CLIFF!

Cliffs are formed when water flows through a steep rock surface. Hydraulic action and abrasion are the main cause of erosion of the rocks by undercutting to form a notch. As undercutting continues, it will deepen to form a cave, which might then deepen further and cause the overhanging cave to collapse. As overhanging cave collapse, the debris form will accumulate at the base and will either be washed away by the sea water or carried away by the crashing waves. As this continues, a cliff is formed and a platform at the bottom of the cliff will also form known as the wave-cut platform.

COAST! (:

Coast is the part that merges and adjoins with the sea.
Wave is the movement of the water surface of the sea and is driven by wind.
The size of waves affected by 3 factors:
1) Fetch: The longer the fetch, bigger the waves formed
2) Wind movement: Bigger wind movement, bigger the waves
3) Wind duration: The long the duration of wind, the larger the waves.
-> Water that flows in deep water will lose energy
-> Water that flows near to shore will slow down due to friction
-> Friction will cause waves to rise and bend
-> As it continues bending, it will bend and form foams.

Constructive Wave Destructive Wave
Long wave length Short wavelength
Short wave height Long wavelength
wave frequency of 6-8 wave frequency of 10-14
spilling beaker plunging beaker
Happens in sheltered and gentle coast Happens in open and steep coast
Erosion is most prominent Deposition most prominent

Tides are the daily alternate rising and falling of sea level due to gravitational pull on the moon, and to a certain extent, the sun.
It has an impact on the coast: During high tide, erosion of the coast occurs and on low tide, it will transport large part of the coast away.

Currents are large-scale, persistent movements of the water, largely driven by prevailing wind.
They are responsible for shaping the coast and thus is able to transport a huge area of coast over a long distance in a short period of time.
Longshore currents are currents that are formed when waves approach the coast at an oblique angle, and is parallel to the coast.

Coastal Erosion is affected by 4 factors:
-> Type of wave: Usually destructive; more energy for erosion
-> Minerals and composition of rocks; Those with more lines of weaknesses will get eroded
first as compared to lesser ones. Softer rocks will get eroded faster than hard rocks; Those
with dissolve minerals will erode away faster ; usually in open and steep coast.

Coastal Deposition is affected by 3 factors:
Gradient: Gentle gradient
Sediments: Speed of coast is slow and a lot of sediments there and so it will settle down on
bed of coast and get deposited.
Position of coast: gentle and sheltered coast

Coastal Transportation: By Longshore drift
-> Waves that approach the coast at an obique angle and are parallel to coast
-> Sediments are transported to the shore by swash
-> Sediments will then be pulled back by backwash that moves perpendicular to the shore.

Let's Compare!

Hmm.. Lets all compare between the management of rivers and coast.

Rivers:
River channelisation rivers to the different methods and strategies to manage the river so as to prevent it from reaching flood height.
1) River alignment
- Refers to the altering of the river course so as to reduce the chances of erosion from taking
place.
- Can be done by removing large boulders from river channel and also deepening and widening
of the river through dredging.
- Examples where this is carried out is in Kallang and Singapore River
2) River re-sectioning
- Refers to the re-sectioning of a river which can be done by shortening the river
- Example of it is the Mississippi River that has been shortened by 240km to reduce the threat
of flooding
3) Vegetable Planting and Clearing
- By planting vegetable, it is to slow down speed of flow by reducing surface runoff to the
river channel and this has negative impacts which are adding weight to bank stress which
might eventually lead to the collapse of the bank and also debris from plants to increase
rate if erosion in different parts of the river.
- By clearing vegetable, it is to increase rate of flow as there will be more surface runoff.
This is to decrease the chances of flooding to occur. However, it is a viable option.
4) Bank Protection
- Building banks, levees and embankments to protect the banks and prevent it from collapsing
during heavy downpour.

Coast:
It is important to manage coast as it will ensure that development is properly planned and managed to prevent damage of coast by erosion.

Hard engineering approach that involves building of physical structures do as to defend against erosive power of waves.

1) Seawall
- Build along coast and is made of either concrete, wood or rock
- They help to absorb high energy waves before they erode away loose beach materials
Negative Impact:
It is unable to prevent powerful backwash from washing away beach materials beneathe the walls and so will cause undermining of the base of the walls and cause collapse and $$

2) Breakwaters
- To protect coast and harbour
- They are able to absorb energy waves before they reach the coast
- Can either be build with one end attached to land or be offshore
- If it is offshore, it will form a calm zone of water behind it.
- Deposition of load occurs behind it
Negative impact:
Only water behind the coast is protected, but those away will be unprotected and cause erosion at other parts of the coast.

3) Groynes
- Built at right angles to coast
- Prevent longshore drift
- Help to absorb and reduce wave energy only at side of groyne facing longshore drift but not
at downdrift and so erosion occurs there
- To prevent erosion, groynes is angled at 5-10 degrees frm coast
Negative Impact
Erosion will still occur at other parts of the coast

4) Gabions
-Wired cages filled with crushed rocks
- Help to reduce erosion by reducing energy waves
Negative Impact
Only short term protection of 5-10 years
A lot of regular maintainence needed (corrode by seawater, excessive trampling, vandalism)
Very costly

Soft engineering measure which does not involve building of any physical structure buut focusses on planning and managing coastal areas and properties to prevent it from getting damaged by erosion.

1) Beach Nourishment
- Involves the replenishing of sand so as to increase beach quality and storm protection.
Negative impact:
Very expensive
Destroy natural habitat: Sand that is washed into sea will cover the coral reefs and prevent them from getting sunlight to survive.

2) Relocation of Property
- Green Line policy to restrict building of houses near to coastal regions where flooding might
occur
Positive impact:
A very useful policy as global warming is causing an increases in sea level and so it will help to prevent chances of building being affected

3) Planting of Mangroves
- Mangroves have prop, long, curved roots that prop up to trap sediments
- New anchorage of roots will cause the plant to trap enough sediments to form island
- It will be extending outwards to the sea
Negative impacts
Some coast cannot take the stress of the mangroves as they are affected by destructive waves
The depth of the coast with plants will be shallower and so hinders maritime trade

4) Stabilising Dunes
- Happens in places with large amts of sand and strong wind
- Wind will blow sand further inland
- Sand will pile up to form coastal dunes (Protect coast from sea)
- They are fragile and shrubs struggle to hold them in place

5) Coral Reefs
- Coral reefs help to reduce wavee energy in water
- If they die, then the waters will move at full force and cause erosion to take place
- Can be made artificially by using environmental materials and put in sea bed
- Help to enhance fishing opportunities and act as undersea barrier to reduce chances of
erosion.