hurricanes within a 36-hour window has more than doubled in the last 50 years, a new analysis finds.
Click here for Pace of cyclone strengthening has doubled since 1971
CoastalReview.org
We at NAVCEN are thrilled to announce significant advancements in our ability to deliver Broadcast Notice to Mariners (BNMs) across all US waterways. This achievement is the culmination of years of effort, and we’re proud to relay that every single one of the USCG’s 37 Sectors and 9 Districts are now actively transmitting BNMs. As part of our commitment to harnessing technology for safer navigation, we have augmented the required VHF radio delivery method to providing real-time information directly to registered devices. This ensures that mariners and the public can access real-time safety data wherever they are, at the touch of a button. For those involved in route planning, we’ve also introduced an archive on the NAVCEN website containing all BNM data, making it even easier to check the status of navigable waterways before setting sail. NAVCEN is dedicated to leveraging technology to bolster the safety and efficiency of our maritime community, and we invite you to explore these enhancements by visiting the Broadcast Notice to Mariners section on the Navigation Center website: Broadcast Notice to Mariners | Navigation Center (https://www.navcen.uscg.gov/) |
Click here for The USS North Carolina’s Next Battle
Second in our series: Frank Stick was looking to land more than a few bluefish when he visited the Outer Banks in the 1920s, the illustrator and sportsman saw opportunity here.
Click here for ‘Millions Have Been Made’: Frank Stick changes careers
CoastalReview.org
New series: Two-time Pulitzer Prize winner Gil Gaul dives into newspaper clippings, archives and other sources to reveal the complex story of the New Jersey artist, outdoorsman, developer and speculator who filled miles of Outer Banks beaches with vacation houses.
Click here for Uncovering the improbable tale of multifaceted Frank Stick
CoastalReview.org
Click here A special time to remember the 1896 E.S. Newman rescue by Joan Collins
CoastalReview.org
Click here for Join Ocean Today for a Journey into the Deep Sea and into our Past
Drawing from maps created by a teacher and his students, historian David Cecelski aims to get a feel for the lumber mill villages in Hyde County that have long since disappeared.
Click here for Wharf pilings and sawdust: Visiting Hyde’s lost villages by David Cecelski
CoastalReview.org
A longtime CRUISERS NET SPONSOR, historic Edenton always has an exciting calendar of events and places to visit! Edenton is at the mouth of the Chowan River on the northwest shore of Albemarle Sound.
Click here for Edenton’s history ‘an everyday part of life’ for its residents by Eric Medlin
CoastalReiew.org
Click Here To Open A Chart View Window Zoomed To the Location of Edenton Harbor City Docks
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