Source: adapted from National Geospatial-intelligence Agency, World Port Index.
The port site refers to its location concerning major maritime attributes such as the coastline and river systems. The harbor type refers to how a port is physically positioned. There are eight major types of harbors, and the above map depicts only large-sized ports:
- Open roadstead. A harbor with no natural or artificial protection. They are often built to accommodate very large ships (such as oil tankers) or in a setting with limited tides, implying that sheltering infrastructure is 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.
- 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. 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. A harbor lying behind an artificial breakwater construction, built from scratch or built to add to the existing natural shelter. This is particularly the case for harbors exposed to dominant winds, waves, or sea currents. About 810 ports (17.6%) are in this category.
- Coastal tide gates. A harbor behind a set of locks or other mechanical devices was built to ensure 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.
- River natural. A harbor located along a river where water is not retained by 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 or Montreal.
- 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.
- River tide gates. A river harbor behind a set of locks or other mechanical devices built to ensure 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, as in the case of Antwerp (Scheldt estuary) and Bremerhaven (Weser estuary). 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 Balboa in Panama and Brugge in Belgium.
Each of these sites requires different types of infrastructure to ensure proper port access and operation.