Which waves builds up the beach?
Which wave has a stronger backwash?
Which wave has low wave height?
Constructive waves usually happen on gentle
or steep slope beaches? Why?
Destructive waves are ‘spilling’ or
Waves + the coast
Not only do waves erode the coast, they
also transport and deposit the material
that they erode to different places
Southsea beach may have been eroded and
transported there from France
How do waves transport material?
The sea transports massive amounts of rockThe sea transports massive amounts of rock
material around every daymaterial around every day
Some bits are as small as sand, other bitsSome bits are as small as sand, other bits
are big pebbles or even bouldersare big pebbles or even boulders
Coasts are not just eroded, they are also built
up by deposition – this is when eroded material is
dropped off and builds up over time
This creates beaches
Deposition happens when waves are constructive
(so the swash is bigger than backwash so
material gets moved up on to the beach).
Material is moved by the sea and can travel miles
Longshore drift (LSD) is the process where
waves transport eroded material along a
beach and deposit it down coast
Make your own copy of
the LSD diagram, with
Q)What controls the
direction of movement
along a beach?
Q)What direction does
most material move on
the south coast of
Why do we get
How is material
Q) Why is LSD sometimes a problem?
Q) What do we do to stop LSD?
Beaches, spits, bars and tombolos are
created by deposition and transportation
Beaches are basically eroded material that
has been transported from somewhere else
Write your own summary (just a few
sentences) to explain:
Extension: Answer Q1,3
Find some pictures of beaches, bars, spits and tombolos
to stick in to your book.
Put your target grade on to your tracker
If you want to set yourself a higher target
you may, these are the minimum grades the
school expects you to get based on last
year’s data and so far this year
When material is dropped off, deposited,
when the sea no longer has enough energy
to transport it
The transport of material along the beach
by the sea in the direction of the prevailing
BeachesBeaches develop when the supply of sediment exceeds any
sediment lost through backwash and longshore drift.
Beaches are usually distinguished as either …
Shingle beaches are free draining so there is little backwash of material
to sea. As a consequence, they are usually steeper.
Some features of a
shingle beach ..
... The largest material
is found furthest from
You get ridges across
the beach called
have a more
Wet sand compacts, so water doesn’t drain through it.
This means that backwash, and the material it is carrying,
is able to return to the sea.
Sand is smoother
than shingle.... so
there is less friction
to prevent the
back down the
These get colonised by grasses and become ecosystems
As on-shore winds blow across dry beach sand, it carries
material inland to form sand dunessand dunes
Spits and BarsSpits and Bars
Where there is a change in the coastline e.g. a headland or
an estuary mouth, longshore drift may continue to deposit
sediments into the sea forming a spit.
Spurn HeadSpurn Head at the mouth of the Humber
estuary is a fine example of a spit.
Local currents and changes in wind direction may curve
the end of the spit landwards creating a hooked tip.
The presence of the estuary discharging river water into
the sea prevents the spit from developing into a bar.
Such a feature is known as a recurved spitrecurved spit
If a spit joins on to one part of the mainland to another it is
called a barbar.
For example, there is a bar at Slapton SandsSlapton Sands in Devon.
Where a spit
mainland to an
island a tombolo
may be created .
The longest and best known tombolo in Britain is
Chesil BeachChesil Beach.
Have a go at the exam paper
Some of you have tried it before but have another
go with more knowledge
Now mark it against the model answer sheet and
give yourself a grade
12-13 = A 7-8 = D
10-12 = B 6-7 = E
8-10 = C 5-6 = F
less than 4 = U