River Landforms

RIVER LANDFORMS

You should be able to recognise the following landforms on maps or sketches, describe them, explain how they were formed and be aware of their economic consequences.

Annotate Diagram 2.5a to show these river landforms.

source - the point at which a river starts
tributary - a small river / stream which joins the main river
confluence - the point at which a tributary joins the main river
meander - a bend in the river
mouth - the point at which a river enters a loch or the sea

v-shaped valley ...................EROSION / DEPOSITION
waterfall ...................EROSION / DEPOSITION
alluvial fan ...................EROSION / DEPOSITION
flood plain ...................EROSION / DEPOSITION
levees ...................EROSION / DEPOSITION
meanders ...................EROSION / DEPOSITION
ox - bow lake ...................EROSION / DEPOSITION
braiding ...................EROSION / DEPOSITION
delta ...................EROSION / DEPOSITION

Read the following information and delete either erosion or deposition for each of the above landforms.

v-shaped valley
description - This is a valley whose typical cross section is shaped like a 'v'.
(a cross section is the shape that you would walk if you walked down one side of a valley and up the opposite side).
(the long profile is the shape that you would walk if you walked from the river's source to its mouth).
explanation - As the river cuts down into the landscape in an upland area, gravity and mass movements roll material down the valley sides to give the valley a typical 'v' shape.
diagram - Examine the upper course on Diagram 2.5a.

gully - This is a small v-shaped valley. These are a very common feature of the upper stage of a river.

waterfall
description - A steep drop in the bed of a river causing the water in the river to fall vertically.
explanation - Waterfalls occur where a band of harder rock crosses the path of a river. The river is less able to erode this harder rock and leaves it as a step in the river's long profile.
diagram - Examine the following diagrams. (tip! diagrams are often much easier to understand and remember if you colour them in... danger ... do not put so much colour on them that they resemble wallpaper from the 1960's . Simply, lightly colour in the water blue).

alluvial fan
description - This is a 'fan - shaped' mound of alluvium.
explanation - This feature is formed when the speed of flow is suddenly greatly reduced eg when a stream rushing down the hillside reaches the gently sloping valley floor. When this happens, the river is unable to carry much of its load and this alluvium (usually sands and gravels) is laid down in a fan shape.
diagram - Examine Diagram 3.3a (located in Upland Landforms, formed by erosion).

flood plain
description - This is an area of flat land found on either side of a river. This usually becomes wider as the river nears its mouth.
explanation - The flood plain is the area of land which is flooded when a river overflows its banks. In this area layers of alluvium are laid down. The soils are thus thick and fertile and the land is flat.
This area is thus a prime site for what land uses? .................................. and ......................................
What danger would exist at this location ?
.........................................................................................
diagram - Examine Diagrams 2.6c and 2.6d.
Coloured pencils ready ? On both diagrams lightly colour the river blue and the floodplain brown.

river terraces
description - These are areas of flat land (located on either side of the flood plain) which are raised above the flood plain.
Why might this be a better site for a settlement ?
..................................................................................................
explanation - These river terraces used to be the flood plain but the river has cut down deeper and formed a new flood plain at a lower level.
diagram - Examine Diagram 2.6d and colour in the river terraces green.

levees
description - These are mounds of alluvium piled up along the river's edge.
explanation - These are formed by the river depositing the coursest part of its load (pebbles, gravel and sand) close to the river channel when the river floods. This happens because usually when the water overflows the river bank its speed (and therefore its ability to transport alluvium) is greatly reduced.
Sometimes these are built by people in an attempt to prevent the river flooding.
Why should people go to so much trouble and expense to prevent a river flooding ?
diagram - Examine and suitably shade in the following diagram.
Colour in yellow the levees on Diagram 2.6e

meanders
description - These are bends (loops) in the river. explanation - Lateral (sideways) erosion of the river channel results in the river forming a winding pattern. (tip ! if a river or stream has an absolutely straight pattern then it is probably artificial i.e. a canal).
diagram - As the water flows down a river, its speed is faster on the outside of the meander causing erosion and slower on the inside of the meander resulting in deposition.
This is shown in the diagram below. Mark two areas of erosion and two areas of deposition on Diagram 2.6i.

ox - bow lake
description - This is a truncated (cut off) section of a meander in the river channel which forms a 'c' shape.
explanation - This is formed by the loops in a meander eroding the flood plain until eventually the loop in the meander is left cut off from the main river channel.
diagram - Diagram 2.6h shows four stages in the formation of an ox - bow lake.
Examine also Diagram 2.6i.

braiding
description - This is where the river channel is broken up into a number of distributaries.
explanation - As a river slowly meanders across its flood plain, it often deposits material in the 'middle' of its channel. Sand and shingle banks often form small islands in this way.
diagram - Examine Diagram 2.6i.

delta
description - This is a 'D' - shaped area of sandy / muddy sediment built up into the open water where a river meets the sea or a loch.
explanation - Where a river meets the sea or a lake and its speed is slowed down, then deposition on its bed can lead to braiding taking place. This deposition results in the river bed being built up out into the sea or loch.
diagram - If we examine the following diagram, we can see how the delta extends out towards the sea. Colouring in time ........only the water features.

gorge
description - A narrow steep sided valley.
explanation - This feature is formed where a river is cutting through a band of hard rock.
diagram - Examine Diagram 2.6j.

rift valley
description - A valley with a flat floor and steep sides.
explanation - The lowland area of the valley floor has dropped as a result of downward movement along the fault lines.
diagram - Examine Diagram 2.6k.

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