Rivers

Question 1

describe the upper courses characteristics

Answer 1

v-shaped valley due to lots of vertical erosion
shallow and steep
slower velocity due to a more turbulent flow
sometimes waterfalls
low discharge

Question 2

describe the middle courses characteristics

Answer 2

wider as therers lots more lateral erosion
more meanders and therfore oxbow lakes
its deeper and quicker flowing
waterfalls and gorges also can occur
surrounded by a flood plain

Question 3

describe the lower courses characteristics

Answer 3

very flat
wide due to lots of vertical erosion from high energy water
more deposition
natural levees are also commonly found
high discharge

Question 4

doe the size of the bedload increase or decrease going down the rivers course?

Answer 4

decrease as theres been more erosion

Question 5

what does releif mean?

Answer 5

the shape of the land

Question 6

what is interception of water?

Answer 6

when plants get in the way of the flow of water towards a river

Question 7

what is infiltration of water?

Answer 7

when water infiltrates the soil

Question 8

what is the lag time of a river?

Answer 8

the time difference between peak rainfall and peak discharge

its best if this time is longer

Question 9

what are the falling and rising limbs?

Answer 9

when discharge is decreasing or increasing

Question 10

what might cause a flashy hydrograph?

Answer 10

having….
heavy rainfall
steep sides
few trees and plants
impermeable rock
lots of tributaries
urbanised area

Question 11

what might cause a slow response hydrograph?

Answer 11

lots of trees
permeable rock
not as many tributaries
deurbanised area

Question 12

how are waterfalls created?

Answer 12

River flows over horizontal layers of hard and soft rock, softer rock underneath is eroded away quicker than the harder rock on top due to differental erosion and keeps being eroded away by hydraulic action and abrasion untill an overhang and plunge poolk are created. The overhang then collapses into the plunge pool causing the waterfall to retreat backwards. THis also means a steep sided gorge is formed downstream.

Question 13

How are interlocking spurs formed?

Answer 13

The river tries to find the path of least resistance down the hill so will maneuvour around harder rock obstacles creating interlocking spurs

Question 14

how are flood plains created?

Answer 14

when a river overflows its banks and deposits its sediment on the area leaving very flat, fertile land on either side

Question 15

how are natural levees formed?

Answer 15

When a river floods it loses energy meaning it must deposit its heaviest material on the banks. When the water receds this sediment is left and the process repeats creating raised embankments known as levees.

Question 16

How are meanders created?

Answer 16

Water flows fastest on the outside of the slight meander this means there will be more erosion on this side and slower in the inside. This menas the outside has a steep cliff that is being constantly eroded and the inside is left with a slip off slope as the slow water loses energy and deposits its load there.

Question 17

how are oxbow lakes formed?

Answer 17

Water flows quicker on the outside of a meander than the inside meaning the outdside is constantly being eroded away. The neck of the meander therfore keeps getting narrower untill it is completely cut off from the rest of the river. The river now takes on a straighter path and the ox bow lake eventually dries up leaving an ox bow scar

Question 18

How are deltas formed?

Answer 18

when sediment is deposited by th river when it meets the sea where is has no energy. Sediment fills up the estuary of the river forming an island or new land.

Question 19

What are the factors affecting the hydrograph of a river?

Why?

Answer 19

Rock type-if rock is impermeable means more surface run off (quickest route)
Releif- steeper means quicker to get to river
Precitpitation type-more precipitation means ground becomes too saturated and no more water can infiltrate so surface run off
Urbanisation-more drains which bring water quickly to the river
deforestation- less interception
Farming- removes vegetation and creates impermeable surfaces

Question 20

give some examples of hard engineering strategies?

Answer 20

dams and reservoirs- blocks the river so that its flow can be controlled and released
channel straigtening- creates a straighter faster flowing channel so water can pass through quickly
enbankments- makes river channel deeper so river levels can rise higher without flooding
flood releif channels- diverts excess water away from vulnerable areas

Question 21

give some examples of soft engineering strategies?

Answer 21

flood and warning preparation- people are warned before a flood to give time to prepare
floodplain zonning-different areas are given different flood risk and they wont build on high flood risk areas
afforestation- planting trees more interception
river restoration-refering ti a river returning to its natural course

Question 22

What is a drainage basin?

Answer 22

an area of land drained by a river and its tributaries

Question 23

what is the confluence?

Answer 23

the point where two rivers meet

Question 24

what is a tributary?

Answer 24

a smaller river that flows into a larger one

Question 25

what is the source of a river?

Answer 25

the point where a river starts

Question 26

why is it bad if countryside is built on?

Answer 26

ground can not act as a sponge so water is channeled through drains back into the river causing flooding

Question 27

what is percolation?

Answer 27

when water goes into the rocks