Drainage basin

The River Tees in north-east England is a distinctive river landscape because it connects steep upland valleys and waterfalls with broad lowland floodplains and a heavily modified estuary. It flows approximately 137 km, from Cross Fell in the Pennines to the North Sea near Middlesbrough. Its drainage basin covers about 1,834 km²: rainfall falling within this area can reach the Tees through its tributaries or by flowing over and through the ground.

Rainfall supplies water, the underlying rocks influence erosion and drainage, and material moves down valley sides into the river. These processes connect the surrounding drainage basin—the land drained by a river and its tributaries—to the channel.

The drainage basin therefore collected rainfall and delivered it rapidly towards the village. This left little time for evacuation as river levels rose.