Final answer:
Cardiff is the city where the River Ely meets the Severn Estuary and Bristol Channel, serving as an important port over the years.
Step-by-step explanation:
The city where the River Ely meets the Severn Estuary and Bristol Channel is Cardiff. Cardiff is the capital of Wales and is situated on the south coast of the country.
It has an important historic port, known as Cardiff Bay, that has been a pivotal area for coal exportation in the past. The area around the Severn Estuary has been key for trade and navigation, influencing the growth and development of Cardiff.