River Landforms

The river did not dig this on its own

You have met the five geomorphic processes: weathering, mass movement, erosion, transport and deposition. And you have probably met the river story too, in which a river erodes, transports and deposits its way from the hills to the sea. ⚠️ NOTICE THAT THE SECOND LIST IS SHORTER THAN THE FIRST, AND THAT ALMOST NOBODY EXPLAINS WHERE THE OTHER TWO WENT. They did not go anywhere. They are doing a different job, in a different place, and it is the job that turns a river into a valley. Here is the sentence almost every student writes, and it is not right. ⚠️ "THE RIVER ERODED THE VALLEY INTO A V SHAPE." Think about where the river actually is. It is a channel at the very bottom, often only a few metres wide. The valley above it can be hundreds of metres across. ⭐ THE WATER IS NOWHERE NEAR MOST OF THE GROUND THAT HAS BEEN REMOVED. IT CANNOT HAVE CUT IT. What happens instead is a collaboration, and it has three parts. The river cuts DOWNWARDS. That is the only direction its erosion works in the upper course, and it makes a slot, not a V. ⚠️ THE SIDES OF THAT SLOT ARE THEN ATTACKED BY WEATHERING, which breaks rock apart where it stands, without moving it anywhere. ⚠️ AND GRAVITY DELIVERS THE LOOSENED MATERIAL DOWN THE SLOPE TO THE CHANNEL. THAT IS MASS MOVEMENT, and it is why the sides lean back instead of standing vertical. The river's final job is simply to carry that material away, which keeps the bottom of the valley clear so the whole process can carry on. ⭐ SO THE V IS MADE BY THREE THINGS WORKING TOGETHER, AND THE RIVER IS ONLY ONE OF THEM. ⚠️ WHICH GIVES YOU A TEST FOR EVERY LANDFORM ANSWER YOU WILL WRITE ON THIS TOPIC: SAY WHICH PROCESS, AND SAY WHERE IT IS ACTING - IN THE CHANNEL, OR ON THE SLOPE.

Two workplaces, five processes

The same five processes you already know, sorted by where they are actually doing their work. The right-hand column is the half the standard river story leaves out.

Tap what the valley shape actually shows

Tap the TWO statements that are true of how a river valley gets its shape.

• The river cuts downwards while weathering and gravity work on the slopes above it
• The river keeps the valley floor clear by carrying away material the slopes deliver to it
• The river erodes sideways across the whole width of the valley to cut the V shape
• Weathering carries broken rock down to the channel

Broken where it lies

Water gets into a crack high on a valley side, freezes overnight and splits the rock apart. The fragments stay exactly where they are until a wet spell sends them sliding down to the river. Which processes are these, in order?

• Weathering, then mass movement: the rock was broken in place, and gravity moved it afterwards
• Erosion, then transport, because the rock was worn away and then carried
• Weathering, then erosion, since the river ends up carrying the fragments
• Mass movement, then erosion

Five words for what happens where

Five terms, each defined by what it is. No landform is named here.

Match each landform to which process acts where

Two that follow from the two workplaces

Select the TWO statements that follow from how a valley is actually shaped.

• The slopes and the channel depend on each other, since the slopes supply material and the channel removes it
• Weathering can break a great deal of rock without moving any of it at all
• The river must erode sideways across the full width of the valley to produce a V shape
• Once a valley has formed, weathering and mass movement stop acting on it

Writing a landform answer that earns its marks

You already have the habit of writing a landform as a chain rather than a description. This topic adds one word to that habit, and it is the word that separates the top band. ⭐ WITH EVERY PROCESS YOU NAME, SAY WHERE IT IS ACTING. Not "erosion widens the valley", which leaves an examiner unsure whether you know which erosion, or where. ⚠️ "LATERAL EROSION UNDERCUTS THE SLOPE AT THE FOOT OF THE VALLEY SIDE, AND WEATHERING AND MASS MOVEMENT THEN RETREAT THE SLOPE ABOVE IT" names two processes, two places, and the link between them. Same length. Several more marks. ⚠️ AND KEEP WEATHERING AND EROSION APART IN YOUR WRITING, BECAUSE EXAMINERS TEST THE DIFFERENCE DIRECTLY. Weathering breaks rock in place. Erosion wears rock away by something moving past it. If nothing is moving, it is not erosion. ⭐ NOW THE STRUCTURE FOR A LONGER ANSWER, WHICH IS JUST THE CHAIN WITH THE PLACES PUT IN. What is the rock doing before anything happens to it. Which process acts on it first, and where. What does that leave behind. Which process acts next, and where. And what is the landform that results. ⚠️ EVERY LINK IS A MARK, AND A MISSING LINK IS A MISSING MARK EVEN IF THE CONCLUSION IS RIGHT. Two things specific to this specification. ⚠️ YOU ARE EXPECTED TO USE A NAMED UK RIVER BASIN, so attach your detail to a real place rather than to a generic river. Naming the upland it rises in and the kind of country its lower course crosses is the sort of specific that earns credit. ⚠️ AND MANAGEMENT IS PART OF THIS SAME SECTION, NOT A SEPARATE SUBJECT. A management question is asking what people have done about the processes you have just described, so the two halves should refer to each other.

One river, from the Welsh hills to the sea

Your named example is the River Severn, the longest river in Britain, and it is useful because it shows every stage on one river. It rises high in the uplands of mid Wales, in wet, exposed country. ⚠️ UP THERE THE CHANNEL IS NARROW AND THE WORK IS DOWNWARDS, cutting into rock, while the slopes on either side are exposed to a great deal of weather. Water gets into the rock, freezes, and breaks it; gravity brings the pieces down; the river takes them away. ⭐ THE STEEP-SIDED VALLEYS UP THERE ARE THE RESULT OF ALL THREE, NOT OF THE WATER ALONE. Follow it down and the balance changes. The gradient eases, the channel begins to swing sideways rather than cut down, and the valley floor widens as it does. Material broken off the hills far upstream is still travelling, getting smaller and rounder as it goes. By the lower course the river is crossing flat country. ⚠️ HERE IT DEPOSITS FAR MORE THAN IT PICKS UP. It winds broadly across its own floodplain, and when it floods it spreads material out across that flat land, which is exactly why the farmland beside it is good and why towns grew up there in the first place. And that is where management enters, as this part of your course requires. Settlements on a floodplain are on a floodplain because of what the river does, so the question is never whether to live with the river but how. ⚠️ HARD ENGINEERING BUILDS SOMETHING: raised banks and walls to keep the water in the channel, and barriers at the places most often flooded. Softer approaches work further up instead, holding water back in the catchment, letting some fields flood deliberately so that towns do not, and planting to slow the rate at which rain reaches the river at all. ⭐ NOTICE THAT THE SOFTER APPROACHES TREAT THE SAME PROCESSES YOU HAVE JUST LEARNED. Slowing runoff is an attempt to change how fast material and water reach the channel, which is the handover between the slopes and the river that this whole module has been about.

Order how a valley side retreats

Put the stages in order, from an intact slope to a wider valley.

• The channel erodes sideways at the foot of the slope, undercutting it
• The slope above is left steeper and less well supported than it was
• Weathering breaks up the exposed rock on that steepened face
• Gravity moves the loosened material down to the bottom of the slope
• The river carries that material away, leaving the foot of the slope clear again
• The slope has retreated, and the valley is wider than it was

Assemble an answer with the places in

Build the sentence an examiner is looking for when asked why a river valley widens downstream.

The valley and channel run

Five questions on which process acts where, and on managing a river. Three lives.

Complete the river landform facts

Wearing that acts downwards and deepens a channel is _____, while wearing that acts sideways and widens it is _____. The movement of loosened material down a slope under gravity is _____. Management that builds a physical structure to control a river is _____.

Three answers to put right

Three pieces of student writing. In each case the mark is in the reasoning, not the verdict.

• An answer reads: "The river eroded the valley into a V shape." Why will that not reach the higher marks?
• A student writes that weathering carried material down the valley side into the river. What needs correcting?
• Asked to evaluate river management, an answer lists three hard engineering schemes and three softer ones without connecting them to anything. How would you improve it?

Explain how a river valley gets its shape

A classmate has learned that rivers erode valleys into V shapes and cannot explain why the valley is so much wider than the river. Write them an explanation, using a named UK river.

• Explain which direction the channel erodes in the upper course, and what that alone would produce
• Explain what weathering does to the valley sides, being clear that it moves nothing
• Explain how the loosened material reaches the river, naming the process responsible
• Explain why the river has to keep removing that material for the valley to go on widening
• Use a named UK river basin to describe how the balance between these processes changes from source to mouth
• Finish by explaining how people manage the river in its lower course, linking at least one approach to the processes you have described