River long & cross profiles, including the Bradshaw model

Summary

This video explores the long and cross profiles of rivers, highlighting changes in river characteristics from the source to the mouth. It explains the river's journey through the upper, middle, and lower courses, focusing on gradients, erosion, and deposition. The Bradshaw Model is introduced to show how factors like discharge, velocity, and load size evolve downstream. The video also covers key landforms such as waterfalls, meanders, and floodplains, providing a clear visual understanding of river processes and their impact on landscapes.

Takeaways

• 📉 The river long profile represents the journey of the river from its source (start) to its mouth (end), decreasing in height as it moves downstream.
• 🏞️ The upper course of a river is characterized by steep gradients due to its location in mountainous areas with vertical erosion.
• 🌄 The middle course of the river has a gentler slope and involves both vertical and lateral erosion, causing the river to widen.
• 🌊 The lower course is flat and features wide channels due to significant lateral erosion and deposition near the mouth.
• 🔪 The river cross profile refers to a slice across the river, showing how the valley shape and channel size change from upper to lower course.
• 📈 According to the Bradshaw model, as a river travels downstream, characteristics like discharge, channel depth, and velocity increase.
• ⚒️ Erosion decreases as the river moves downstream, with more erosion in the upper course and less in the lower course, where deposition is higher.
• 🚜 Transportation of sediments increases from source to mouth, with larger boulders in the upper course and finer materials like sand and clay in the lower course.
• ⏩ River velocity increases downstream, even though the surface water may not appear to move quickly, the volume of water contributes to the speed.
• 🏞️ Key landforms include waterfalls and V-shaped valleys in the upper course, meanders and oxbow lakes in the middle course, and floodplains, levees, and estuaries in the lower course.

Q & A

What is a river long profile?

A river long profile is a line representing the course of a river from its source to its mouth, showing the gradient and how the river's height decreases as it travels downstream.

What are the key features of a river in its upper course?

In the upper course, the river has a steep gradient, flows through mountainous or highland areas, and has a small stream or tributary stage with significant vertical erosion.

How does the river change in the middle course compared to the upper course?

In the middle course, the gradient becomes less steep, the river channel widens, and both lateral (sideways) and vertical erosion occur. The river holds more water due to the addition of tributaries.

What characterizes the lower course of a river?

In the lower course, the river has a wide and deep channel, with a gentle slope or flat valley. The water volume is at its highest due to the many tributaries joining, and there is significant lateral erosion and deposition.

What is a river cross profile, and how does it differ from a long profile?

A river cross profile is a cross-sectional view of the river, showing the shape of the river valley and channel from one side of the riverbank to the other. Unlike the long profile, which shows changes in gradient over the river's course, the cross profile highlights the depth and width of the river at different stages.

How does the Bradshaw model describe changes in a river's characteristics from source to mouth?

The Bradshaw model explains how various river characteristics, such as discharge, channel depth, and velocity, change as the river moves from source to mouth. For example, discharge and velocity increase downstream, while erosion shifts from vertical to lateral, and the size of transported material decreases.

What are the main types of erosion in a river's course?

In the upper course, vertical erosion dominates, cutting deep valleys. In the middle course, both vertical and lateral erosion shape the river. By the lower course, erosion decreases, and deposition becomes more prominent.

What is the significance of transportation and deposition in a river system?

Transportation involves the movement of sediment within the river, which increases from the upper to lower course. Deposition is the process of sediment being dropped, which also increases downstream, creating landforms such as estuaries and deltas.

How does load size change from the upper to the lower course of a river?

In the upper course, large boulders and rocks are common. In the middle course, the load size decreases to smaller rocks and pebbles. By the lower course, the load consists of fine materials such as sand, silt, and clay.

What river features are typically found in the upper, middle, and lower courses?

In the upper course, features include waterfalls, gorges, and V-shaped valleys. In the middle course, meanders and oxbow lakes are common. In the lower course, floodplains, levees, estuaries, and deltas are typical features.