The coastal system

Question 1

what is negative feedback?

Answer 1

It’s when a change in the system causes other changes that have the opposite effect eg. as a beach is eroded the cliff behind it gets exposed to wave attack, the sediment eroded from the cliff is deposited on the beach causing it to grow in size again

Question 2

what is positive feedback?

Answer 2

It’s when change in the system causes other changes that have a similar effect eg as a beach forms it slows down waves which can cause sediment to be deposited, increasing the size of the beach

Question 3

what are the sources of energy in the coastal system?

Answer 3

wind, waves, tides and currents

Question 4

how does wind create energy in the coastal system?

Answer 4

• winds are created by air moving from high to low pressure
• during storms the pressure gradient is high and winds can be strong
• strong winds generate powerful waves, with strong prevailing winds creating higher-energy waves than winds that change direction

Question 5

How do waves create energy in a coastal system?

Answer 5

• waves are created by friction caused by wind giving it a circular motion
• effect it has on the shore depends on the height which is affected by wind speed and fetch, high wind and long fetch create high and powerful waves
• waves break at shore, with the friction of the sea bed slowing the bottom of the waves making their motion more elliptical
• the stronger the swash and weaker the backwash means sediment is deposited

Question 6

what is the fetch?

Answer 6

The distance that the wind has travelled across open water whilst creating waves

Question 7

what are constructive waves?

Answer 7

A wave with a low frequency and are low and long, that deposits material up the beach after it breaks, deposits it, building up the beach. The swash is stronger than the backwash.

Question 8

what are destructive waves?

Answer 8

High and steep waves with a high frequency, the backwash is stronger than the swash which erodes material from the beach

Question 9

how do tides create energy on a coastline?

Answer 9

• tides are caused by the gravitational pull of the moon and sun and are the periodic rise and fall of the ocean surface
• tides affect where the wave breaks on the beach, with the area between high and low tide where most land forms are created and destroyed

Question 10

how do currents supply energy to a coastline?

Answer 10

• current can be caused by wind or variations in water temperature and salinity
• currents move material along the coast
• rip currents
• upwelling- is the movement of cold water deep in the ocean to the surface, replacing the warmer water with nutrient rich currents

Question 11

what are some inputs on the coast?

Answer 11

• eg. sediment can be brought into the system in various ways, but energy inputs are wind, waves, tides and currents
• geology
• sea level change

Question 12

what are some outputs on the coast?

Answer 12

• eg. sediment can be washed out to sea, or deposited further along the coast
• dissipation of wave energy

Question 13

what are some transfers on the coast?

Answer 13

processes such as erosion, weathering, transportation and deposition

Question 14

what are some stores on the coast?

Answer 14

land forms such as beaches, dunes and spits

Question 15

What are high energy coasts?

Answer 15

• They receive high energy inputs from large, powerful waves which are caused by strong winds, long fetches and steeply shelving offshore zones.
• Steady prevailing winds
• They tend to have sandy coves and rocky land forms such as cliffs or caves
• higher rate of erosion than deposition

Question 16

what are low energy coasts?

Answer 16

• They receive low inputs of energy in the form of small, gentle waves
• They can be caused by gentle winds, short fetches and gently sloping offshore zones
• Some might have a reef or island offshore
• They often have salt marshes and tidal mudflats
• The rate of deposition is often higher than the rate of erosion
• Typical landforms are beaches and spits

Question 17

Where are inputs of sediment brought to coastal systems from?

Answer 17

• Rivers carry eroded sediment from inland
• Sea levels rising can flood river valleys, forming estuaries
• Eroded from cliffs
• Waves, tides and currents can transport sediment into the coastal zone from offshore deposits

Question 18

What is the sediment budget?

Answer 18

• The difference between the amount of sediment that enters the system and the amount that leaves
• And requires identifying all sediment sources and sinks to calculate it

Question 19

What does a negative sediment budget lead to?

Answer 19

retreating coastline

Question 20

What are sediment cells?

Answer 20

Lengths of the coastline that are self contained for the movement of sediment, which means that processes going on in 1 cell doesn’t affect the movement of sediment in another- making it a closed system

Question 21

How many sediment cells are there in the UK?

Answer 21

11

Question 22

What type of equilibrium do coastal systems normally operate in, and what does it mean?

Answer 22

• Dynamic equilibrium

- inputs and outputs are balanced

Question 23

What are the specific zones on the coastline/beach?

Answer 23

• Backshore
• Foreshore
• Inshore
• Offshore
• Nearshore

Question 24

What is the backshore?

Answer 24

• area between the high water mark and the landward limit of marine activity
• Changes only normally take place here during storms

Question 25

What is the foreshore?

Answer 25

• area between the high and low water marks

- Its the most important zone for marine processes in times that are not influenced by storms

Question 26

What is the inshore?

Answer 26

-area between the low water mark and where waves cease to have an influence on the land beneath them

Question 27

What is the offshore?

Answer 27

-area beyond the point where waves cease to impact the seabed and where activity is limited to deposition

Question 28

What is the nearshore?

Answer 28

• area extending seaward from the high water mark to the area where waves begin to break
• it includes;
• swash zone-turbulent layer where waves break
• surf zone-where waves break and where swash moves up the beach
• breaker zone- where waves approaching the coastline begin to break with a water depth of around 5 to 10m

Question 29

What is wave refraction?

Answer 29

• when waves approach an irregular shape coastline they are refracted and become increasingly parallel
• the overall effect is that the wave energy becomes concentrated on the headland, causing greater erosion
• with the lower energy waves spilling into the bay causing bay deposition

Question 30

what is the difference between neap and spring tides?

Answer 30

• spring tides are the highest monthly tidal range produced when the moon, sun and Earth are in a straight line
• Whereas neap tides are the lowest monthly tidal range, produced when the sun and moon are 90 degrees to each other in relation to the earth

Question 31

What are tidal surges?

Answer 31

Meteorological conditions give rise to strong winds which produce higher water levels than those at high tide