hard and soft engineering1

7/21/2019 Hard and Soft Engineering1

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Coastal Management

Lesson Objective:

Understand why methods of engineering to protect thecoast have advantages and disadvantages



MANAGING THE COASTLINE

Hundreds of thousands

of tonnes of chalk fell

500ft to the beach on

Sunday morning, in what

is thought to have been

the biggest sudden loss

of coastline in Britain

in living memory.”

“Beach hit by 200 tonne cliff

collapse”

“Cliff collapse

in Egypt leaves

24 dead”

“Beach closes after cliff

collapse”

“HolbeckHall Hotel

crashes

into the

sea”

“Myhouse is

only

worth



Coasts : Coastal Protection / Hard and Soft Engineering Strategies

Possible Questions :

Why might cet!in co!st!l

"otection metho#s be selecte#

inste!# o$ othes%

Wh!t is the #i$$eence bet&een

H!# !n# So$t co!st!l "otection

techni'ues%

There are many different ways to reduce the rate of

coastal erosion. Some are more expensive than

others, some last longer, some are less of an eye-sore ..etc. There are 2 main categories of coastal

protection:

HA! "ngineering Strategies : #uilding or creating

something which will interfere with coastal processes $ usually to reduce the power of

%rea&ing waves against cliffs.

S'(T "ngineering Strategies : )or&ing with the

natural processes of sea and sand in a moreenvironmentally sustaina%le way. Using the natural

processes to %ring a%out an intended effect.

!



HA() ENGINEE(ING



Ho& #o goynes &o*%

Groynes trap the sand which is carried along thecoast by longshore drift.

The sand acts as a natural protection against the

force of the waves. The waves break onto the



Goynes

" #hese are b$ilt at right angles to the coastline%

" #hey aim to slow down longshore drift and trap sediment%

" #hey can be made of timber& concrete or roc'%

" (ood groynes are aro$nd )*&+++ each%

" ,oc' groynes cost aro$nd )-++&+++ each%

A#+!nt!ges:

" More beach material to dissipate wave energy which slows down

cliff erosion%

" Cheap in comparison to other hard engineering methods)is!#+!nt!ges:

" Beaches f$rther along the coast are starved of beach material d$e

to their affect on long shore drift%



Wh!t !e the #is!#+!nt!ges o$ goynes%

n 1""1 a rock revet#ent

and two rock groynes werebuilt. $and accu#ulated andhalted erosion.

$outh of Mappleton% therate of erosion has increasedsigni&cantly.

Material that usually #oves

south via longshore drift isbeco#ing trapped within thegroynes.

'ow there is no beach torotect the clis ( the sea

Mappleton is locatedon the HoldernessCoastline.



Se! W!lls" .ea walls aim to prevent erosion by providing a barrier%

" #hey reflect the seas energy%

" #he walls are placed parallel to the shore%

" #hey are $s$ally e/pensive and can cost $p to )*+++ per s0$are metre%

1dvantages:

" 2rovide e/cellent defence where wave energy is high" #hey reass$re the p$blic

" #hey have a long life span%

)is!#+!nt!ges:

" 3/pensive

" Ugly4 can p$t off to$rists" #hey can ma'e it harder to access the beach

" ,ec$rved sea walls ca$se greater erosion at the base of the wall



What problems do sea wallscreate?

ight a sea wall cause more coastal ero



(i" !", (oc* Amou

" #hese are often large bo$lders placed along the base ofa cliff to absorb energy from waves%

" #hey cost abo$t )5+++ per metre

A#+!nt!ges:

Cheap and efficient

)is!#+!nt!ges:

" Ugly

" 6angero$s access to beach

" Costs increase when roc' is imported



(e+etments

" #raditionally these have been wooden slatted barriersconstr$cted towards the rear of beaches to protect thebase of cliffs% 3nergy from waves is dissipated by thembrea'ing against the revetments%

" Cost: )-+++ per metre

A#+!nt!ges:" Less beach material is eroded compared to a sea wall

" Cheaper and less intr$sive than a sea wall

)is!#+!nt!ges:

" .hort life span

" Uns$itable where wave energy is high



Offshore reef

" 3normo$s concrete and nat$ral bloc's are s$n' offshore to alter the

wave direction

" Cost )&8*+ per metre

A#+!nt!ges" #he waves brea' f$rther offshore so red$ce erosive power

" #he allow the b$ild $p of sand

)is!#+!nt!ges" May be red$ced by heavy storms

" 6iffic$lt to install



SO-T ENGINEE(ING



.e!ch (e"lenishment

Beach replenishment is also known as

beach nourish#ent.

)each nourish#ent is the process of du#ping orpu#ping sand fro# elsewhere onto an eroding

shoreline to create a new beach or to widen thee*isting beach.

Beach nourishment does not stop erosion% it

si#ply gives the erosional forces +usually waves,so#ething else to -chew on- for awhile.

The waves erode the nourished sand instead ofdestroying houses% roads or parking lots. )ecausenourish#ent doesnt stop erosion% nourish#ent #ust



M!n!ge# ete!t

" #his is when areas of coast are allowed to erode%" #his is $s$ally in areas where the land is of low val$e%" Cost: depends on amo$nt of compensation that needs to

be paid to people affected by erosion%

A#+!nt!ges:" Managed retreat retains the nat$ral balance of the

coastal system%" 3roded material enco$rages the development of

beaches and salt marshes%

)is!#+!nt!ges:" 2eople lose their livelihood e%g% farmers% #hese people

will need to be compensated%



Cliff regrading

Ma'ing the cliff face longer so that it is less steep

A#+!nt!ges:

" Cheap

" ;at$ral4 will enco$rage wildlife bac' into the area

)is!#+!nt!ges:

" ;ot effective on its own4 need other defences at thebase of the cliff

" .ome homes on the cliff may need to be demolished



(hat may infl$ence decision

*hoosing which methods of coastal protection is most appropriate for an area of

coastline may ta&e into account the following:

+ COST : concrete sea wall is expensive. )ood revetments are cheaper

+ LIFETIME : roc& groynes may last decades. #each re%uilding will have to %e

carried out every few months

+ ENVIRONMENTAL IMPACT : offshore reefs will not affect the loo& of the %each %ut

concrete will loo& awful and put tourists off using the coastline

+ SUSTAINABILITY : using hardwood from tropical rainforests for tim%er groynes is

not sustaina%le $ they will deteriorate and need replacing faster than newhardwood trees grow. #each re%uilding is sustaina%le as you are moving sand from

where it has %een deposited, to where it has %een eroded from.

h li b



How can the coastline beprotected?Hard engineering techni/ues ai# to stop coastalprocesses fro# occurring. Soft engineering #ethods tryto work with nature to protect the coast.

M t h th f ll i t t t t



Match the following statements to

yo$r pict$res of hard and soft

engineering wor'sheet%

(rite in pencil if yo$ are $ns$re<

I$ you $inish/ use "!ge 01,02 o$ the te3tboo* to!## moe #et!il4

Ho& #oes it &o*% A#+!nt!ges )is!#+!nt!ges



Ho& #oes it &o*% A#+!nt!ges )is!#+!nt!ges

(ooden str$ct$res brea' the forceof the waves and trap beachmaterial behind them%

M$ch cheaper than a sea wall%3ffective at brea'ing the force of thewaves%

Less d$rable than a sea wall = mayneed replacing 0$ic'er%6oes not give total protection to thebase of the cliff%Cost appro/ )+++ per metre

Large bo$lders on the beach =lesson the force of the waves byabsorbing the wave energy withinthe gaps between the roc's%

,elatively cheap%Use nat$ral material>roc's

3nvironmentally $gly % Can beremoved by the waves d$e to thewashing away of sand and shinglebeneath%

B$ild $p the beach by replenishingbeach material& partic$larly at thebase of str$ct$res to provide a?nat$ral@ sol$tion to absorbing waveenergy%

2rovides a nat$ral sol$tion%;at$ral loo'ing = meaning it isdiffic$lt to tell management is ta'ingplace%

Can be e/pensive to 'eeptransporting large amo$nt of sand =sediment moved by longshore drfitso will need fre0$ent replenishment$nless $sed with other defences%

Concrete wall& c$rved $nder side todeflect the power of the waves%

#hey reflect rather than absorbwave energy%Most effective means of preventingerosion%

Most e/pensive 9$p to )-%*million>'m%6eflected waves often sco$r thebase& $ndermining it = it maycollapse in the f$t$re%

Cages of bo$lders b$ilt into the cliffface = small roc's help to absorbthe wave energy%

3ffective where severe erosion andcheaper than sea walls%

3nvironmentally $gly 9$s$ally $sedin large n$mbersCost is appro/ )5*+ per metre%

(ooden or in some cases steelstr$ct$res that stop longshore driftand b$ild $p> anchor the beach&

protecting the base of a cliff%

.tops longshore drift enco$ragingthe b$ild $p of the beach andeffectively red$cing erosion%

Can increase erosion f$rther downthe coast by stopping longshoredrift and starving areas f$rther

down the coast of sediment% Costappro/ )*4A+++ each%



Lin's to olderness case st$dy

" http:>>www%yo$t$be%com>watchvD1E8eO

C43rO+

http://www.youtube.com/watch?v=AG9eOC-ErO0






ConsiderF%

% (hy are settlements defended while

agric$lt$ral land is left to the actions of the

sea

-% .ome people are for coastal protection

schemes and others are against% 3/plain

these different opinions%



2ast e/am 0$estion

hard and soft engineering1

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