changing characteristics of a river Flashcards
name the three courses of a river?
upper –> middle –> lower
what happens to the gradient from the upper to lower course?
decreases
why does this change happen?
source of river is in the mountain
therefore the gradient has to decrease and become gentler because the mouth of the river is at sea level
what happens to the valley size from the upper to lower course?
increases in size
explain why this change occurs to the valley?
valley increases in size from being V-shaped in upper course to being flat and broad in lower course due to an increase in lateral erosion
what happens to the depth of the river from the upper to lower course?
increases in depth
explain why this change occurs to the depth of the river?
there’s an increase in discharge (from tributaries) therefore the river has more energy so there’s an increase in lateral (mainly) and a bit of vertical erosion and so the river’s capacity is increased
what happens to the velocity of the river from the upper to lower course?
increases
explain why this change occurs to the velocity of the river?
the further down the river course the more tributaries joining the main river therefore there’s more water reaching the river giving the river greater discharge and therefore energy so the rate of flow is faster
also further down the river there’s less friction from big rocks and so the flow is faster
what happens to the width of a river from the upper to lower course?
increases
explain why this change occurs to the width of the river?
more lateral erosion due to greater discharge as river gets nearer mouth (and from tributaries)
what happens to the volume of the river as it goes from the upper to lower course?
increases
explain why the volume changes?
increased discharge due to more tributaries joining the river
