Location and Formation of a UK River Landscape

The River Tees: from Pennine uplands to the North Sea

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.

Its location helps explain its character. The headwaters lie around 754 m above sea level, giving the upper course a steep gradient. Further downstream, the gradient becomes gentler, changing the balance between erosion and deposition. The river therefore provides a connected example of both upland and lowland landscapes rather than a collection of unrelated features.

Location also influences how people use the landscape. Upper Teesdale has open moorland and rough grazing, mainly used for sheep farming. Around Barnard Castle, flatter, fertile floodplains support farming. Towards Stockton-on-Tees and Middlesbrough, urban and industrial land uses become more important. The estuary supports shipping and industry, while its mudflats, including Seal Sands, are important wildlife habitats. This combination creates competing demands for water supply, navigation, flood protection and conservation.

How the upland landscape formed

Near Cross Fell, the Tees has a narrow, shallow channel with a rough bed and large, angular material. Its steep gradient encourages vertical erosion, cutting down into the landscape. This produces steep-sided, V-shaped valleys. Where the young river winds around projecting slopes rather than cutting straight through them, interlocking spurs remain; examples occur near Cauldron Snout.

Rock resistance helps create distinctive interruptions in the river’s profile. Resistant whinstone produces an uneven channel, including rapids between High Force and Low Force. At High Force, resistant Whin Sill dolerite overlies less resistant sandstone and limestone. These rocks do not erode at the same rate.

The softer rocks are worn away more quickly by the force of the water and by rock fragments carried by it. Erosion at the base creates a plunge pool and undercuts the resistant rock above, leaving an overhang. Eventually, the unsupported overhang collapses. Repeated undercutting and collapse cause the waterfall to retreat upstream, leaving a steep-sided gorge behind. The waterfall’s position and development therefore depend on geology as well as flowing water.

How meanders and floodplains developed downstream

Around Barnard Castle, the gradient becomes gentler and the channel wider and deeper. Lateral erosion becomes more important, widening the valley and helping bends, or meanders, develop.

Water flows faster around the outside of a bend, eroding the bank. On the inside, slower water deposits sediment. This combination shifts the bend sideways and downstream over time. Meanders near Barnard Castle are part of the landscape’s continuing development, not fixed features.

Further downstream, between Darlington and Yarm, meanders are larger. Yarm itself occupies a meander loop. As neighbouring outer banks erode, a meander’s neck can narrow. The river may cut through the neck, taking a shorter route; deposition then seals the entrances to the abandoned loop, forming an oxbow lake. Oxbow lakes occur in parts of the lower Tees landscape.

Repeated flooding also builds the lowland landscape. When water spreads beyond the channel, it loses energy and deposits sediment called alluvium. Together with the sideways movement of meanders, this creates broad, flat floodplains. Repeated deposition close to the channel can build raised banks called natural levees. The fertile floodplains are valuable for farming, but their formation also explains why they are exposed to flooding.

Why rainfall can change the Tees so quickly

The upper catchment receives more than 2,000 mm of rainfall annually. This supplies substantial water to the river, but the total rainfall alone does not explain how quickly river levels rise. The condition of the ground matters too.

Impermeable bedrock limits water movement into the rock. For more than six months of the year, upland peat is saturated, so it has little capacity to absorb additional rain. Much of that rain becomes surface runoff and reaches the river rapidly.

The Tees is therefore described as flashy. After heavy rainfall, its level can rise very quickly: the locally known Tees roll or Tees wave can involve a rise of about one metre in 15 minutes. Increased discharge changes the river’s ability to erode banks and transport sediment, so weather can produce rapid changes within a landscape that has developed over much longer periods.

Annual rainfall is climate evidence: it describes the catchment’s longer-term water supply. A particular heavy rainstorm is weather. Seasonal and year-to-year variations in rainfall affect discharge, while the ground’s saturation helps determine how quickly the river responds.

How people have changed this particular landscape

Human activity has altered both the amount of water moving downstream and the shape of the channel. Reservoirs were built in the upper and middle catchment during the 1960s and 1970s to meet growing water demand.

Cow Green Reservoir, completed in 1971, holds about 40,000 million litres. It stores water and regulates downstream flow, rather than allowing all incoming water to pass immediately along the river. It is therefore a major influence on the Tees’s flow regime as well as a visible alteration to the upland landscape.

Navigation needs changed the lower river directly. During the nineteenth century, meanders towards Stockton-on-Tees were bypassed and the channel straightened. The Mandale Cut removed the need to follow a large loop, shortening the route by about 4 km. This made boat journeys easier and shows how an economic purpose can reshape a natural river course.

Flood protection has also modified the landscape. Yarm has flood gates and gabions, while embankments line parts of the river downstream from Middlesbrough. The Tees Barrage, completed in 1995, controls water levels and helps reduce flood risk from storm surges. These interventions reflect the importance of protecting settlements and economic activity along the lower river.

Which factors have been most influential?

The answer depends on what change and what timescale are being considered. Relief and geology are fundamental to the overall landscape: the steep Pennine setting promotes downcutting, while contrasting rock resistance explains High Force and its gorge. Erosion and deposition create and continually adjust the meanders and floodplains downstream.

Rainfall and runoff are especially influential in short-term changes. Heavy rain falling on saturated peat above impermeable bedrock can produce a rapid rise in discharge, increasing erosion, sediment transport and flood risk.

Human intervention is particularly influential where it deliberately overrides natural behaviour. Cow Green regulates flow, the Mandale Cut changed the river’s route, and the barrage controls water levels. The Tees landscape is therefore the outcome of interacting physical and human processes: physical conditions create the river’s opportunities and hazards, and people alter the river in response.

Location and significance

• River Tees, north-east England: Cross Fell in the Pennines → North Sea near Middlesbrough.
• Approximately 137 km long; basin about 1,834 km²; headwaters around 754 m above sea level.
• Upland moorland and sheep grazing → fertile farming floodplains → urban and industrial estuary, with wildlife habitats at Seal Sands.

Formation

• Upper course: steep gradient → vertical erosion → V-shaped valleys and interlocking spurs near Cauldron Snout.
• High Force: resistant Whin Sill dolerite above softer sandstone and limestone → differential erosion → undercutting and collapse → upstream retreat and gorge.
• Barnard Castle: outer-bank erosion and inner-bank deposition develop meanders.
• Lower course: larger meanders between Darlington and Yarm; cut-offs form oxbow lakes. Flood deposition builds floodplains and natural levees.

Main influences on change

• Geology and relief: shape long-term landform development.
• Rainfall and runoff: over 2,000 mm annually upstream; impermeable bedrock and peat saturated for over six months encourage rapid runoff. The flashy Tees can rise about 1 m in 15 minutes.
• Cow Green Reservoir, 1971: stores water and regulates downstream flow.
• Mandale Cut, nineteenth century: shortened the navigation route by about 4 km.
• Tees Barrage, 1995: controls water levels and helps reduce storm-surge flood risk; other defences include those at Yarm and downstream of Middlesbrough.

Overall judgement: physical processes explain the landscape’s underlying form; weather drives rapid changes; engineering directly alters flow and channel shape at particular locations.