Question

what led to the development of new port cities at the cost of the decline of the old ones?​

Answer 1

After World War II many ports escaped from their metropolitan straitjackets and developed new ports with access to deep water and adequate land areas. Sometimes the existing inner-city facilities were no longer required for commercial port operations and fell into decay.

Answer 2

As the cities grew, ports increasingly "competed" for land with industry, housing, and other urban uses. After World War II many ports escaped from their metropolitan straitjackets and developed new ports with access to deep water and adequate land areas.