River Tees

Landforms

Geomorphic processes

Human activity

Upper course

Flood management at Yarm

Middle and lower course

Meanders

Rapids

Waterfalls (High Force)

V-shaped valleys

2 rocks of differing resistance, differential erosion occurs as they erode at different rates, creating a height differential. Hard igneous whinstone, soft sedimentary limestone

Steep gradient means river falls with more force, meaning more vertical hydraulic action and abrasion and therefore more vertical erosion

Steep-sided valley is formed

Sides of valley get weathered away (solution, freeze-thaw/onion-skin weathering), and pieces fall down into the river, where they are transported away. As this process occurs, the valley becomes V-shaped

As the height grows, the strength of the water falling onto the lower rock erodes it even faster, undercutting the harder rock and forming a plunge pool

Eventually, the overhanging hard rock cannot hold its own weight and collapses

The waterfall retreats upstream over time

Sides of the river with a higher velocity have higher rates of hydraulic action and abrasion, meaning higher rate of erosion. This cuts into the riverbank and forms a river cliff

Large rocks on the riverbed cause the river to have differing velocities inside of it

Sides of the river with a lower velocity have almost no erosion, and high amounts of deposition of alluvium, meaning this part of the river gets shallower. This eventually forms a slip off slope

Oxbow lakes

Meanders grow over time

When two meanders become very close to each other, occasionally a flood will mean that they connect. After this event occurs a number of times, the river naturally begins to take this more direct route

As the river velocity in the direct route grows, the river velocity in the old meanders diminishes, and over time more and more deposition occurs until eventually the meander is blocked off and the river no longer takes that route.

Floodplains/levees

During a flood, the river loses energy. When the water flows over the banks and deposits material on either side of the banks, the largest material (rocks) is deposited nearest to it, while the finer material such as silt is carried far into the floodplain

After each flood, a new layer of material is deposited

Eventually the material builds up so much that it is elevated well above the floodplain. It has formed a levee

Middle and lower course

Everywhere

Hydraulic action

Deposition

Weathering

Abrasion

Solution

Vertical erosion

Lateral erosion

Cow Green reservoir

Mandale and Portrack cuts

Tees Barrage

A dam controls the water for industries along the river

£2.1million defence scheme

Straightening of the river increases river velocity by reducing friction and slowing bends

£54million barrier keeps the middle course of the river permanently at high tide - no salt water mixes in

Reinforced concrete walls and gabions prevent lateral erosion, therefore stopping damage

Earth embankments to prevent flooding

Improved flood warning systems

Reduces flood risk as the river has more energy and therefore moves faster, emptying water at a faster rate

The river is also dredged (sediment removed from the riverbed), meaning the river capacity is increased, meaning more water can flow, reducing the flood risk. Bedload is decreased

Reduces flood risk in this area as well

Improves water quality and recreational value

Controls the river discharge and therefore velocity, and is therefore able to reduce flood risks downstream

Increases flooding upstream as water cannot flow past it

Flooding behind the dam created a reservoir

Reduces hydraulic action and abrasion, and therefore vertical and lateral erosion

Urbanisation (at Yarm)

Pavements increase surface runoff and decrease infiltration as they are impermeable - this increases flood risks

Deforestation reduces water absorption, increasing flood risks

Embankments and artificial levees reduce flood risks