1. Offshore bars Barrier beaches and islands
Origin and development of landforms and landscapes of coastal deposition
Offshore bars
Barrier beaches and islands

2. offshore bar - also called breakpoint bar or longshore bar

3. Offshore bars A ridge of sand lying parallel to the coastline
Located offshore on the seaward side of the breaker zone (where waves first break ) so also called a breakpoint bar
Semi-submerged by the tide - unlike barrier beaches and islands
Formed from the sediment transported down the beach by backwash - therefore located at the lowest limit reached by the backwash of breaking waves (LWM = low water mark)
May be more than one bar - the outer bar related to the breaking point of storm waves and the inner bar to normal waves
Offshore bars are linked directly with the beach system unlike barrier beaches and islands

4. offshore bar - also called breakpoint bar or longshore bar

5. Barrier islands in Florida

6. Barrier islands in New York

7. Barrier beaches and islands
An elongated sand or shingle bank which lies parallel to the coastline
Not submerged by the tide even at high tide
Separated from the mainland by a lagoon - lagoons also called sounds
Separated by tidal inlets - creates a chain of offshore islands
May have sand dunes behind the beach
Saltmarsh (non-tropical coasts) or mangrove swamp (tropical coasts) may develop on fringes of lagoon
Make up 10-15% of the world’s coastlines
Barrier islands tend to migrate landwards - caused by washover or overtopping of material in storms - if they are pushed onshore they are transformed into barrier beaches

8. Barrier beaches and islands

9. Barrier beaches and islands
Could be formed by the breaching of a spit in a storm or by strong river currents - the original sediment input would have been from headland erosion and longshore drift along the coast before the spit breached
Could also have been formed by the landward movement of offshore sediments with the post-glacial sea level rise e.g. at Chesil Beach - constructive waves deposit sediment to form a barrier beach in front of the land
Could simply be created by rising sea levels which flood the low lying land behind a beach and its sand dunes
Barrier beaches and islands are typically found on low gradient coasts with a big supply of sediment (means a large beach can build up) and where the tidal range is low (means tidal currents are weak and do not interfere with deposition)

10. Barrier islands and beaches

11. Examples of barrier beaches and islands
Eastern coast of the USA from Florida to New Jersey e.g. Cape Hatteras (N. Carolina), Long Island (New York)
Chesil Beach, UK
The Lido of Venice
The Frisian Islands off the Netherlands and Germany

12. Eastern seaboard of the USA
Cape Hatteras

13. Cape Hatteras

14. Venice Lido
The Lido

15. The Venice Lido
A sand bar along the Adriatic Sea coastline of N. Italy
11 km long
One of two main barrier islands separating the Adriatic Sea from the mainland
The salt water lagoon behind the barrier island is called the Laguna Veneta
Venice is located on one of the islands in the lagoon behind The Venice Lido
Lagoon largely enclosed by the barrier beaches - only three tidal inlets linking lagoon with the sea - results in very high variations in water level in the lagoon especially at spring tide - regularly floods Venice (the acqua alte or ‘high water’)
Formed about 7,000-6,000 BP when breaking waves formed sand shoals offshore as sea levels were rising after the Ice Age

16. The Venice Lido

17. Frisian Islands
The Frisian Islands

18. Frisian Islands
A chain of islands stretching over 500km along the coasts of the Netherlands, Germany and Denmark in NW Europe
Located between 5 and 30km off the mainland
The West Frisian Islands (off the coast of the Netherlands) and the East Frisian Islands (off the coast of Germany) are barrier islands formed about 7,000-6,000 BP when breaking waves formed sand shoals offshore as sea levels were rising after the Ice Age
Once specialised plants colonised the sand banks the sediment was stabilised and the barrier islands were formed
The islands are continuously migrating from west to east as a result of wave action

19. Frisian Islands

20. Chesil Beach
Chesil Beach

21. Chesil Beach

22. Homework task
Compile a brief case study about the barrier islands linked with Long Island, New York. The information should be presented around a map(s).
Include:
Named barrier islands, beaches, tidal inlets and lagoons with facts/figures
Recent physical change(s) linked with specific high energy weather events
Key feature(s) of the human geography