The River Tees is in Northern England. Its source is in the Pennines at Cross Fell. It then flows 130km to its mouth at Teesside, into the North Sea. Its drainage basin is 1,800km2.
Parts of the River Tees are very natural, whereas other parts have been affected by humans.
How are geomorphic processes shaping river basins?
The upper section
This section of the river is characterised by mountains, hills and steep slopes.
V-shaped valleys are found in the upper course of the river near the source. The upper course of the River Tees runs through moorlands. The river descends quickly through the valleys giving the water enough energy to erode the rock creating steep-sided v-shaped valleys. The river itself has large rocks in it over which the water flows. Abrasion from rocks in the bed of the river scrape away, vertically eroding the bed.
High Force waterfall is one of the most distinctive features of the upper course of the River Tees.
High Force was formed due to a very resistant igneous rock called dolerite (locally known as Whin Sill overlying a softer rock called limestone. The softer rock will erode (mainly due to hydraulic action) quicker than the harder rock on top. This results in undercutting, leaving the hard rock overhanging. Eventually the harder rock will be unsupported and will collapse. This means that the waterfall gradually moves upstream, leaving a gorge.
The middle section
As the River Tees enters its middle section, tributaries have added more water. This means that the river gets wider and deeper. In addition to this, attrition has eroded the large rocks in the upper section to smaller pebbles. This all means that there is less friction in the river, so the river can flow faster. When rivers flow faster, they have more energy. This results in more hydraulic action. This is when meanders start to form, with lateral erosion and a flood plain starts to develop. This can be seen around Barnard Castle.
The lower course
As the River Tees enters the lower course the meanders get bigger and the flood plain gets wider.
This is evident between Darlington and Yarm.
In some places the meanders develop into ox-bow lakes.
The final feature found in the Lower Section is levees.
The River Tees enters the North Sea through its estuary.
How do climate and geology influence geomorphic processes?
Geology: Cross Fell in the upper section is mainly made up of limestone. Water will drain through limestone, so there is little surface water. Limestone also reacts with rainwater, so there will be chemical weathering. The resistant dolerite overlaying the limestone at High Force waterfall impacts on the rates of hydraulic action at the base of the waterfall.
Climate: In the upper section the cold, wet climate results in freeze thaw weathering on the steep valley sides. This breaks the rock, which will end up in the river. This can result in increased abrasion and vertical erosion. High rainfall rates in the Pennines can increase river levels, resulting in more erosion and flooding further down stream.
How is human activity, including management, working in combination with geomorphic processes to shape the landscape?
Cow Green reservoir: This has controlled the river, with a build up of sediment behind the dam itself. The river downstream of the dam will have less sediment, so will flow faster. This means that erosion rates could increase.
Yarm: Like many of the towns along the course of the river, humans have introduced flood prevention schemes. Yarm implemented a flood prevention scheme costing £2.1 million. Concrete walls along the river bank were build to get the water through the town quicker. This can increase erosion levels. To counteract this gabions (baskets with stones in) were introduced to reduce erosion. Embankments were raised so the river can hold more water. Further downstream, flooding is more likely.
Teesside: The river Tees enters the North Sea through its estuary. In this area the river has been greatly modified by humans. A large meander (the Mandale Loop) was cut off, shortening the river by 4km, meaning the river flows faster to the sea. The river has been dredged to keep it clear of sediment and to ensure large ships can access the heavy industry and oil refineries in the area. This means that the river will flow faster. The dredged material was also used as part of the land reclamation.
In 1995 the Tees Barrage was build at a cost of £54 million. This is to prevent flooding, particularly at high tide and in times of storms.