river in the English Midlands. It rises in the county of Staffordshire and, after flowing southeastward, northeastward, and then northward for 168 miles (270 km), enters the Humber estuary 40 miles (65 km) from the North Sea. Its drainage basin covers more than 4,000 square miles (10,000 square km). At Alrewas the high ground of its upper valley recedes, and the Trent flows in a broad floodplain. Its fall below Newark is very slight. The upper Trent itself is a comparatively small stream and provides much less water than its powerful tributaries (the Churnet, Dove, and Derwent) from the Peak District. The Trent is tidal for 50 miles (80 km) up to Cromwell Lock, 3 miles (5 km) below Newark, and at spring tide a bore known as the eagre develops, with a wave front of 3 to 4 feet (about 1 m). Considerable quantities of bulk oil are still transported upstream on the Trent from Hull. Of the canals leading from the Trent, only the Sheffield and South Yorkshire Navigation and the Foss Dyke to Lincoln are of much importance today, and the once-famous Trent and Mersey Canal is little used.