Edexcel GCSE Geography B (1GB0) — UK Physical Landscapes
Every drop of rain that falls on a mountain undergoes a massive transformation before it reaches the sea. A river's journey is mapped using two main tools: the long profile (a line showing the concave gradient from source to mouth) and the cross profile (a 2D "slice" through the valley and channel).
To understand a river system like the River Tees, we must compare its three main stages. While they look very different, they share crucial similarities: all stages sit within the same drainage basin, operate under the same hydrological cycle, and feature a defined channel with a thalweg (line of fastest flow) and a wetted perimeter (the contact area between water and the channel bed/banks). Fluvial processes like erosion, transportation, and deposition occur in all three courses, though their dominance shifts.
| Feature | Upper Course (e.g., Upper Teesdale) | Middle Course (e.g., Barnard Castle) | Lower Course (e.g., Stockton/Yarm) |
|---|---|---|---|
| Gradient | Steepest gradient; river flows downhill rapidly. | Flatter, gentler gradient. | Very flat, smooth gradient approaching sea level. |
| Valley Shape | Steep-sided V-shaped valley with interlocking spurs. | Wider valley with gently sloping sides and early floodplains. | Extremely wide, flat floodplains bounded by levees (Broad/U-shaped). |
| Erosion Type | Vertical erosion dominates, cutting downwards into the bedrock. | Lateral erosion dominates, widening the valley sideways. |
| Minimal erosion; mostly lateral erosion on meander bends. |
| Channel Width | Narrow (often m). | Wider ( m). | Widest ( m, reaching m+ at the estuary). |
| Channel Depth | Shallow (often m). | Deeper ( m). | Deepest ( m). |
| Velocity | Low average velocity ( m/s) due to high friction from angular boulders. | Increasing velocity as the channel becomes more efficient. | Highest average velocity ( m/s, up to m/s) due to low friction. |
The changes outlined above follow the Bradshaw Model. This theoretical model states that as you move downstream, discharge, occupied channel width, channel depth, and average velocity all increase.
Conversely, the river's slope gradient, channel bed roughness, and the size of the load particles decrease. The load becomes smaller and rounder downstream due to the processes of attrition (rocks smashing together) and abrasion (rocks scraping the bed and banks).
Discharge is the total volume of water passing a specific point per second, measured in cumecs (). It is calculated by multiplying the cross-sectional area of the channel by its mean velocity.
Where:
A geographical survey of a river in its middle course reveals an average depth of 1.5 m and a width of 12.0 m. The mean velocity of the water is 0.6 m/s. Calculate the river's discharge.
Step 1: Calculate the cross-sectional area ().
Step 2: Substitute the area and velocity into the discharge equation.
Step 3: Calculate the final answer with units.
Trying to imagine a 3D landscape from a flat piece of paper is a crucial geographical skill. Ordnance Survey (OS) maps use contour lines (or isolines) to show relief (the shape and height of the land). Maps typically use a 1:25,000 or 1:50,000 scale, with a contour interval of 5 m or 10 m between each line. Exact heights are marked with a dot and number, known as a spot height.
To identify valley shapes from contour patterns, look at the spacing and direction of the lines. Closely spaced contours indicate a steep slope, while widely spaced contours mean gentle, flat land. V-shaped contour lines that point uphill (towards higher ground) represent valleys, whereas V-shapes pointing downhill indicate spurs.
To draw a cross-profile from an OS map, follow this step-by-step method:
Water alone is rarely enough to create a dramatic waterfall; the underlying rock dictates where these sudden drops appear. A river's long profile is heavily influenced by lithology (the physical characteristics of the bedrock).
Resistant rock (typically older, igneous rocks like granite or dolerite) is hard to erode. When a river flows over resistant rock, it creates steeper gradients, narrow gorges, and "steps" in the profile. In contrast, less resistant sedimentary rocks (like clay or limestone) erode quickly, resulting in gentler, flatter gradients. This uneven rate of wear is called differential erosion.
Rock permeability also plays a role. Impermeable rocks prevent water from soaking into the ground, increasing surface runoff and river discharge, which in turn accelerates erosion. Permeable rocks allow water to infiltrate, sometimes leaving surface channels completely dry.
Geographers use British Geological Survey (BGS) maps alongside OS maps to analyse why specific landforms exist. By finding the same coordinate location on both maps, you can correlate changes in the river's gradient with underlying rock bands.
Where a river transitions from a band of highly resistant rock to a band of softer rock, the softer rock erodes much faster. This creates a sharp change in gradient known as a knick point, which often manifests as a waterfall or rapids. For example, on the River Tees, the spectacular 21 m High Force Waterfall formed exactly where the resistant igneous Whin Sill (dolerite) overlays softer, less resistant sedimentary limestone and sandstone.
Students often incorrectly assume that velocity is highest in the upper course because the water looks turbulent and 'fast' over rapids; however, average velocity actually increases downstream as the channel becomes deeper, wider, and smoother, creating less friction.
When asked to 'Compare' river courses in an exam, ensure you state both differences (such as gradient or width) AND similarities (such as the presence of a channel, a thalweg, or the occurrence of fluvial processes) to access top marks.
If drawing a cross-profile from an OS map, always join your plotted points with a smooth freehand curve; examiners will actively deduct marks if you use a ruler to connect the points with straight lines.
When analysing BGS geology maps to explain river profiles, you must explicitly name the rock types from the key (e.g., 'igneous dolerite' or 'sedimentary limestone') and link their differing resistances to the formation of knick points.
Long profile
A line representing the gradient of a river from its source to its mouth, typically forming a concave curve.
Cross profile
A diagrammatic cross-section showing the shape of a river valley and channel at a specific point.
Thalweg
The line of fastest flow within a river channel.
Wetted perimeter
The total length of the river bed and banks that are in direct contact with the water.
V-shaped valley
A steep-sided, narrow valley found in the upper course of a river, formed predominantly by vertical erosion.
Vertical erosion
Downward erosion that deepens the river channel, most dominant in the upper course.
Lateral erosion
Sideways erosion that widens the river valley and channel, dominant in the middle and lower courses.
Bradshaw Model
A theoretical model that describes how river characteristics, such as discharge and velocity, change from source to mouth.
Discharge
The volume of water passing a specific point in a river per second, measured in cubic metres per second (cumecs).
Attrition
An erosion process where rocks and pebbles carried by the river collide and break into smaller, smoother, and rounder pieces.
Abrasion
An erosion process where the river's load acts like sandpaper, scraping and wearing away the bed and banks.
Contour lines
Lines on a map that join points of equal height above sea level, used to determine the steepness of the land.
Relief
The physical shape of the landscape, including its height and the steepness of its slopes.
Contour interval
The vertical distance or difference in elevation between two adjacent contour lines.
Spot height
A specific point on a map marked with a dot and a number to indicate its exact height above sea level.
Lithology
The physical characteristics of rock types, including their hardness and resistance to erosion.
Resistant rock
Hard rock, often igneous or metamorphic, that is difficult for a river to erode.
Differential erosion
The process where rocks of varying hardness erode at different rates, often creating waterfalls or uneven landscapes.
Permeability
The ability of a rock or soil to allow water to pass through its pores or joints.
Knick point
A sudden, sharp change in the gradient of a river's long profile, typically marking the location of a waterfall.
Put your knowledge into practice — try past paper questions for Geography B
Long profile
A line representing the gradient of a river from its source to its mouth, typically forming a concave curve.
Cross profile
A diagrammatic cross-section showing the shape of a river valley and channel at a specific point.
Thalweg
The line of fastest flow within a river channel.
Wetted perimeter
The total length of the river bed and banks that are in direct contact with the water.
V-shaped valley
A steep-sided, narrow valley found in the upper course of a river, formed predominantly by vertical erosion.
Vertical erosion
Downward erosion that deepens the river channel, most dominant in the upper course.
Lateral erosion
Sideways erosion that widens the river valley and channel, dominant in the middle and lower courses.
Bradshaw Model
A theoretical model that describes how river characteristics, such as discharge and velocity, change from source to mouth.
Discharge
The volume of water passing a specific point in a river per second, measured in cubic metres per second (cumecs).
Attrition
An erosion process where rocks and pebbles carried by the river collide and break into smaller, smoother, and rounder pieces.
Abrasion
An erosion process where the river's load acts like sandpaper, scraping and wearing away the bed and banks.
Contour lines
Lines on a map that join points of equal height above sea level, used to determine the steepness of the land.
Relief
The physical shape of the landscape, including its height and the steepness of its slopes.
Contour interval
The vertical distance or difference in elevation between two adjacent contour lines.
Spot height
A specific point on a map marked with a dot and a number to indicate its exact height above sea level.
Lithology
The physical characteristics of rock types, including their hardness and resistance to erosion.
Resistant rock
Hard rock, often igneous or metamorphic, that is difficult for a river to erode.
Differential erosion
The process where rocks of varying hardness erode at different rates, often creating waterfalls or uneven landscapes.
Permeability
The ability of a rock or soil to allow water to pass through its pores or joints.
Knick point
A sudden, sharp change in the gradient of a river's long profile, typically marking the location of a waterfall.
