Lesson 7-How is sediment transported and deposited at the coast?

Question 1

Transportation process-Suspension

Answer 1

Very small particles of sand and silt are carried along by the waves and ocean currents.

Question 2

Transportation processes-Traction

Answer 2

Large stones and pebbles rolled along the sea bed

Question 3

Transportation processes-Solution

Answer 3

Dissolved minerals are transported within the sea water

Question 4

Transportation processes-Saltation

Answer 4

Small stones and pebbles bounce along in a ‘leap frog’ type action

Question 5

Accretion

Answer 5

Building up of beach

Question 6

How is sediment transported at the coast by the waves?

Answer 6

A large wave height does’nt mean its destructive

-Whether we get erosion or accretion depends on how the wave conditions on one day compare with the ‘normal’ wave condition.
-Beaches always to be balanced-neither eroding or accreting-they try to achieve this dynamic equilibrium, the beach might never be balanced but it is always trying to be
-At the end of summer, the beach is closest to equilibrium with the summer wave conditions

Question 7

Longshore drift

Answer 7

Waves approach beach at angle due to prevailing wind direction
-The waves break and the swash carries material up the beach at the same angle as the wave approached
-The swash dies away the backwash carries any material back down to the beach at a right angle due to the influence of gravity.
-Means that material is moved along the beach in a zig zag route.

Question 8

Do we always get longshore drift at the coast?

Answer 8

• Swash alligned coastlines are when waves break parallel to the coastline so there is no LSD
• Drift-alligned beaches allow LSD to occur as the prevailing wind approaches the beach at an angle

Question 9

What is the impact of coastal management on transportation?

Answer 9

• Management strategies distant transportation within natural patterns as it deprives beaches of material and accelerates erosion
  -stores, flows and sinks will be affected if longshore drift is interrupted

Question 10

What is coastal deposition and when does it occur?

Answer 10

• Occurs when sediment ecretes due to low energy

Question 11

What are examples of depositional landforms?

Answer 11

• Tombolos, Spit, Bars and beach

Question 12

What are conditions for deposition to occur?

Answer 12

• Almost 20% of the worlds conditions are depositional in nature known as accretion
  -occurs in low energy environments
  -sediement input from rivers and the precense of coastal currents tends to trigger deposits locally

Question 13

Factors influencing deposition

Answer 13

• Wave and wind direction, the supply of sediment and the depth of water are often significant.
• Large depositional landforms are found where the tidal range is less than 3 metres
• Waves need a stronger swash than backwash