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Source: National Transportation Atlas Database & National Geospatial Intelligence Agency.

The American Waterway System and Channel Depth at Major Container Ports

Port locations and sites are preliminary constrained by the quality of maritime access they can provide. A core component of this access is related to the depth of the waterway system and of port access channels in particular. The above maps illustrates the main "internal" navigation channels linking the United States, including Hawaii, Puerto Rico and the Panama Canal routes as well as the channel depth of the major container ports.

The North American continent, unlike its European counterpart, is not very prone to inland waterway distribution and is composed of three major subsystems:

• The Eastern Seaboard, with the exception of the St. Lawrence / Great Lakes system, offers no significant navigable river system as the Appalachian Mountains are just a few hundred kilometers from the coast. The upper Great Lakes (Erie, Huron, Michigan and Superior) offer good navigation depths, but navigation is limited by the waterways between the lakes and by ice in winter. Further, access to the Atlantic is limited to the depth and lock size of the St. Lawrence Seaway, which is closed for a few months during the winter. The St. Lawrence enables to go deep inland, but maritime vessels can go up to Montreal, which is essentially at the same longitude than New York. There are channel depth limitations for accessing several East Coast ports that has induced dredging projects such as in New York (up to 50 feet). The Eastern Seaboard however has also a complex but underused coastal transport system. The Intracoastal Waterway services most of the Eastern Seaboard and consists of a series of bays, inlets, sounds and artificial canals.
• For the Gulf of Mexico, the Mississippi inland waterway system is extensive but limited to depths of less than 15 feet for the most part. Under such circumstances, ports along the Mississippi are dominantly handling barges loaded with agricultural commodities, which implies a highly seasonal traffic. Additionally, the Mississippi system has a north-south orientation while most of the goods flows are east-west, implying a limited potential to service intermodal freight movements. Like the Eastern Seaboard, there is an Intracoastal Waterway ranging from Texas to Florida.
• The Western Seaboard has four major deep water gateways, Seattle, Portland, San Francisco and Los Angeles but poor waterway access to the interior because of the Sierra Nevada and Rockies. The only exception is the Columbia River basin which is accessible to deep-sea ships up to Portland which is about 160 km inland.

As the world container fleet gets upgraded with larger ships, major ports are facing the challenge of accommodating deeper vessel drafts. While a typical Panamax containership could be accommodated by a 35-foot channel, the new generation of post-Panamax containerships handling between 4,000 and 8,000 TEUS requires a channel depth between 42 and 52 feet. Under such circumstances, many ports are not accessible to the largest containerships. This has triggered a "race to the bottom" for ports at the depth margin, such as Charleston, New York and Savannah, all of which have completed a phase of deepening above 45 feet. By 2009, access to the major container terminal facilities of the port of New York were deepened to 50 feet. Yet, such projects are very expensive and require careful consideration of the marginal benefits they convey.