Coastal Landscapes - CASE STUDIES

Question 1

Where is the Rhone Delta located?

Answer 1

In the Mediterranean Sea between the Grande and Petit Rhone.

Question 2

How much water is transported by the Grand Rhone into the Mediterranean?

Answer 2

Around 85%.

Question 3

How has the Rhone Delta formed?

Answer 3

Sea level rise at the end of the last ice age (over 7000 years ago).

Question 4

How has the shoreline been modified?

Answer 4

After a flood in the 18th century, one of the channel’s courses was disrupted and sediment moved to form Beauduc Spit.
In the 19th century, human management reduced the 3 channels into one (decreased fluvial sediment and discharge).

Question 5

What is the total length of the coastline?

Answer 5

90km.

Question 6

Why is the Rhone Delta a low-energy coastal environment?

Answer 6

Fetch distance is short (900km from SW - contributes 30% of waves).
Dominant NW wind direction has low speeds.
Therefore, waves are low in height and energy (SW wave heights from 0.5m to 1m)

Question 7

Deposition statistics…

Answer 7

17 million m3/year in 1900
Is affected with seasonality (can change from 1500 m3/sec to 6000 m3/sec)
In 2000, 1.5 million tonnes of sediment was carried per year.

Question 8

What causes the high deposition rate within the Rhone Delta?

Answer 8

Flocculation of clay particles (salt water from saline Mediterranean and fresh water) causes clay particles to stick together.
Small tidal range of 0.3m = current can’t carry sediment away.

Question 9

What are recent changes that have occurred within the Rhone Delta?

Answer 9

Sea level has risen by 2mm/year since 1950
Increased storm activity = increased erosion of beached and dunes
Coastal retreat between 2mm - 8mm.
Equilibrium is being restored by groynes, sea walls and rock armour.

Question 10

Where is Saltburn to Flamborough Head located?

Answer 10

Sub-cell 1d of sediment cell 1, located on the south-west of the North Sea.

Question 11

How long is the coastline?

Answer 11

60km.

Question 12

Why is this a high-energy coastal environment?

Answer 12

Dominant waves are coming from the N and NE.
1500km fetch (strong winds and wide area from North Sea)
Difference in wave energy inputs is caused by varying resistance and and geologies (shale, clay = 0.8m/yr and limestone = 0.1m/yr)

Question 13

What other coastal landforms are seen along Saltburn-Flamborough?

Answer 13

Cliffs - horizontally bedded, covered by glacial till, made up of chalk, steeper profiles.
Shore platforms - rocky, can be seen at Robin Hood’s Bay, can slope from 1 to 15 degrees, max. width of 500m
Geos and Blowholes - over 50 geos, chalk and boulder clay has collapsed into the sea caves.
Beaches - eg. Scarborough and Filey Bay,

Question 14

How can the landforms along Saltburn-Flamborough be modified over time?

Answer 14

Eustatic rise can alter whether a landform will be modified greatly over time.
An increase in cliff retreat due to the resistant geologies of rock = occasional rockfalls/landslides.

Question 15

Where is Sandbanks Peninsula located?

Answer 15

In Dorset, which separates Poole Harbour from Poole Bay.

Question 16

Strategies to manage Poole and Christchurch Bay.

Answer 16

Hold the Line (HTL): maintaining/improving existing defences.
Managed Realignment (MR): existing defences moved to sustainable positions (further inland).
No Active Intervention (NAI): Areas of low economic and high environmental value aren’t protected.

Question 17

Why is there a need for management at Sandbanks Peninsula?

Answer 17

High-value commercial properties that provide employment and generate spending in the local community.
Beach has become a main tourist destination.
At the end of the peninsula is the harbour used by ferries and commercial ships that carry goods.
Longshore drift could cause the harbour’s entrance to become clogged/shallow.

Question 18

How can climate change alter the landscape of Sandbanks?

Answer 18

Sea levels are predicted to rise by 0.6m in the next 100 years = could cause flooding of properties and breach the peninsula.
Peninsula could be cut off from the mainland and could cause around £18m of damage to residential properties in the next 20 years.

Question 19

What are some management strategies and their impacts that affect Sandbanks?

Answer 19

Rock groynes - minimises movement of sediment by LSD. Keeps access free for ships, absorbs wave energy, and reduces the rates of erosion.
Beach recharge - conserves beaches. Over 3.5 million m3 of sediment has been added back onto the Poole Bay beaches. Example of attempting to work with nature.

Question 20

Where is the Mangawhai-Pakiri coastline located?

Answer 20

In New Zealand.

Question 21

What are the main uses for sand in New Zealand?

Answer 21

Construction - mainly for commercial and residential buildings due to rising population in Auckland, 20km away from coastline (pop. 1.5 million = contributors to 35% of country’s GDP).
Beach replenishment - mainly tourist beaches in Auckland.

Question 22

What else is contributing to the growth of Auckland’s development?

Answer 22

Business/Finance/High-tech industries
Tourism, mainly of the coastal areas (2015 had record of 2.3 million tourists)

Question 23

Statistics of nearshore sand dredging along Mangawhai-Pakiri coastline

Answer 23

1994 - 2004 = 165,000 m3/year was extracted @ Mangawhai
2005 - 2020 = Sand extraction moved to Pakiri Beach with a rate of 75,000 m3/year

Question 24

Where does sand mainly come from to supply the beaches?

Answer 24

OFFshore - sediment budget is a closed system and outputs of sand aren’t replaced by inputs from rivers/offshore waves. Overall sand supply has decreased on sand dunes, beaches and sea bed.

Question 25

What are the main impacts of sand mining on coastal landforms along Mangawhai-Pakiri?

Answer 25

Beaches are becoming wider and flatter = leads to ineffectiveness when absorbing waves.
Foredune ridges are undercut by waves = develops steep, seaward-facing scarps
Increased rates coastal erosion = less natural defences for storm events, and can lead to long-term retreat.

Question 26

What happened to the base of the Mangawhai spit back in 1978? How did it impact the overall area?

Answer 26

A 28m breach was discovered due to the storm surge. A second breach also occurred, which led to:
Altered tidal currents
Sedimentation of Mangawhai spit
Shallow water exposed waterfront community

Question 27

How will climate change affect the Mangawhai-Pakiri coastline?

Answer 27

Increased coastal retreat due to the past reduction in sand accumulation
Long-term retreat = 35 metres
Width of coastal area susceptible to erosion = 48-111 metres