Sediment cells REVISE - COASTS

Question 1

Concept

Answer 1

It is a concept with sources, transfers and sinks, it is important in understanding coasts as a system with both postive an negative feedback, it is an example of dynamic equilibrium

Question 2

Dynamic equilibrium

Answer 2

Sediment cells are dynamic because the sediment is constantly generated in the same region, transported through the transfer region and deposited in the sink region.
Coastal management in the source region may reduce sediment supply, e.g sea walls preventing cliff erosion. Management in transport region may reduce sediment supply going into the ink region for ex groynes trapping sediment to encourage beach building up.

Question 3

Sediment cell meaning

Answer 3

Is a littoral cell that links a system of sources and transfer and sinks of sediment along. Section of coastline.
Operates as a closed system with virtually no inputs or outputs of sediment form the cell. Contains inputs, outputs and transfers

Question 4

Examples of sediment cells

Answer 4

-Flambourough head - source region
- holderness coast- transfer zone
-spurn head - sink region

Question 5

INPUTS

Answer 5

• sources are placed where sediment is generated such as cliffs or eroding snd dunes. Some sources are offshore bars and river systems and these are an important source of sediment for the coast. E.x of sediment inputs are: cliff erosion, onshore currents, river transport, wind blown sediment from sand, sub aerial processes and marine organisms.

Question 6

TRANSFERS

Answer 6

-Places where sediment is moving along shore through longshore drift and offshore currents. Drift aligned beaches and parts of dunes and some ex are: longshore drift, swash, backwash, tidal currents, sea/ocean currents and wind.

Question 7

OUTPUTS

Answer 7

-depositional landforms and are crated including spits and offshore bars. Som ex of sinks are back shore (dunes), foreshore ( beaches), nearshore(bars), offshore depositional landforms (barrier island)

Question 8

POSITIVE feedback

Answer 8

When changes produces an effect that operates to increase the orgina change. E.g - when wind étions of a dune section during high velocity storms may remove stabising vegetation.

Question 9

Source region meaning

Answer 9

An eroding coastline

Question 10

Sink region meaning

Answer 10

Out building coastline

Question 11

Littoral zone meaning and context

Answer 11

Boundary between the land and sea.

This zone is constantly changing due to:
- short term factors such as waves, tides and seasonal storms.
-long term factors such as seal level change, climate change, human activity.

Question 12

FIX

Answer 12

Coastlines operate as a physical system. It is increasingly
understood that attempts to manage erosion on one small area
of a coast are unlikely to be successful unless the location is understood in a wider context. This context is the sediment cell. Long stretches of coastline operate as sediment cells. There are eleven of these around the English and Welsh
coast. In each cell are:

• Sources - places were sediment is generated, such as cliffs
  or eroding sand dunes; some sources are offshore bars. River
  systems are also an important source of sediment for the coast.
• Transfer zones - places where sediment is moving along the
  shore through longshore drift and offshore currents; beaches,
  parts of dunes and salt marshes perform this function.
• Sinks - locations where the dominant process is deposition;
  depositional landforms are created including spits and
  offshore bars.

Some coastal features may operate as both sinks and sources,
depending on whether the dominant processes are erosion or
deposition at a given time.
Sediment cells operate as a system with inputs, transfers and outputs of sediment. Under natural conditions the systems operate in a state of dynamic equilibrium with sediment inputs balancing outputs to sinks. For short per of time - for instance during a major storm that erodes a
spit - the system’s equilibrium might be disrupted but will tend to return to balance over time. Negative feedback mechanisms help maintain the balance by pushing the system back towards equilibrium:

During a major erosion event a large amount of cliff collapse may occur, but the rock debris at the base of the cliff will slow down erosion by protecting the cliff base from wave attack. Major erosion of sand dunes could lead to excessive deposition offshore, creating an offshore bar that reduces wave energy, allowing the dunes time to recover. Human intervention, in the form of coastal management, plus
threats such as a sea-level rise as a result of global warming, represent risks to the long-term dynamic equilibrium of sediment cells. These are examples of positive feedback which lead to disequilibrium in the coastal system:
Increased storminess could lead to long-term erosion of sand dunes with no chance to recover between storm events. Rising sea levels could increase the erosion of spits and estuaries, removing sediment faster than it can be replaced.