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KS4
Ho
mew
ork b
oo
klet
River p
roce
sses, features an
d flo
din
gN
ame __
____
____
____
____
___
Class __
____
____
____
____
____
All h
om
ewo
rk mu
st be
com
pleted
by
the d
ue d
ate given
River p
rocesse
sR
iver features
Cau
ses o
f Floo
din
gFlo
od
preven
tion
Erosio
nTran
spo
rtation
De
po
sition
PHYSICAL LANDSCAPES: RIVERS (part 1)Evaporation The sun heats up water. The water turns into a gas which rises up into the atmosphere (air).
Transpiration Trees absorb water through their roots and it evaporates from their leaves as water vapour which rises up into the atmosphere (air).
Condensation As the water in the atmosphere rises, it cools and condenses to form clouds.
Precipitation Water in the cloud falls to the earth’s surface as rain, hail, sleet and snow.Surface run-off When the water runs downhill over the surface of the ground, eventually
entering a river or stream.
Throughflow Water flows downhill through the soil, eventually entering a stream or river
Infiltration When surface water seeps into the soil layer
Drainage Basin The area of land from in which water drains into a specific river.
Watershed The boundary of a drainage basin. It separates one drainage basin from another. It is usually high land.
Source The point where the river begins.
Tributary A stream or small river that joins a larger stream or big river.
Confluence A point where two streams or rivers meet.
Mouth The point where the river meets the sea or ocean.
Long Profile Shows the gradient of a river from its source to mouth.
Cross Profile Shows the shape of the river channel and valley. It is an imaginary ‘slice’ across a river channel/valley at a specific point.
Erosion The wearing away and removal of rock by the river
Weathering The breakdown of rocks or soil, particularly the sides of river valleys because of the day-to-day action of the weather.
Transportation The movement of sediment along the river due to the force of water
Deposition The dropping of sediment when a river slows down and looses energy
River channel The channel that the river actually flows in
River valley The land surrounding the river. It can be narrow or wide.
Contour Line Brown lines on an OS map that join up points of equal height. They allow us to determine slope gradient.
Flash Flood Rapidly rising river levels leading to a fast flood due to heavy rainfall
Storm Hydrograph Shows how river discharge changes after a storm and is used to predict floods
Lag time The time (in hours) between the peak rainfall and peak discharge
Discharge The volume of water in a river channel (measured in cumecs)
The long profile shows the gradient of a river from its source to its mouth. A typical river profile is concave in shape, steep in the upper course and flattening out as you move downstream towards the mouthThe cross profile shows the shape of the river channel and valley. It is an imaginary slice across a river at a specific point. The valley widens as you move downstream
Rivers are split into three courses: • Upper course: steep gradient; vertical erosion so steep V shaped
valleys, waterfalls and gorges; narrow and steep river channel, turbulent shallow water with rapids, Fairly low river discharge
• Middle course: gentle gradient, lateral erosion so wider and deeper river valley and channel, less turbulent faster flow, tributaries join so more discharge added to river. Landforms are meanders, ox-bow lakes and floodplains
• Lower course: very gentle gradient, lateral erosion so very wide open valley floor, widest and deepest river channel, lots of deposition caused by flooding. Landforms are estuaries, floodplain, levees, meanders, ox bow lakes
Erosion is the wearing away and removal of rocks. By the force of the water• Hydraulic Action: The force of the waves hitting the river bed and banks removes material. It is most effective when
there is lots of very fast moving water.• Abrasion: Sediment carried by the river hits the river bed and banks. It acts like sandpaper removing material.• Solution: Chemicals in the water dissolve rocks (e.g. limestone)• Attrition: Stones carried by the river hit into each other, gradually making the rocks smaller and smoother.Weathering is the breakdown of rocks caused by the day-to-day changes in the atmosphere. Also the roots of plants• Freeze-thaw weathering: Water collects in cracks. At night this water freezes and expands. The cracks get larger. In
the day the temperature rises and the ice melts (thaws). The repeated freezing and thawing weakens the rock and breaks apart. Biological weathering: Plants roots break up rocks as they grow and expand in cracks in the rock.
Mass movement is when weathered rocks or soil fall down slopes or when cliffs collapse due to the force of gravity
Deposition takes place where a river does not have enough energy to carry sediment (its load). As a result it is dropped.• Larger rocks are deposited first in the upper course as they require more energy to transport them.• Finer sediment requires less energy to move it. As a result it is deposited further downstream in the middle and
lower course.
Transportation: eroded material is carried downstream by the river because of the energy of flowing water. When in flood a river has lots of energy transports large amounts of material. This is why the water goes brown in colour
Find
the key w
ord
s for th
ese senten
ces
Wh
en th
e water ru
ns d
ow
nh
ill over th
e surface o
f the gro
un
d, even
tually
enterin
g a river or stream
. __________________
Sho
ws th
e gradien
t of a river fro
m its so
urce to
mo
uth
. ________________
The w
earing aw
ay and
remo
val of ro
ck by th
e river. ___________________
Water flo
ws d
ow
nh
ill thro
ugh
the so
il, eventu
ally enterin
g a stream o
r river
___________________
Sho
ws th
e shap
e of th
e river chan
nel an
d valley. It is an
imagin
ary ‘slice’
across a river ch
ann
el/valley at a specific p
oin
t. ___________________
___
The b
reakdo
wn
of ro
cks or so
il, particu
larly the sid
es of river valleys b
ecause
of th
e day-to
-day actio
n o
f the w
eather. ________________
______
______
The m
ovem
ent o
f sedim
ent alo
ng th
e river du
e to th
e force o
f water
__________________
The d
rop
pin
g of sed
imen
t wh
en a river slo
ws d
ow
n an
d lo
oses en
ergy.
__________________
Wh
en su
rface water seep
s into
the so
il layer. ____________________
_____
The lan
d su
rrou
nd
ing th
e river. It can b
e narro
w o
r wid
e _______________
An
swer th
ese qu
estion
s.
1. N
ame th
e three co
urses o
f a river
2. H
ow
do
es the lo
ng p
rofile o
f a river chan
ge as you
mo
ve do
wn
stream
3. D
escribe h
ow
the river cro
ss pro
file chan
ges as you
mo
ve do
wn
stream
4. In
wh
ich co
urse d
o yo
u fin
d vertical ero
sion
becau
se of th
e steep
gradien
t
5. In
wh
ich tw
o co
urses d
o yo
u fin
d lateral ero
sion
becau
se of th
e gentle
gradien
t.
6. N
ame th
ree river features in
each co
urse o
f the river
7. H
ow
man
y types o
f erosio
n are th
ere?
8. D
escribe h
ydrau
lic action
and
abrasio
n
9. W
hich
pro
cess of ero
sion
makes p
ebb
les rou
nd
er and
smo
ther
10
. Describ
e two
types o
f weath
ering
11
. Wh
y do
es transp
ortatio
n h
app
en in
rivers?
12
. Wh
ich typ
e of tran
spo
rtation
mo
ves a) the b
iggest and
b) th
e smallest
material
13
.W
hy d
oes d
epo
sition
hap
pen
in rivers?
14
.W
hy is fin
er sedim
ent fo
un
d fu
rther d
ow
n th
e river?
Wee
k 1 H
om
ewo
rk: Du
e date _
____
____
____
____
_
Use th
e first rivers kno
wled
ge organ
iser to co
mp
lete these tasks
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
In the upper course the relief is steep and the river is small. The river erodes vertically into the landscape. There are many features of erosion
In the middle course the relief is flatter and the river is larger. Both erosion and deposition take place to form river features
In the lower course the relief is very flat and the river is very large. It deposits large amounts of load eroded and transported from upstream
V shaped valleyRiver erodes vertically in the steep relief forming a deep narrow channelSides are weathered and weaken in the cold wet climate.Valley sides collapse into the river by mass movementRiver uses the load to erode a deeper channel by abrasionA V shaped valley is created
Interlocking spursAreas of more resistant rock stick in to the river channelThe river doesn’t have enough energy to erode them so flows around them.The small river zig zags through the landscape
Narrow channelThe river is near its source so has not collected much discharge. The river can only erode a small channel.
WaterfallThe river flows over a band of more resistant (hard) rock on top of less resistant (soft) rock.The river erodes a rock step and a deep plunge pool in to the softer rock. The river undercuts the harder rock which forms an overhang
GorgeThe overhang on the waterfall collapsesover time and the waterfall retreats. After this is repeated a steep sided gorge is left in front of the waterfall
MeandersAs a river flows over flatter relief it finds the easiest route across the land which makes it wander aroundSmall bends begin to formWater on the outside of the bend flows faster so has more energy. It erodes a deeper channel and a river cliffWater on the inside of the bend flows slower so has less energy and therefore deposits a river beach (point bar)Over time the meander grows
Ox bow lakeIn time of flood a river has more energy and may erode a new channel through the neck of a meander. The old meander becomes cut off due to deposition in the slower flow out of the main channelThe old bend is eventually totally blocked off and becomes an ox-bow lake
Flood PlainAs a river meanders on flatter land the constantly changing position of the bends carves out a wide flat valley. The river also regularly floods this area and deposits mud on it. This is the rivers floodplain
Wider channelThe river is now carrying more dischargethat it has drained from many tributaries. It uses this water to carve a wider channel for itself
EstuariesNear its mouth a the fresh water of the river mixes with salt water from the sea. This area is tidal. The river may rise or fall many meters and flow upstream when the tide comes in
Mud flatsLarge areas of deep mud deposited when the river stops flowing when incoming tide and river flow cancel each other out
LeveesRaised banks along the river edge formed as rivers repeatedly flood and deposit larger mud and sand particles first
Very wide and deep channelThe river is carrying a large amount of discharge drained from the whole of its drainage basin so carves a very wide and deep channel for itself
NO FLOOD
• Trees in drainage basin – intercept rainfall = longer lag time.• Gentle rain = more water infiltrated = takes longer to reach river channel• Permeable rock = more water infiltrated = takes longer to reach river.• Dry soils = more water infiltrated = takes longer to reach river channel • Large drainage basins = water has to travel further to reach river = slower
FLOOD • Deforestation – no trees to intercept rainfall = shorter lag time• Intense rain = too fast to infiltrate = more surface runoff = quicker to river• Impermeable rock = rain not infiltrated = more surface runoff = quicker to
river. Impermeable surfaces created when areas are urbanised (concrete).• Steep slopes = quick transfer of water to river channel = short lag time
Up
per co
urse
1.
In w
hich
directio
n (vertical o
r lateral) do
es erosio
n h
app
en in
the u
pp
er cou
rse?
2.
Describ
e an in
terlockin
g spu
r
3.
Explain
the fo
rmatio
n o
f a V sh
aped
valley
4.
In w
hat co
urse o
f the river are w
aterfalls fou
nd
?
5.
Wh
at is the m
ain river p
rocess th
at form
s waterfalls?
6.
Explain
in stages h
ow
river pro
cesses create waterfalls an
d
gorges
Mid
dle co
urse
1.
In w
hat co
urse o
f the river are m
eand
ers form
ed?
2.
Wh
at is a mean
der?
3.
Wh
at two
river pro
cesses form
mean
ders?
4.
Explain
ho
w d
ifferent sp
eeds (velo
city) of w
ater cause a
mean
der to
grow
over tim
e
5.
Wh
at is an o
x-bo
w lake?
6.
Wh
at is a floo
d p
lain?
7.
Ho
w d
o m
eand
ers create a floo
d p
lain?
8.
Ho
w d
oes flo
od
ing an
d d
epo
sition
bu
ild u
p th
e floo
dp
lain?
Low
er cou
rse
1. W
hat is an
estuary?
2.
Ho
w d
o m
ud
flats bu
ild u
p o
n estu
aries?
3.
Wh
at is a levee?
Wee
k 2 H
om
ewo
rk: Du
e date _
____
____
____
____
_
Use th
e secon
d rivers kn
ow
ledge o
rganise
r to co
mp
lete th
ese qu
estio
ns
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
1.
Defin
e river disch
arge?
2.
Wh
at un
it is used
to m
easure river d
ischarge?
3.
Wh
at is a hyd
rograp
h?
4.
Wh
at is peak d
ischarge?
5.
Wh
at is lag time?
6.
Wh
y wo
uld
a river have a sh
orter lag tim
e?
7.
Wh
at hap
pen
s if the rivers p
eak disch
arge gets too
high
?
AB8. W
hich
hyd
rograp
h h
as;
•Th
e sho
rtest lag time
•Th
e high
est peak d
ischarge
•Is m
ost likely to
floo
d after a sto
rm
9.
Wh
at hap
pen
s to th
e soil after p
rolo
nged
rainfall?
10
.H
ow
do
es saturated
soil in
crease disch
arge and
floo
d risk?
11
.H
ow
do
es heavy rain
fall increase d
ischarge an
d flo
od
risk?
12
.H
ow
do
imp
ermeab
le rocks in
crease disch
arge and
floo
d risk?
13
.W
hat is relief?
14
.W
hy d
o rivers in
steep sid
ed valleys o
ften h
ave high
disch
arge
and
floo
d?
Wee
k 3 H
om
ewo
rk: Du
e date _
____
____
____
____
_
Use th
e revision
guid
e page to
com
plete th
ese qu
estion
s
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
RIVER MANAGEMENT AND FLOOD PREVENTION
Dam & Reservoir • Used to control river flow and reduce the risk of flooding. The flow of water can be ‘turned off’ during periods of heavy rainfall. The water is stored in a reservoir so that the river does not flood downstream.
• Effective, long lifespan, used for farming irrigation, drinking water supply, recreation and HEP.• Very expensive, reservoir floods habitats, people have to relocate due to flooding of villages under reservoir.
Channel straightening and Channelisation
• Rivers are straightened by cutting through meanders to create a straight river channel. The river channel and banks may be lined with concrete. This speeds up the flow of water along the river allowing it to get rid of discharge before overflowing and flooding
• Effective as water does not have time to build up, long lifespan.• Expensive, unnatural, damages habitats, result in flooding downstream where water builds up.
EmbankmentS flood walls anddemountable flood walls
A raised riverbank made of earth(levee) or concrete walls lining the river banks. Some walls have demountable panels which can be removed in the summer or in low flow levels to improve the view of the river. They allow the river to channel to hold more water, preventing it overflowing• Effective, long lifespan, can look natural if covered in vegetation• Expensive, if concrete is used it is unnatural and unattractive.
Flood Relief Channel A man-made river channel constructed to divert water in a river channel away from urban areas.• Effective as regulate river discharge (in heavy rain, relief channels are opened)• Very expensive
Hard engineering – using manmade, artificial structures to prevent erosion.More effective at preventing flooding. However more expensive and less natural/environmentally friendly.
Afforestation Planting trees to create a woodland/forest. Trees intercept rainfall preventing it reaching the river• Trees slow down the movement of water into channels (longer lag time) = less likely to flood. Water is stored in trees and so less in river channel. Cheap.• Less effective than hard engineering and not as effective in winter when trees have no leaves
Wetlands Where land next to the river is allowed to flood to store water away from towns and cities• Cheap, easy to maintain, create habitats, stores water so less in river channel. • Means that areas of farmland or parks become flooded so cannot be used
Floodplain Zoning Land is allocated for different uses according to its flood risk. Land closest to the river is used as parkland and land further from rivers is used for housing and industries.• Doesn’t’ stop the flood but reduces overall cost as infrastructure is not destroyed.• Prevents people building on valuable flat land next to the river.
Planning & Preparation Rivers are monitored by the Environment Agency to measure flood risk using weather data, measuring stations and computer models. The Environmental Agency issue alarms if a flood will happen.• People can prepare – sandbags around home, move valuable upstairs, evacuate • Flood still occurs, house prices can drop if deemed ‘at risk’
Soft engineering – using natural, environmentally friendly methods to prevent erosion. It aims to reduce and slow down the transfer of water to the river channel to help prevent flooding.Often cheaper than hard engineering however not as effective at preventing a flood actually happening.
Hard
engin
eering
1.
Wh
at is hard
engin
eering o
n rivers
2.
Ho
w d
oes a d
am sto
p flo
od
ing d
ow
nstream
3.
Describ
e an ad
vantage an
d d
isadvan
tage of d
ams
4.
Wh
at is chan
nelizatio
n?
5.
Ho
w d
oes ch
ann
elization
redu
ce floo
din
g?
6.
Wh
y migh
t chan
nelizatio
n in
crease floo
din
g furth
er
do
wn
stream?
7.
Wh
at is a dem
ou
ntab
le floo
d w
all?
8.
Ho
w d
o flo
od
walls an
d em
ban
kmen
ts redu
ce floo
din
g?
9.
Wh
at is a floo
d relief ch
ann
el?
Soft en
gineerin
g
1.
Wh
at is soft en
gineerin
g on
rivers?
2.
Ho
w d
oes affo
restation
redu
ce floo
din
g do
wn
stream?
3.
Wh
y is afforestatio
n n
ot as effective in
win
ter?
4.
Wh
at is a wetlan
d?
5.
Wh
at is a pro
blem
of u
sing w
etland
s to red
uce flo
od
ing?
6.
Wh
at is floo
dp
lain zo
nin
g?
7.
Ho
w d
oes flo
od
plain
zon
ing red
uce th
e cost o
f floo
din
g?
8.
Wh
y is plan
nin
g and
prep
aration
usefu
l for red
ucin
g the
effects and
cost o
f floo
din
g?
Wee
k 4H
om
ewo
rk: Du
e date _
____
____
____
____
_
Use th
e floo
d d
efences kn
ow
ledge o
rganiser to
com
plete th
ese q
uestio
ns
_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Example: A river valley River Tees
The exam paper may refer to this case study in an exam question as;“Using an example of a river valley you have studied…”
Key idea: The river Tees is a river located in County Durham in North East England. It is often used in Geography text books because it illustrates all of the typical features you would expect to find along a rivers course from it’s source in the steep upper course to its mouth
in the flat lower course. It has a concave river profile which causes typical river processes to occur and river features to form.
Features of a typical river Upper course features: Source in high land, V shaped river valley and interlocking spurs, rapids, waterfalls and gorge.Profile: Steep gradient of highland landscape.River channel: Narrow, shallow, low discharge.Processes: Vertical erosion and transportationMiddle course features: Menders and oxbow lakes, flat floodplain.Profile: Flatter gradient as land flattens out. River channel: Wider, deeper, larger dischargeProcesses: Lateral erosion, transportation and deposition.Lower course features: Large flat flood plain, meanders, levees, estuary, mud flats and river mouth.Profile: Flat land nearer the sea.River channel: Wide, deep, high discharge.Processes: Mostly transportation and deposition.
Typical features of river Tees upper courseSource - At 893 metres above sea level in the Pennine hills in a steep, boggy wet moorland landscape.V shaped valley - the steep gradient of the land causes vertical erosion by the river to erode a deep channel due to gravity. Weathering collapses the valley sides to form a V shape e.g. upstream of high force waterfall.Interlocking spurs - the small river cannot erode more resistant areas of land so flows around them.Narrow river channel – few tributaries have joined and little water has drained from the soils of the drainage basin so discharge is low.High force waterfall – formed because a hard Winstonelayer sits on top of weaker sandstone rocks. The softer rocks below erode more quickly forming a rock step. Hydraulic action erodes a plunge pool and undercuts the hard Winstone causing eventual collapse of the overhang. The waterfall retreats upstream.High force gorge – a steep gorge is formed in front of the waterfall as it retreats slowly upstream.
Typical features of river Tees middle courseWider river channel – more water drains from the land and more tributaries join, increasing discharge.Meanders near Darlington – the gradient of the land is flat so the river wanders laterally. This forms meanders due to differences in velocity causing erosionon the outside and deposition on the inside of the bends. Floodplain – the land is flat so lateral erosion and deposition by meanders, along with deposition of silt during floods has created a wide flat floodplain.
Typical features of river Tees lower courseVery wide river channel - found near Middlesboroughdue to increased discharge from drainage basin.Levees - along the river as flooding deposits material on the floodplain next to the river, forming raised banks.Estuary – wide tidal estuary North of Middlesboroughas the river meets the sea. Mud Flats - Deposition in the slow tidal flow has formed large mud flats. Built on by coastal industry
Example exam question Using an example of a river valley you have studied, to what extent does the riverillustrate the features associated with a river’s course from source to mouth
Example – A river valley – River Tees
The river Tees is located in __________ ___________ in __________ __________ England. It has all the typical features you would expect to find along a rivers ___________ from its source in the steep ___________ course to its mouth in the flat ___________ course. It has a _____________ river profile. concave profile which means __________ at the top and ___________ nearer the bottom.
Features of a typical river
Upper course featuresTypical features include _________ , ___________ and ____________The gradient of the land is _____________The river channel is _________ with low ________Processes include ________ erosion and ________
Middle course featuresTypical features include ___________ , ________ lakes and a flat _____________The gradient of the land is ______The river channel is _______ with larger ________Processes include ________ erosion ________and ________ .
Lower course featuresTypical features include large flat _________ , _________ , _________ and ____________The gradient of the land is _____________The river channel is _______ with high _________Processes include ____________ and _________ .
Features of the River Tees upper course
The source of the river in in the __________ hills.It is a boggy ____________ landscape.
_______ shaped valleys are found caused by _______ erosion in the _________ gradient. A deep channel is eroded and _________ collapses the valley sides.
Areas of land that stick out because the river can’t erode them are called ___________ spurs.
Small streams joining the main one are called _________ . Few have joined so far and little water has drained into the river so the __________ is low.
The famous waterfall is called ________ force.This formed because hard ___________ sits on top of soft __________ so a rock step forms. The deep pool eroded at the bottom of the step is called the _________ pool.The Winstone collapses because it becomes _______ .The waterfall ________ upstream leaving a _______ .
Features of the River Tees middle and lower course
Middle courseThe river is wider because more _________ join, increasing the rivers discharge.
Meanders are found near the town of ____________ .Meanders form because the river wanders ________ .The river is faster on the outside of the bend so ________ occurs. The river is slower on the inside so _________ occurs.
Floodplains are formed due to erosion and deposition by ___________ as they move across the land, and the build up of ________ during river floods.
Lower courseThe river is very wide near the city of ____________ .Raised banks along the river edge caused by material being deposited during floods are called ________ .The tidal area as the river meets the sea is called an ___________ .________ flats are formed here due to deposition.
Week 5 Homework: Date Due ________________________________
ExampleFloodingBoscastle
The exam paper may refer to this case study in an exam question as;“Using an example of a flood management scheme you have studied…”
Key idea: Boscastle is a pretty, rural village in South-West England. The main economy is tourism. Flooding in 2004 flood caused huge destruction and devastated the tourist industry. £4.6m was spent to improve its flood defences. Mostly Hard Engineering strategies were
used. The new defences are economically and socially sustainable because they protect local peoples homes and businesses from flooding and blend in so tourism is not affected. However, there was some environmental damage to river habitats.
What caused the flood. Natural factors that increased the flood risk • 200mm of rain fell over Ottersham Moor; east
of Boscastle, within 4 hours, saturating the land and causing rapid surface run-off in to the river.
• The land was already saturated from previous rainfall so water couldn’t infiltrate so there was more surface run-off to the river
• Boscastle is the confluence (joining point) of the River Jordan and Valency increasing river discharge.
• Steep and narrow valley sides caused rapid surface run-off to fill the river.
• The tide came in blocking the flow of the river.Human factors that increased the flood riskThe village is built on the flood plain right next to the river meaning it floods easily.Impermeable building surfaces also increase surface run-off in to the river, increasing discharge.
The Management StrategyChannelisation. The River Valency was made deeper & wider to contain more discharge.Car Park. This was raised in height so that cars would be at less risk of a flood.Bridges. The upper and lower bridges are replaced by stronger wider bridges that are less likely to get blocked by trees and debris.New Culverts. The River Jordan now flows through wider stone culverts that go under the main road before joining the River Valency so more discharge can flow through.Afforestation. Unstable trees were cleared & new ones planted near the river meaning less chance of culverts being blocked by trees.Prediction. River Level Gauges measure the discharge of the River Valency & data is shared with the Environment Agency to help forecast future flood events.
Social, Economic & Environmental EffectsSocial. Community was ‘torn apart’. People had to rent properties outside of the village. Children had to go to different schools. Sewage pipes burst and so people weren’t allowed into their homes due to Health & Safety concerns.Economic. 25 businesses destroyed. £20million’s worth of insurance claims. 4 foot-bridges & 50 cars, pavements & gardens washed away. Lost tourist income for many months, so 20 businesses closed. Environmental. Trees were uprooted. Wildlife & habitats destroyed. Fuel & Oil leakages in Harbour.
How sustainable are the defences?Economic – Expensive (£4.6m) but effective because defences prevented flooding in 2007, saving millions.Social - Protect properties and livelihoods e.g. tourismEnvironmental – built to blend in using natural stone but channelization damages river habitats, effecting local biodiversity.
Example exam question Using an example of a flood management scheme you have studied, to what extent does the scheme benefit both the local people and the environment. [6 marks]
Example – Boscastle – Flooding and flood defences
Boscastle is in _______ ________ England. The main economy in Boscastle is _________ The year the flooding occurred was _________ .
The cost of improving the flood defences was £ __________ million. The defences are _____________ sustainable because they protect homes and _____________ sustainable because they protect businesses and jobs. However there was some ________________ damage toriver ____________ .
What caused the floodNatural factors
_____________ mm of rain fell in 4 hours
Rainfall ___________ the land so water couldn’t infiltrate into the soil. Rapid __________ run-off filled the river quickly.
Two rivers join and flow through Boscastle. The river ____________ and the river ___________ This increases river ___________ .
Boscastle is in a steep and narrow _________ causing rapid ___________ run off.
Human factors
The village is built on the _________plain next to the river so is easily flooded.
___________ surfaces increase surface run-off to the river as water cannot infiltrate the ground.
The Management strategy
Making the river deeper and wider is called _________________ . This allows the river to hold more ______________ stopping it overflowing.
The _______ park was raised above ________ levels. This means cars are less at risk from floods.
Bridges were __________ so they wouldn’t become __________ by debris.
Wider stone ______________ flow under roads so more ______________ can flow through.
Unstable trees were ____________ and new ones _____________ so that they are less likely to fall down and block culverts.
River level ___________ measure _____________ to help forecast future _____________ . This is known as ________________ .
Effects of the flood
Many people had to ___________ properties outside the village.
___________ pipes burst causing health and safety concerns, preventing people returning home.
__________ businesses were destroyed.
£ ____ million worth of insurance claims were made.
__________ cars were washed away.
The __________ industry affected for many months.
The defences are effective because they prevented further flooding in ________ , protecting ___________ and livelihoods e.g. ___________ .
They are built using natural __________ to blend in.
Channelisation does however damage river _______ .
Week 6 homework: Due date ______________________
‘River flo
od
ing is an
entirely n
atural even
t’To
wh
at extent d
o yo
u agree w
ith th
is statemen
t?U
se an exam
ple o
f a recent flo
od
to su
pp
ort yo
ur an
swer [6
marks]
The B
oscastle
floo
d w
as caused
to a ____________ exten
t by n
atural cau
ses bu
t in
creased b
y hu
man
factors.
The m
ain n
atural cau
se was ________________
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___Th
is caused
floo
din
g becau
se __________________
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Also
oth
er natu
ral causes in
clud
ed ________________
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is caused
floo
din
g becau
se __________________
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Ho
wever th
ere were also
hu
man
factors th
at increased
the flo
od
ing
A h
um
an facto
r was _______________
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___Th
is increased
floo
din
g becau
se ___________________
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Explain
ho
w h
ard en
gineerin
g has b
een u
sed to
redu
ce the fu
ture risk o
f floo
din
g in
Bo
scastle[4
marks]
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Wee
k 7 H
om
ewo
rk: Du
e date __
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