Great Loop: Intracoastal Waterway Navigation Guide

One of the most significant waterways for boaters making America's Great Loop voyage is the Intracoastal Waterway (ICW). Rather than being one continuous canal, it is a network of various water bodies such as rivers, bays, sounds, canals, etc. The mileage of the Intracoastal Waterway, according to NOAA, begins from Mile 0.0 in Norfolk, Virginia, and ends at Mile 1243.8 in Key West, Florida. The maintenance of the Atlantic Intracoastal Waterway from Norfolk to Miami lies under the Norfolk District of the U.S. Army Corps of Engineers.

What Is the Intracoastal Waterway?

ICW is not a single canal; rather, it consists of various canals. ICW miles have been used by the NOAA to mark location points in the ICW with Mile 0.0 in Norfolk and Mile 1243.8 at Key West. The design depth along sections of the federal project is different, but the dimensions of the federal project are not always real-time controlling depths. According to NOAA, the federal project is providing 12 feet from Norfolk to Fort Pierce, 10 feet from Fort Pierce to Miami, and 7 feet from Miami to Key West. But the Miami-Key West project has been done only till Cross Bank, and after that there remains a marked channel through the Florida Keys due to shoaling, tides, dredging, and other local factors.

Loopers find ICW very useful as boats do not need to go through open waters through the route of ICW. But just being called "protected" does not imply an absence of risks.

Understanding ICW Depths

An issue of importance when considering navigational factors is that of water depth. According to the current edition of Coast Pilot issued by the NOAA, there is a provision in the federal project for a least depth of 12 feet from Norfolk to Fort Pierce, 10 feet from Fort Pierce to Miami, and 7 feet from Miami to Key West. However, it must be noted that the federal project from Miami to Key West has been implemented up to Cross Bank at ICW Mile 1152.5 only, and further implementation of the federal project has been deferred for restudy. Thereafter, a marked channel runs from Cross Bank towards Big Pine Key.

The above figures provide information about federal project dimensions and not about the guaranteed real-time depths. Depths may have shoaled since the previous dredging operation, and therefore, boaters need to check their NOAA charts and USACE channel information.

ICW Navigation Aids and Charts

To follow the ICW, one must know about its navigation marks. Navigation marks include standard aids to navigation provided by the U.S. Coast Guard, along with the special marks for the Intracoastal Waterway. One needs to stay within the marked channel, while verifying his/her location through the help of up-to-date nautical charts.

The company GPS Nautical Charts offers comprehensive charts for the ICW with its i-Boating app. It includes the current nautical charts with features like depth shade, water level adjustment, GPS navigation, and even route assistance, taking into account the draft of your boat. The charts are also available for offline use.

Tides, Currents and Shoaling

The tides can have an impact on ICW navigation, especially in shallow areas. While a channel might have enough depth during high water levels, this will change as the water level drops due to the tide. Tidal currents could influence the boat's speed and control.

The issue of shoaling continues to persist. NOAA indicates that some areas of the ICW can be heavily shoaled up until the next maintenance dredging process. This is why it is important to note that a charted project depth should not be assumed for all parts of the route.

When planning for passage, compare the boat's draft against the available charted data, tidal predictions, and controlling depth information.

Bridges, Locks and Route Alternatives

Bridges make up a critical component of ICW navigation. Bridges are either fixed bridges or those which allow passage through an opening in order to accommodate boats. Loopers have to be aware of their vessels' maximum air draft and ensure compliance with bridge clearance and opening criteria.

The Norfolk to Albemarle Sound segment offers two significant route alternatives. The Dismal Swamp Canal and Albemarle and Chesapeake Canal offer alternative navigation routes between Chesapeake Bay and Albemarle Sound. Albemarle and Chesapeake Canal has Great Bridge Lock while Dismal Swamp route has its own locks and bridge clearances.

Currently, USACE publishes the operating conditions and navigation notice for these structures. As conditions may vary, boaters have to review the latest notice prior to selection and transit of either one of these routes.

Planning an ICW Passage

It is wise to prepare well before embarking from the dock for good ICW navigation. Rather than mapping out the whole route with one single chart or cruising guide, break up the body of water into segments and check the conditions within each segment.

Consider the latest updates on electronic charts, the draft and air draft of your boat, tides and currents, bridges, locks, weather conditions, and any notice from the Coast Guard or USACE regarding any change in the navigation of the waters.

The Great Loop navigational materials of GPS Nautical Charts would complement your efforts in checking these navigational issues through their route visualization tools and detailed charts. The i-Boating app of GPS Nautical Charts can also be used in your overall navigation plan.

Final ICW Navigation Tips

The Intracoastal Waterway would help in making the Great Loop less challenging through providing a safe coastal route, yet there is a need for navigation. Depths are not constant, channels may silt up, bridge clearance changes, and there are tides that impact on depth of water.

It is important to make use of the current navigation information and also the electronic chart. Check the conditions before every passage and not just the old information found in cruising guides. This is especially important for larger drafts and air drafts.

To Great Loop cruisers, the ICW should not be considered one consistent waterway but a navigation system that keeps changing all the time. The combination of NOAA charts and Coast Pilot information, United States Coast Guard navigation information, and US Army Corps of Engineers notices, among others, including the i-Boating charting software, gives a better base.

FAQs

1. What is the length of the Atlantic Intracoastal Waterway?

The NOAA's ICW mileage stretches from Mile 0 in Norfolk, Virginia to Mile 1243.8 in Key West, Florida. Statute miles are used to measure distances along the ICW.

2. What is the minimum depth for the Intracoastal Waterway?

Federal project dimensions provide for 12 feet depth from Norfolk to Fort Pierce, 10 feet from Fort Pierce to Miami and 7 feet towards Key West. These are project dimensions rather than guaranteed real-time depths.

3. Does Intracoastal Waterway navigation depend on tides?

Yes. Tides can alter water levels in shallow channels as well as impact the currents. It is important for boat owners to get the tide predictions and current data before any passage through the ICW.

4. Are there any alternative routes for the ICW?

Yes. There are alternative routes via Dismal Swamp Canal and Albemarle and Chesapeake Canal that run between Chesapeake Bay and Albemarle Sound. Both routes have their own locks, bridges and other characteristics.

5. Which navigational maps are best suited to the ICW?

The NOAA electronic nautical charts available now would be the base on which navigation planning should be done. GPS Nautical Charts i-Boating software is a suitable complement to the official maps.