Dunes

Question 1

Introduce

Answer 1

Sand dunes are a distinctive coastal feature and specialized habitat.

Dunes form where an obstacle such as a shingle ridge or vegetation traps a supply of dry, wind-blown sand.

Question 2

What are the essential ingredients for a dune…

Answer 2

Active dune systems require

Sediment input from offshore to build a beach (sediment supply)
Availability of sediment on beach (lack of stabilisers)
Wind (transport capacity) to transport sediment from beach onshore
Space onshore for dunes to grow (lack of houses/cliffs)
Time for dunes to build between destructive storms

Question 3

What type of beach is required for a dune?

Answer 3

High wave energy (wide surf zone)
Least flow disturbance (flat beach)
Largest sediment availability (beach not covered in waves)
Steepness reduces transport capacity

Question 4

On dune coasts the plants have to cope with…

Answer 4

The drying and tearing action of the wind
Abrasion
Salt spray
Saltwater flooding
Heat, drought
Burial in sand 
A limited supply of nutrients. 

In addition, the wind blows the seeds away from the open sand surfaces and therefore hinders the spread of a vegetation cove

Question 5

(Wolfe and Nickling, 1993)

Answer 5

Even a sparse vegetation cover will weaken the power of wind, shelter the ground surface and trap sand grains

Question 6

How do dune plants survive?

Answer 6

Dune plants are xenomorphic, i.e. they have adapted to tolerating dryness.

They have long roots that reach down to the lower, humid sand layers, and their stems can survive bending by the wind.

Question 7

Hesp (2011) Dune Coasts

What are the four main coastal dune types?

Answer 7

Foredunes
Blowouts
Parabolic dunes
Transgressive dunefields

Question 8

Hesp (2011) Dune Coasts

What is the crucial first factor in determining whether dunes can form or not?

What is the next factor crucial for dune development (not sand supply)?

Answer 8

Wherever there is a minimal sand supply to build a beach, there will exist the potential for a sand dune to form.

The wind energy above a minimum threshold velocity.
The higher the wind energy, the greater the potential for dune development, particularly for those coasts with prevailing onshore winds.

Question 9

Hesp (2011) Dune Coasts

What does the degree and type of dune development depend on the ability of?

Answer 9

Pioneer plants to colonize the backshore and maintain overall stability even during periods of storm erosion, or rapid accre­tion/progradation, or not.

Question 10

Hesp (2011) Dune Coasts

The dominance of plants colonizing and maintaining a presence on the backshore has led to the development of…

Disturbance of the vegetation cover by wind, wave, or climate mechanisms led to the development of…

In some cases, a high sediment supply, or climatic conditions (e.g., arid or semi-arid), restricted plant cover, and high wave and wind energy led to the development of…

Answer 10

foredunes and foredune plains.

blowouts and parabolic dunes.

mobile (transgressive) dunefields.

Question 11

Houser and Ellis (2013) - beach and dune interaction

Transport of sediment on the backshore is dependent on…

In general, grains will be moved by the wind when…

Answer 11

the ability of onshore winds to entrain and transport more sediment from the beach to the dune than is lost from the dune during storms that erode the dune.

the fluid forces of lift and drag overcome the effects of the weight of the particle and cohesion between adjacent particles.

Question 12

Where is the largest dune area in England?

Answer 12

The Ainsdale Sand Dunes National Nature Reserve (NNR) on the Sefton Coast (totals 508 ha)

Question 13

The ecosystems of the dunes have been and are being modified by human activity. Four key examples of this are:

Answer 13

1) Pine plantations – past and present
2) Golf courses
3) Visitor pressure
4) Conservation of fixed dunes

Question 14

What is zonation?

Answer 14

Refers to the variation of species or communities over a particular area.

For example, variations in salt spray, inundation and the height and salinity of the water table will result in different species occupying (or tolerating) different areas of the dune.

Question 15

Threats to sand dunes by people

Answer 15

Interception of long-shore drift due to the construction of jetties.

Removal of sand for mineral extraction.

Visitor pressure: trampling, horse- riding, bike scrambling.

Pollution from agriculture - nutrient enrichment.

Afforestation.

Levelling for industrial development, housing, airports etc.

Drinking water abstraction.

Conversion into agricultural land.

Question 16

Case study: Ainsdale Sand Dunes – A Successful Integrated Management Approach

Intro

Answer 16

Outstanding area of wildlife interest.

The area has many conservation designations, including:

• Ramsar Site
• Special Protection Area (SPA)
• Site of Special Scientific Interest (SSSI)
• Special Area of Conservation (SAC).

Question 17

Case study: Ainsdale Sand Dunes – A Successful Integrated Management Approach

Two main threats to this particular resource are identified:

Answer 17

1. Scrub and growth of rank vegetation. In particular the invasion of non-native pines and poplars and the establishment of rank grasses and herbs such as brambles.
2. Public pressure. Ainsdale beach is a popular tourist area which leads to dune erosion and loss of habitat quality. 5 million people living within 1 hour’s drive of the area. Associated activities such as vandalism, fire and the collection of rare species also cause considerable damage.

Question 18

Case study: Ainsdale Sand Dunes – A Successful Integrated Management Approach

This multi-purpose approach is delivered through a range of management strategies:

Answer 18

Scrub cutting and clearance which is carried out in relatively small areas, due to the labour intensive nature of this activity

Mowing to control the height and density of invasive species in the dune slacks.

Grazing by sheep and cattle has been reintroduced (1990), controlling target species such as Creeping Willow.

Dune stabilisation and restoration works have been used in areas where property or infrastructure is threatened.

Species management, for example breeding pools for toads and fencing to separate visitors from the lizards.

Question 19

All…

Answer 19

Introduce

Type of beach

On dune coasts the plants have to cope with..

Hesp (2011)

Houser and Ellis (2013)

Wolfe and Nickling (1993)

Ainsdale Sand Dunes National Nature Reserve (NNR) case study