The U.S. Army Corps of Engineers is responsible for surveying, dredging, and maintaining federal channels in U.S. waters. Depths in these channels are of critical importance to deep draft commercial vessels.
NOAA nautical charts show federal channel depths in a number of ways. One of the methods is to create a channel tabulation, or a table of minimum depths, that will portray the latest survey depths. In general, channels 400 feet wide and greater will show minimum survey depths in 4 quarters. Channels 100 to 400 feet wide will show minimum depths on the left outside quarter, mid-channel for half project width, and right outside quarter. Channels less than 100 feet generally show depths based only on at least 80 percent of the project width; 40 percent on either side of the centerline.
Channel tabulations are sometimes created by the Corps of Engineers, and then passed to NOAA for application to the chart. Some Corps districts provide NOAA the channel surveys and NOAA cartographers create the corresponding tabulation. Since channel tabulation depths are of critical importance, the information is typically quickly provided to the mariner via USCG Local Notice to Mariners and NGA Notice to Mariners.