Most maritime transport systems are composed of circuitous networks having a nodal hierarchy, including hubs, gateways, and feeders. By their nature, ports are associated with three main types of risks:
- Concentration. A large share of the traffic can become concentrated in a small number of ports, implying that if a disruption occurs at a hub or a gateway, the impact could be significant.
- Substitutability. If the option of using a specific hub or gateway is temporarily removed, what is the available range of options? The less likely a substitution is, the higher the associated risk.
- Dependence. This represents the share of hinterland or feeder traffic that is associated with a single hub (A) or gateway (B). High levels of dependence are associated with vulnerability as they concern significant cargo volumes that are more difficult to substitute. This is particularly the case for hinterlands related to a single port and with few, if any, options.
Large transshipment hubs (A) and gateways (B) are particularly representative of this vulnerability, as the scale and connectivity advantages they are built on can become a vulnerability if they are disrupted in a significant manner.