rivers

Question 1

drainage basin

Answer 1

an area drained by a river and its tributaries.

Question 2

Lateral erosion

Answer 2

sideways erosion

Question 3

Evaporation

Answer 3

water heated turning from a liquid to a gas (water vapour)

Question 4

Erosion

Answer 4

the wearing away of the land

Question 5

abrasion

Answer 5

material carried by the river smashes against the banks wearing them away

Question 6

attrition

Answer 6

rocks smashing into each other gradually become smaller and rounder

Question 7

hydraulic action

Answer 7

the force of the water and/or forces air into cracks making them wider

Question 8

solution

Answer 8

where water has a chemical reaction with the rock and dissolves it

Question 9

suspension

Answer 9

lighter material is carried in the river.

Question 10

solution

Answer 10

dissolved material transported

Question 11

saltation

Answer 11

heavier material is bounced along the bed of the river.

Question 12

traction

Answer 12

the heaviest material is rolled along the bed of the river.

Question 13

deposition

Answer 13

when material is dropped by the river

take place where the velocity of the river slows down for example on the inside of a meander, at the mouth where the river meets the sea, or on the floodplain when it overflows.

Question 14

name the 3 processes

Answer 14

erosion, transportation and deposition

Question 15

name the 5 landforms

Answer 15

v-shaped valleys, waterfalls, meanders, oxbow lakes, floodplain

Question 16

how does the river change from upper to lower course

Answer 16

River becomes wider
Discharge increases
Velocity increases
Gradient decreases

Question 17

why does a river change from upper to lower course

Answer 17

River becomes wider - as a river reaches its lower course lateral erosion becomes more common, as gradient decreases, widening the river.
Discharge increases - as more tributaries join the river amount of water increases.
Velocity increases - as bedload has become smaller and banks and bed smoother friction decreases therefore increasing velocity.
Gradient decreases - due to meander migration widening the valley floor

Question 18

Interlocking spurs

Answer 18

The river at its source is small and has limited energy. It flows naturally from side to side around ridges of more resistant rock creating spurs.

Question 19

v-shaped valley

Answer 19

vertical erosion takes place deepening the channel whilst weathering attacks the slopes, weakening the rock until mass movement moves the material downslope.

Question 20

waterfall process

Answer 20

Hard, more resistant rock overlays softer less resistant rock. Soft rock is eroded more rapidly through hydraulic action/corrasion undercutting the hard rock creating an overhang. The force of the water creates a plunge pool. The hard rock collapses under its own weight and the process repeats, retreating upstream to create a gorge.

Question 21

process of meanders/oxbow lakes

Answer 21

Water flows fastest on the outside of a meander eroding the banks, creating a river cliff. On the inside of the bend where the river is flowing slower deposition takes place creating a slip-off slope. As erosion continues at the neck of the meander it becomes narrower. Normally in flood conditions the force of the water breaks through creating a new channel. The old part of the river is cut off as deposition now takes place along the banks of the river, creating an oxbow lake.

Question 22

flood plain

Answer 22

the floodplain is a wide flat area of land either side of the river. In its lower course meander migration takes place. This occurs due to lateral erosion eroding the outside of the bend and deposition on the inside moving the meander across the valley floor, widening and flattening it.

Question 23

what were the physical causes of the Boscastle flood

Answer 23

Intense rainfall, 185mm in 5 hours, did not allow time for water to infiltrate therefore overland flow increased.
Large amount of rainfall earlier in the week and an input of 3 million tonnes of water meant ground was saturated and could hold no more water.
Confluence of 3 rivers, Valency, Jordan and Paradise drained a small drainage basin of just 40Km2.
Geology - impermeable sandstone did not allow water to infiltrate and therefore overland flow increased.
Steep valley sides reduced infiltration and thin soils couldn’t hold much water

Question 24

what were the human causes of the boscastle flood

Answer 24

Narrow bridges became blocked with trees diverting water into the streets.
Deforestation results in fewer trees to intercept and store water . Therefore more water gets to the river channel.
Urbanisation results in water flowing rapidly into drains over impermeable surfaces. The water gets to the river channel too quickly.

Question 25

when was the boscastle flood

Answer 25

august 2004

Question 26

what was the result of the boscastle flood

Answer 26

Water rushed down streets at 40mph as a 10ft wall of water ripping up roads and destroying both bridges 80 cars in the car park were swept away in minutes. 6 properties were destroyed outright. Most others needed £15,000-£30,000 repairs Loss of trading amounted to £15m Bed of the river Jordan was 10 feet higher Most houses had 2 feet deposit of mud Most shops stayed shut for rest of the season Trade in tourism reduced. Value of homes permanently reduced - some by half.

Question 27

how was flooding prevented on the river severn in shrewsbury

Answer 27

Demountable barrier system – 1.5m to 3m tall, offers protection from 1 in 100 year flood Adding two new pumping stations to reduce water backing up in drains.£3.5 million scheme - 1 in a 100 year chance Flood embankments, located in a conservation area, so made sure they blended into the surrounding area. £2.4 million scheme, reduce the level of flood risk to a 1 in 100 Clywedog dam and reservoir, in the upper course of the Severn. Gives some protection immediately downstream but little benefit to Shrewsbury Natural flood meadows (washlands) exist upstream of Shrewsbury and provide some protection Levees constructed to provide protection for low lying agricultural land. Reduce risk of flooding to 1 in 10 or 20 chance in a year

Question 28

advantages of hard engineering

Answer 28

Very effective Strong and durable

Question 29

disadvantages of hard engineering

Answer 29

Expensive Visually unattractive

Question 30

advantages of soft engineering

Answer 30

Relatively cheap Blends in with the natural environment

Question 31

disadvantages of soft engineering

Answer 31

May not be as long lasting or as strong Can lead to conflict e.g. allowing certain places to flood

Question 32

land use zoning

Answer 32

areas in a city are set aside for certain functions to reduce the impact of flooding

Question 33

examples of land use zoning

Answer 33

Areas close to a river are set aside for sports and recreational activities. Hospitals occupy higher land away from the risk e.g. JR Residential areas tend to be on higher ground than industries due to the risk of life.

Question 34

what is the regime

Answer 34

the pattern of a river’s flow over a period of time, usually a year.

Question 35

what factors is the regime dependent on

Answer 35

First is the amount of precipitation during the year, more in the winter will lead to an increase in flow during that time. Geology will impact, with impermeable leading to fluctuating regime. Forest - loss of leaves in the winter will lead to more water reaching the river

Question 36

conflicting views in shrewsbury

Answer 36

Over spoiling the historical beauty of the town How useful actual flood protection will be The impact on the environment versus keeping people safe Justification of the cost of the protection The disturbance caused to locals whilst construction takes place Places being allowed to flood e.g. farmers fields Impact on places further downstream

Question 37

Thames Estuary

Answer 37

Conflicting views over how long the Thames Barrier will be useful for - hard to predict future changes and how they might impact. Flood walls being used are protecting properties but others feel they funnel the water towards London Managed realignment - landowners do not want farmland flooded but does soak up pollutants and provides a habitat,as well as protecting places further upstream Building houses in the Thames Gateway - prime building land but increasing the risk of flooding