As the River Tees enters its middle course, the landscape and river processes undergo significant changes. This section of the river is characterized by a wider valley, a more gently sloping gradient, and the beginnings of lateral erosion.

The middle course of the River Tees showcases classic examples of meander formation, demonstrating the river erosion and deposition processes that shape this part of the river system. Meanders are sinuous bends in the river channel that develop through a combination of erosion and deposition.

The process of meander formation in the River Tees involves:

1. Faster flow on the outside of bends leading to increased erosion $primarily through hydraulic action and abrasion$.
2. Slower flow on the inside of bends resulting in deposition.
3. Over time, these processes cause the meanders to become more pronounced.

Vocabulary: Hydraulic action is the erosive force of water hitting the river banks, while abrasion is the wearing away of the banks by sediment carried in the water.

As meanders continue to develop, they can eventually form oxbow lakes. This occurs when the neck of a meander becomes so narrow that the river cuts through during a flood event, abandoning the original curve of the channel.

Example: The town of Yarm, located on the River Tees, is situated within a meander. While this provided defensive advantages historically, it has limited the town's growth in modern times.

The middle course of the River Tees also begins to develop a floodplain. This flat area adjacent to the river channel is formed by the deposition of sediment during flood events. The floodplain of the Tees is noted for its fertility, making it valuable for agriculture.

Highlight: The fertile floodplain of the River Tees supports intensive agriculture, demonstrating the economic importance of river landforms.

The lower course of the River Tees is characterized by a gentle gradient, a wide and flat valley, and significant deposition. This section of the river showcases the final stages of river erosion and deposition processes before the Tees reaches its mouth at the North Sea.

Key features of the lower Tees include:

1. Wide Floodplains: The river valley in the lower course is very wide and flat, with extensive floodplains on either side of the channel. These floodplains are formed by the deposition of fine sediment $silt$ during flood events.

Definition: A floodplain is the flat area adjacent to a river channel, formed by the deposition of sediment during floods and subject to periodic flooding.

2. Levees: Natural embankments along the river banks, formed by the deposition of coarser sediments during floods. Levees are a classic example of how rivers shape their own channels through deposition.
3. Meanders: The lower course of the Tees continues to feature meanders, though they are typically larger and more sweeping than those in the middle course. These meanders can migrate across the floodplain over time, contributing to the widening of the valley.
4. Estuary: As the Tees approaches the North Sea, it forms an estuary - a partially enclosed coastal body of water with one or more rivers flowing into it and a free connection to the open sea.

Vocabulary: An estuary is a transitional zone between river environments and maritime environments, subject to both marine and riverine influences.

The estuary of the River Tees is characterized by:

• Tidal influences, with water levels and flow directions changing with the tides
• Mixing of fresh and salt water
• Deposition of fine sediments, forming mudflats
• Rich biodiversity, providing important habitats for various species

Highlight: Estuaries, like that of the River Tees, are ecologically significant areas, serving as nurseries for many marine species and important stopover points for migratory birds.

The lower course of the River Tees also showcases the human impact on river systems. The area around the mouth of the Tees, particularly Middlesbrough, has been heavily industrialized, with port facilities and chemical plants altering the natural estuarine environment.

Example: The Tees Barrage, an artificial barrage across the river near Stockton-on-Tees, was built to control tidal flow and prevent flooding upstream, demonstrating how human intervention can modify river processes.

The River Tees provides an excellent case study of a complete river system, showcasing the changing characteristics and processes from source to mouth. By examining the Tees, we can observe how river erosion and deposition processes evolve along the course of a river.

Key points to remember about the River Tees:

1. Upper Course: Steep gradient with V-shaped valleys Dominated by vertical erosion Features like High Force waterfall and interlocking spurs
2. Middle Course: Wider valley with a more gentle gradient Development of meanders and the beginnings of a floodplain Balance between erosion and deposition
3. Lower Course: Very wide, flat valley with extensive floodplains Dominated by deposition Features like levees and an estuary at the mouth

Highlight: The River Tees demonstrates how a single river can exhibit dramatically different characteristics along its course, shaped by the interplay of erosion, transportation, and deposition.

The study of the River Tees also illustrates the interaction between physical processes and human activities. From the agricultural use of floodplains in the middle course to the industrial development near the estuary, the Tees showcases how rivers shape and are shaped by human settlement and economic activities.

Quote: "The River Tees runs from Cross Fell to the North Sea, providing a textbook example of how rivers change from source to mouth."

Understanding the processes and landforms of the River Tees can help in the management of other river systems, informing decisions about flood control, conservation, and sustainable development in river basins around the world.

This section examines flood causes, mechanisms, and analysis tools.

Definition: Hydrographs plot river discharge after storms, showing rainfall and water flow relationships.

Vocabulary: Flash floods are sudden flooding events typically occurring in summer due to intense rainfall.

Flooding factors include:

• Physical: Precipitation, geology, relief
• Human: Land use changes, urbanization
• Basin characteristics: Size, drainage density, rock type

This section explores structural approaches to river management and flood control.

Definition: Hard engineering involves built structures and physical interventions in river systems.

Key strategies include:

• Dams and reservoirs for water control
• River straightening for efficient flow
• Embankments for increased capacity
• Flood relief channels for overflow management

Highlight: While effective, hard engineering can be costly and environmentally impactful.

Soft engineering focuses on working with natural processes for flood management.

Example: Afforestation benefits:

• Natural flood control
• Carbon absorption
• Habitat creation
• Cost-effective implementation

Vocabulary: Floodplain zoning involves strategic land use planning to minimize flood risk to important infrastructure.

The upper course of the River Tees is characterized by steep gradients and powerful erosional forces. This section of the river showcases textbook examples of river erosion and deposition processes.

High Force, the most prominent feature of the upper Tees, is a spectacular waterfall with a 20-meter drop. The formation of High Force illustrates the process of waterfall creation and retreat. A resistant band of igneous rock $dolerite$ overlays softer limestone, leading to differential erosion.

Vocabulary: Differential erosion occurs when softer rock erodes more quickly than harder rock, creating distinct landforms.

The process of waterfall formation and retreat involves several steps:

1. The river flows over the hard dolerite rock.
2. The underlying softer limestone is eroded more quickly through hydraulic action and abrasion.
3. This creates an overhang of the harder rock.
4. Eventually, the overhang collapses, and the waterfall retreats upstream.
5. This process continues, forming a gorge.

Example: High Force waterfall on the River Tees drops 20 meters and has formed a gorge through this process of erosion and retreat.

Another notable feature of the upper Tees is the presence of V-shaped valleys. These form due to the dominance of vertical erosion in the upper course, where the river has high energy and flows over hard, impermeable rocks.

Definition: V-shaped valleys are steep-sided valleys typically found in the upper course of rivers, formed by vertical erosion.

The characteristics of interlocking spurs in river valleys are also evident in the upper Tees. These alternating projections of high ground are formed as the river erodes around more resistant rock, creating a zig-zag pattern in the river's course.

Highlight: Interlocking spurs are a key indicator of a river's upper course and demonstrate the river's ability to erode selectively based on rock hardness.