This large estuary on Great Britain’s eastern coastline is formed from the confluence of the Ouse and Trent rivers. It discharges about 66,000 gallons (250,000 liters) of water per second into the North Sea, the largest input from any British river into this sea. After the end of the last ice age, when sea levels were much lower, the Humber was a river that flowed up to 30 miles (50 km) past the present coastline before reaching the sea.
About 3.6 million cubic feet (100,000 cubic meters) of sediment are deposited in the estuary every year, mainly from offshore by tidal action. Shifting shoals formed by this sediment can obstruct shipping. The estuary’s intertidal areas are productive ecosystems that support a wide range of mollusks, worms, crustaceans, and other invertebrates. These are vital sources of food for birds, especially waders. The estuary also supports a colony of gray seals, and many lampreys pass through it every year.