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 possible a substitution is, the higher is the associated risk.
- Dependence. This represents the share of hinterland or feeder traffic that is associated with a single hub or gateway. 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 associated with a single port and with few if any options.
Large transshipment hubs and gateways 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.