Beaches and Sand Dunes

Question 1

What are the 8 coastal zones?

Answer 1

Backshore zone, foreshore zone, swash zone, beach zone, littoral zone, nearshore zone, surf zone, offshore zone.

Question 2

What is the littoral zone?

Answer 2

this is the area where sediment is moved by the action of waves.

Question 3

How much do beaches account for on coast?

Answer 3

20% sandy

10% cobble

Question 4

Why are muddy coasts removed from the term beach?

Answer 4

because they behave differently due to the cohesisvity of muddy substrate.

Question 5

How does the steepness of cobbley and sandy beaches vary?

Answer 5

sandy beaches have a gentle gradient and cobble beaches have a steeper gradient. sandy beach profile helps to dissipate the energy of waves over large range. accumulate sands in the summer increasing their steepness and remove sands during the winter decreasing steepness. cobble beaches increase steepness during storm events.

Question 6

what effects how a beach responds to changes in the environment?

Answer 6

beach sediment size.

smaller the sediment the more muted the change.

Question 7

What is the beach water table?

Answer 7

this is the top of the groundwater that underlies the beach, it flows under the backshore features and effects the shape of the foreshore, berm.
hydraulic gradients may lead to seepage.

Question 8

What is the beach berm?

Answer 8

this is the limit of the swash zone where sediment is deposited, characterised by a flat plateau at the swash zone limit.

Question 9

What are beach cusps?

Answer 9

formed from rip current cells and the associated inner bars that lead to cusps opposite the rip channels and horns opposite feeder current divides.

Question 10

What are rip currents?

Answer 10

water moved by wave set up needs to flow back to deep water, it returns through the path of least resistance along channels between sandbars, jetties and piers.
characterised by discoloured waters, no breaking waves, floating debris etc.

Question 11

What are the pressures exerted on sand dune organisms?

Answer 11

• high salinity
• temperature stresses
• low nutrient availability
• water stresses
• unstable sediment

Question 12

what are coastal sand dunes?

Answer 12

sedimentary deposits of sand formed by the transport of sand from the beach (source) by onshore winds to the back of the beach. sand size = 0.15 - 1 mm

Question 13

what are the 2 types of sand dunes?

Answer 13

impeded and transgressive (free).
impeded sand dunes are those fixed by vegetation.
free dunes are readily mobilised and therefore result in dunes that reflects the primary patterns of wind.

Question 14

What are the parts of a dune?

Answer 14

embryo, foredune and secondary dune system.
foredune is considered the primary dune formation, lies parallel to the beach and reflects wave action.
secondary dune system reflects a stabilised dune and can be used to mark the position of previous shoreline.

Question 15

what are the results of disturbances on the dunes?

Answer 15

May be natural or unnatural. results in the destabilisation of foredunes or older dunes, may result in bowl shaped blowouts to parabolic dunes.

Question 16

What are the effects of vegetation on dunes?

Answer 16

colonising plant communities cause the critical shear stress to increase and the boundary shear stress to decrease. they do this by stabilising the sand with their roots, providing organic material altering the nutrient level within dunes, protecting the surface layer of the dune and reducing wind strength.

Question 17

What species make up a dune.?

Answer 17

Early species 0 - 50 yrs. Beach grasses and sand reed grasses. High dispersal rates and fast growing.
Middle species 55 - 175 yrs. Evergreen shrubs (juniper) and bunchgrasses. Good dispersal abilities.
Late species 200+ yrs. mixed pine forests. lower dispersal rates and higher nutrient requirements.

Question 18

Why are sand dunes important?

Answer 18

provide an important habitat for organisms and provide protection for infrastructure behind it.

Question 19

How should dunes be managed?

Answer 19

dunes must be protected to reduce the amount of human activity. planting vegetation, using sand traps and minimising accessibility to area is important.

Question 20

what is stress?

Answer 20

force applied over a specific area.

Question 21

How does swash effect the sandy beach gradient.

Answer 21

swash = swashup and backwash. swashup has more energy than backwash. constructive waves with long periods means that the swash of one wave is not affected by the backwash of the previous wave. this means that the swash has maximum amount of energy as possible, moving sediment up the beach, increasing the gradient. In contrast destructive waves cause swash and backwash to collide, dissipating the energy and movement of sediment up the beach. Due to the wave run-up created from the waves their is a high pressure system against the shoreline. This forms strong currents moving away from the shore, taking sediment with them.

Question 22

Give examples of natural sediment traps?

Answer 22

Bay heads, spits, cuspate foreland, deep sinks.

Question 23

What conditions do sand dunes require?

Answer 23

available area landward of the beach, suitable sediment supply, onshore winds, high tidal range, gentle gradients, colonising vegetation.

Question 24

What happens when dunes are supplied with a + sediment budget.

Answer 24

Propagate seawards, forming a series of dune ridges.

Question 25

Why may sea level be responsible for sand dune formation?

Answer 25

waves able to push further up the beach, more sand is deposited to the back of the beach, onshore winds move the sand further back, accumulating around features, dunes form.

Question 26

Why may the Severn estuary be both an estuary and a delta?

Answer 26

Delta because there are periods of deposition, neap tides, but then eroded during spring tides, creating sediment starved estuary.