River Tees (case study)

• The River Tees has a large estuary with mudflats and sandbanks in the lower course
• Where is the River Tees situated?

  North-East England.
• Where is it's source found?

  The source is located at Cross Fell, in the Pennine Hills. It is situated 893m above sea level.
• What happens in the upper course of the river?

  The river flows over hard, impermeable rocks. The valley has steep sides, forming a V-shape. The river is still shallow and rocky and very clear. It is turbulent.
• What is situated in the upper course of this river?

  High Force Falls.
• What is the two types of rock in the waterfall?

  Hard rock - Windstone. Soft rock - Limestone.
• What happens at the middle course?

  As the river flows downstream the gradient becomes less steep. The river also begins to erode sideways (lateral erosion) and the river begins to deposit sand and gravel.
• What happens as a result of the lateral erosion?

  This means that the river gets wider, which results in the formation of meanders. There are large meanders around Yarm.
• What county is the River Tees located in?

  Durham
• Which hills are the source of the River Tees in?

  Pennine Hills
• What is the hard rock at the River Tees called?

  Whin sill
• What is the soft rock at the River Tees called?

  Limestone
• What course is the High Force waterfall in?

  Upper course
• How has geology formed the High Force waterfall?

  Limestone has eroded faster than whin sill, leaving a ledge of whin sill that the water flows over
• How does the High Force waterfall retreat?

  Further erosion of limestone causes the whin sill to collapse by gravity and fall into the plunge pool - as this carries on, a gorge is formed
• How is the plunge pool formed?

  When the ledge collapses, it erodes the river bed by abrasion to create a deeper part under the waterfall
• Which courses are floodplains and meanders in?

  Middle and lower course
• How are floodplains formed?

  Increased lateral erosion creates flatter land, meander migration further flattens and widens the floodplains
• Why are the Tees floodplains fertile?

  Near Middlesbrough, regular flooding has deposited fertile silt on the land
• How are levees formed?

  In floods, the larger material is deposited closer to the river as it gets dropped first when the river slows. The deposited material builds banks to create steep edges (levees)
• What are meanders?


  Large bends in a river
• How are meanders formed?


  The faster current on the outside bend due to river depth erodes more, forming river cliffs. The slower current on the inside bend due to shallow depth causes material to be deposited, forming slip-off slopes.
• How many reservoirs are in the upper course of the Tees?

  9 including Cow Green, altogether hold 41 million cubic metres of water
• Benefits of reservoirs


  Successfully controls the volume of water industries and homes receive, stores rainfall to prevent flooding of river
• Drawbacks to reservoirs


  Very expensive to build, can trap sediment, affecting river load in the lower course
• How does afforestation in the upper course work?

  Trees soak up water from the soil, preventing mass movement as the soil is held together, reduces river discharge to prevent flooding.
• Benefits of afforestation


  Reduced risk of flooding, looks natural, environmentally friendly
• Drawbacks of afforestation


  Less space for farming in the upper course
• How does the Tees Barrage in the lower course work?

  Stops and controls the water levels rising when the sea is at high tide to prevent flooding
• Benefits of Tees Barrage

  Prevents local flooding, riverside land can be built on
• Drawbacks of Tees Barrage

  Very expensive to build & maintain, needs to be maintained constantly following increased sea level rise due to global warming
• How much did the Yarm defences cost?

  £2.1 million
• What defences were used at Yarm?

  Concrete walls to raise river banks

  Earth banks protecting schools

  Redirecting tributaries away from the town centre
• Benefits of Yarm defences

  Prevents flooding, less flood damage to buildings in inner town, reduced damage costs to individuals and insurance companies
• Drawbacks of Yarm defences

  Affects river load, so natural land forms such as levees aren't able to be made