Case study: river basin - River Tees River Tees The River Tees is located in the North of England. The source of the River Tees is located in the Pennines and the river flows east to its mouth where it joins the North Sea. Upper course The upper course has hard impermeable rocks. Here, vertical erosion has formed a V-shaped valley . High Force, the UK's largest waterfall at 21 metres high, is located in the upper course. Here, a layer of hard resistant igneous rock called the Whin Sill (or Whinstone) lies over a layer of softer rocks (sandstones and slates) which erode more easily. High Force waterfall Middle course © Crown copyright and database rights 2015 Ordnance Survey Lower course Near Yarm, the meanders in the lower course are much larger, and oxbow lakes have formed. In this area there are also levees which have formed when the river has flooded. The River Tees has a very large estuary with mudflats and sandbanks which supports wildlife in the area. Sites such as Seal Sands are protected areas. The River Tees estuary and its mudflats Human activity There is a wide range of human activity in the Tees river basin. Transport and settlement - the Tees has been an important route way for centuries, and towns such as Yarm owe their existence to trading on the river. Water supply - Cow Green reservoir supplies the city of Middlesbrough. Farming - Sheep farming in the upper course. Tourism - The Pennine Way, High Force waterfall etc. Industry - the wide, flat valley floor and tidal estuary have been extensively developed for heavy industries, including steel (recently terminated), oil, gas and petro-chemical industries.