Source: adapted from National Geospatial-intelligence Agency (2005) World Port Index, Eighteenth Edition.
Number of Large and Medium Ports by Channel Depth
The distribution of the number of large ports by channel depth follows a normal distribution, with an additional spike of ports having channel depths of more than 75 feet. This is explained that sites with deep draft are preferred. The number of large ports that can accommodate a post-Panamax containership is limited, since these ships require a channel depth of about 40 feet. This only considers port access channel depth as docking depth and pier length may limit the number of slots that can accommodate a deep draft vessel within a port. Once the 45 feet threshold is exceeded, the number of ports that can accommodate such a draft falls dramatically. The building of larger containerships, namely the post-Panamax plus class (draft of about 45 feet), thus has limitations in terms of ports that could be serviced.