River Landforms: Waterfalls, Meanders & Levees
Why Each Course Has Its Own Landforms
Different parts of a river create different landforms because the dominant process is different. The upper course is shaped by vertical erosion (cutting down), the middle course by lateral erosion (cutting sideways), and the lower course by deposition (dropping the load). You need one named UK example for each major landform — learn the chain, then learn one place name for each.
Upper Course: Interlocking Spurs and Waterfalls
In the upper course the river has not got enough energy to cut sideways through the hills, so it weaves between them. The result is interlocking spurs — ridges that project from alternate sides of the valley, with the river snaking between them. The view down the valley looks like fingers interlocking from each side.
A waterfall forms where a band of hard rock lies over softer rock. The softer rock erodes faster, undercutting the hard rock above. The river falls vertically into a deep pool at the base — the plunge pool — which is itself eroded by hydraulic action and abrasion. Over thousands of years the hard rock above eventually collapses without support, and the waterfall retreats upstream, leaving a steep narrow gorge behind it.
1. A river crosses a band of hard rock lying over softer rock.
2. The softer rock is eroded faster, leaving the hard rock as an overhanging step.
3. The river plunges over the step. Hydraulic action and abrasion erode a deep plunge pool at the base.
4. The plunge pool undercuts the hard cap rock, which eventually collapses without support.
5. The waterfall retreats upstream, leaving a steep, narrow gorge of recession behind it. High Force on the River Tees in County Durham is a clear UK example.
High Force on the River Tees is a 21 m waterfall where the hard Whin Sill rock lies over softer limestone. The plunge pool below is over 6 m deep. The waterfall has retreated upstream, leaving a 700 m gorge.
Middle Course: Meanders and Ox-Bow Lakes
Once the gradient flattens, the river starts swinging from side to side. The result is a meander. On the outer bank the water flows fastest because the channel is deeper there; this energy erodes the bank into a steep river cliff. On the inner bank the water flows slowly because the channel is shallow; the river drops material here, building a gentle slip-off slope of sand and shingle.
Over time the meander becomes more and more curved as erosion deepens the outer bend and deposition builds the inner one. Eventually two outer bends erode towards each other; during a flood the river cuts across the narrow neck between them. The new straighter channel takes over and the abandoned meander loop becomes an ox-bow lake. Ox-bow lakes are common on the lower River Severn near Worcester, and on the River Cuckmere in East Sussex.
Lower Course: Flood Plains, Levees and Estuaries
Near the mouth, the river spreads out across a wide flat valley. When the river floods, water spreads beyond the channel. As it does so it slows down, and the coarsest material is dropped first — right next to the channel. Over hundreds of floods this builds levees — raised natural banks that line the river. Beyond the levees, the floodwater drops finer silt across the wider flood plain, creating fertile farmland.
At the mouth the river meets the sea and slows further still. If the tide is strong it forms a wide estuary — the lower Severn, Thames and Humber are good UK examples. The fresh and salt water mix; mudflats and salt marsh develop along the banks. Estuaries are vital ports (Liverpool, Bristol, Hull) and important wildlife habitats.
1. Lateral erosion deepens the outer bends of two neighbouring meanders, and deposition builds up the inner bends.
2. The neck of land between the two meanders becomes narrower over time.
3. During a flood the river has the energy to cut straight across the narrow neck.
4. The new shorter channel takes over; deposition seals off the old meander loop.
5. The abandoned curve becomes an ox-bow lake, gradually drying out as silt fills it in.
On a meander, water flows fastest on the outer bend, eroding it into a steep river cliff. On the inner bend the water is slow, so material is deposited as a gentle slip-off slope.
A Worked UK Example: The River Tees
The Tees rises in the Pennines and flows 137 km to the North Sea at Middlesbrough. In its upper course on Cross Fell it shows interlocking spurs and the High Force waterfall. In its middle course near Yarm it loops in textbook meanders. Near its mouth it widens into a large estuary lined with industrial complexes. One river demonstrates almost every fluvial landform in the course, which is why exam questions sometimes ask for landforms 'along' a named UK river.