Source: adapted from National Geospatial-intelligence Agency (2005) World Port Index, Eighteenth Edition.

Harbor Types

There are eight major types of harbors:

• Coastal natural. Represents a sheltered site the outcome of a natural profile of the coast, creating a natural barrier such as a cape, a reef or an island. The above image depicts the harbor of Kingston, Jamaica. About 2,100 (46.0%) ports are in this category, underlining that the selection of a port site is dominantly influenced by the quality of the harbor.
• Coastal breakwater. An harbor lying behind an artificial breakwater construction, built from scratch or built to add to an existing natural shelter. It is particularly the case for harbors exposed to dominant winds, waves or the sea currents. Sherbourg, France is here depicted. About 810 ports (17.6%) are in this category.
• Coastal tide gates. An harbor behind a set of locks or other mechanical devices built to insure sufficient water levels in the harbor for all tide levels. In many cases ships can enter or exit the port only at certain times of the day when water levels are adequate. Only 39 (0.8%) such ports exist, such as Mumbai, India depicted above.
• River natural. An harbor located along a river where water is not retained in any artificial means. The harbor often consists of quays or wharves parallel to the river banks. Piers may also extend into the river. About 850 (18.5%) such ports exist, such as Jacksonville, Florida.
• River basins. A river harbor where basins have been excavated to accommodate ships, often parallel to the flow of the river. This confers the advantage of additional berth space without impeding fluvial navigation. 77 (1.6%) such ports exist, including Bremen, Germany.
• River tide gates. A river harbor behind a set of locks or other mechanical devices built to insure sufficient water levels in the harbor for all tide levels. Such harbors tend to be located close to the ocean, such as in a river delta or estuary for the case of Bremenhaven, Germany (estuary of the river Weser). Only 47 (1.0%) such ports exist.
• Canal or lake. A harbor located along an artificial canal or by a river accessible through a navigable waterway. 67 (1.4%) such ports exist, including Brugge, Belgium.
• Open roadstead. An harbor with no natural or artificial protection. They are often built to accommodate very large ships (such as oil tankers) or are in a setting where there are limited tides, implying that sheltering infrastructure are much less required (Persian Gulf, Red Sea, Gulf of Mexico). 580 (12.5%) ports are in this category, including Ra's at Tannurah, Saudi Arabia, a major oil port in the Persian Gulf.