Heading down the ICW, everyone pays close attention to the tides when navigating through the shallow spots but few pay attention to the effects of wind on the level of the water. Most everyone knows that an east wind will raise water and perhaps cause flooding and a west wind will push water out and make the shallow spots even more difficult. Who hasn’t looked at a posting on depth and then patted themselves on the back when they found deeper water (what a great navigator I am…) or been surprised when the opposite happened (the poster obviously was out to lunch…)
Have you ever wondered the basis for NOAA’s warnings on coastal flooding? Well, NOAA has particular buoys outfitted with water level monitors that give a reading of water height vs the predicted height from tide tables. If you know how to access the data, you too can benefit. For example, you may have 3 extra feet of depth in passing through the shallows south of Fernandina (or three feet less!) You have to know which buoys have the data you want and then how to access it, it’s not a one click operation. I’ve compiled a list of buoys reporting water heights that would be useful for negotiating the ICW but first an example. We were in Hampton, VA when Joaquin came through off shore and produced 25 to 35 kt east winds for two days which you would expect to push water levels higher than normal. We were on floating docks so we had some concern about just how high the surge would be so we watched a NOAA water level buoy site for that information. Here’s a typical plot:
The line of interest is the purple plot showing the delta between the predicted tide height (blue line) and the actual water height (red line). You can see that on 10/4/2015 the water was 3.5 ft higher than predicted by the tide tables!
This information is available all along the ICW from selected weather buoys and can be helpful when passing through areas where you really need to know the real depth accurately. That purple line above can be minus too in a strong west wind! One more example:
I have a 55.3 ft mast and I like to use the Cape May canal to reach Delaware Bay. I need to know the actual water height before going through since from past experience in normal weather the height boards read 58 ft at 0.0 predicted tide. In my fall of 2015 trip down, we had a strong east wind and the height board only read 56.5 ft at low tide! The low tide can actually be 3 ft higher than the tide tables! Now 56.5 ft is enough for my 55.3 ft mast but may not be enough for others. So here’s the list of stations I find useful with links:
Cape May Canal
You can click on “Show Data Listing” for the numbers in addition to the plots. I’ve noticed that when accessed on my iPad I get all three plots but when looked at on my laptop I only get the red and blue lines but I always use my iPad anyway. When planning your next passage, it never hurts to check on the predicted tide height vs actual, it only takes a minute and it could save you a lot of grief.
Robert Sherer (aka Bob423)
Author of “2015 ICW Cruising Guide” available on Amazon.com
You can follow our adventures down the ICW at fleetwing.blogspot.com