Low energy coastline CS Flashcards
What are deltas?
landforms formed at the mouth of a river, where the river meets a body of water with a lower velocity than the
river (e.g. lake or sea), resulting in the reduction in the river’s capacity to transport sediment.
How do Deltas form?
The River meets the ocean at its mouth, which has a lower velocity causing the river to deposit material
This material slowly builds over time and cause a landform to form and split the river
These 2 new mouths continue to deposit material and cause another split and land to be formed
This continues to create a Delta
What is the low energy coastline study?
The Rhone Delta, France
Where is the Rhone Delta
Flows into the Mediterranean Sea just west of Marseilles
lies between 2 major tributaries of the river Rhone
Splits into many channels to form the delta but The Grand Rhone is the largest and carries 85% of the rivers water to the Mediterranean sea
What are the prevailing wind directions near the Rhone Delta?
Mostly from the NW which creates low energy waves, 0.8m-1m wave height 80% of the time
Waves from SSE and ESE are less frequent and represent 16% and 11% of the total annual regime
Why is the Rhone delta a low energy environment?
due to the small fetch from the mediterranean sea it means that waves have low energy
THis means that they deposit more sediment than is taken away
3 Physical factors that influence the Rhone Delta
The river collects a large amount of sediment from the young sedimentary rocks in the Alps
Deposition in 1900 was estimated to be 17 million m3 per year or 50 tonnes every minute!
The Rhone delta has formed over the last 7000 years since the sea level rise of the last ice age ended
What does flocculation mean?
the process where small particles suspended in water lump and form larger aggregates or flocs
How does the Formation of onshore bars and spits change over time on the Rhone Delta?
Due to Converging longshore drift currents, a small tidal range and low energy waves
Happens all along the coast with a spit forming at Beaduc
Needs a sustained period of time in a low energy environment
How does the Rhone Delta’s environment impact Low dunes behind beaches?
Dunes form when the winds blow from the sea, and dry sand is moved up the beach by saltation.
The sand become trapped by obstacles on the berm or the point of the highest spring tides.
Gradually these sand deposits will build up and become colonised by plants, such as marram grass, which are adapted to
salty conditions and have long roots to help them survive on shifting sands.
Over time dunes stabilise and the plants colonising them change as soils become established.
How does the Rhone Delta’s environment impact Increased rates of erosion of beaches and dunes?
The reduction in the load carried by the Rhone has led to coastal erosion problems, as erosion now exceeds deposition
Mediterranean sea level rise of 2mm/yr since 1950 plus increased storm activity has affected the delta, leading to reduced beach size and dune erosion
What areas have been impacted by a reduction in load carried by The Rhone?
Ste Maries de la Mer, the erosion rate is thought to be up to 8m per year, and is the urban area at greatest risk of erosion
Beach material is made of very fine sand (less than 0.2mm) which can easily be removed by coastal processes and Aeolian processes
Ste Maries de la Mer could be isolated from the land by 2035
