May 18, 2011
Channel Key Pass (ICW through Channel Key Banks) – Navigational Conundrum Resolved
N 24 48.768 W 80 54.708 (Green #5 & #7 and Red #8)
by Charmaine Smith Ladd
The navigational conundrum posed in my article of May 11th has been resolved. Love when that happens! LOL
To quickly refresh your memory, see the illustration below. This is in the waters of Florida Bay, which average 7-9 feet. While traversing the Bay between Channel Five and the Seven Mile Bridge, we aboard September Sea came across what seemed to be an unusual navigational aid configuration along the ICW at Channel Key Pass:
Channel Key Pass (ICW through Channel Key Banks) N 24 48.768 W 80 54.708 (Green markers #5 & #7 and Red marker #8)
It seemed as per the chart, going outside Red marker #8 would keep my 5’8 draft in consistently deeper water and away from the shoals. I wondered why the marked channel was so narrow, seemed to come so very close to the southern shoal of Channel Key Bank, and was in a slight “S” configuration. That’s a lot more to think about than merely opting to go outside Red Marker #8 and be in what the chart shows as 7 ft. waters. Then I thought about the possibility of navigating this area at night or in foul weather! I had to know more about this area before either of those scenarios ever became a reality. Therefore, being daytime, I decided to follow the marked channel. With good daylight it was easier to see the shoals. Yet still, when passing through the marked channel, my keel was in only inches of water. That’s when I began to doubt whether I had made the correct decision.
Since that time, I have researched to view satellite images of the area (seen side-by-side below). The images show distinctly lighter colored areas outside Red marker #8. This is an obvious indication of inconsistent depths. The black and white image on the left reflects a yellow ring I have drawn around the questionable depth area. The Google Earth image on the right, being in color, does not show that contrast as clearly. The yellow pins I’ve drawn flank the northern and southern boundaries of Channel Key Pass per NOAA charts. It is apparent the yellow ringed area lies within those boundaries.
Satellite Image Comparisons of Channel Key Pass
In the future, I will take the marked channel through Channel Key Banks. It is my belief that while navigating the “S” curve, I allowed the stern to swing a bit off the centerline. This would explain why my depth sounder went off and showed only inches of water. I was a bit too close to the shoal of Green Marker #7. When navigating this Pass, be sure to stay in the center of the passage. It is quite narrow and confusing, but it is totally accurate. The chart does show that a bit of shoal overlaps the Pass. Stay a bit more north when passing Green Marker #7 and you’ll be just fine.
Most boats in Florida Bay do not have the worries about depth as we who draw 5’8 or more. The other sailboat observed that day which decided to pass to the North of the marked Channel (outside of Red Marker #8) was more than likely as confused as we were. His choice was probably decided as per the chart showing enough depth within that course. His thinking was to not risk any dealings to the shoal off Green Marker #7. But now that I have seen the satellite images, it is clear that is not the safest course to take. The satellite images also reveal the logic behind the configuration of the Channel Key Pass markers.
My next trip there will include going out in the dinghy and taking some depth soundings of the yellow ringed area with a handheld sonar. Even though the satellite images indicate some shoaling there (enough at this point to avoid the area with my 5’8 draft); this writer’s curious nature would love to know what truly lies beneath!
The NOAA satellite image used here was obtained from a fellow cruiser who has a program on his chartplotter which allows him to overlay such images. Google Earth images were easily obtained by downloading the resources directly from Google Earth. However, the side-by-side comparison shows that the contrast images on Google Earth are not always clear enough to be used for detecting navigational hazards at sea. It is evident that in this case, the NOAA satellite image most clearly reveals the answer to what once was the Channel Key Pass navigational conundrum.
Cruisers helping Cruisers = Conundrum Resolved!
Charmaine Smith Ladd
SSECN Special Correspondent, Florida Keys
“Bringing you the low down from down low!”