river landforms Flashcards
(29 cards)
give description of v shaped valleys
A valley whose typical cross section is shaped like a ‘v’
what is the formation of the v shaped valleys (how)
As the river cuts down into the landscape in an upland area with vertical erosian, gravity and mass movement roll material down the valley sides to give the valley a ‘v’ shape
what is a gully
smalle v shaped valley
what is the description of a gorge
deep narrow valley with steep sides
how is it formed gorges
formed when a river passes through mountains or is cutting through a band of hard rock
where do rapids pass rapids
shallow fast flowing water in a stream
Wot are waterfalls
steep drop in the bed of a river causing the water in the river to fall vertically
explanation of waterfalls ( formation)
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
alluvial fan description
fan shaped mound of alluvium
explanation of how alluvial fan formed
speed of flow is suddenly greatly reduced. when this happens river is unable to carry much of its load and this alluvium is laid down in a fan shape
where are meander found
middle - lower course
description of meander
bends in river
formed how meander
lateral erosian of the river channel results in the river forming a winding pattern. as water flows down the river, its speed i faster on the outside of the meander causing erosian and slower on the inside of the meander resulting in deposition.
what are ox bow lakes
cut off section of a meander in the river channel which forms a ‘c’ shape.
how is it formed ox bow lakes
loops in a meander eroding the flood plain untill eventually the loop in the meander is left cut off from the main river channel.
what are flood plains
large flat land by either side of a river. this usually becomes wider as the river nears its mouth
how are flood plains formed
when the river overflows its bank, layers of alluvium are laid down.
flood plains are a prime site for agriculture why?
the soil is thick and fertile and the land is flat
what are river terraces
areas of flat land located on either side of the flood plain which are raised above the flood plain.
why might river terraces be a better site for settlement than floodplains
floods can’t reach
how are river terraces formed
the 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
levees wot r they
mounds of alluvium piled up along the river’s edge
how are levees formed
formed by the river depositing the sediment(load such as pebbles, gravel and sand) close to the river channel when the river floods (on the edges). This happens because usually when the warer overflows the river bank, its speed is greatly reduced
why are artificial levees build
prevent flooding
