case study- low energy coastal environment

Question 1

where is the location of study

Answer 1

The Rhone Delta- South France

Question 2

Where does the Delta flow into?

Answer 2

flows into the Mediterranean Sea, just west of Marseilles in South France

Question 3

what does the Delta lie between?

Answer 3

two distributaries of the river rhone:
-The grand rhone
-The petit rhone
-They divert 4 km north of Arles

Question 4

how many kilometres is it from the sea to the point the distributaries diverge

Answer 4

30km

Question 5

what is the grand rhone

Answer 5

The biggest distributary which carries 85% of Riverwater to the Mediterranean

Question 6

when was the Delta formed and why?

Answer 6

formed over last 7000 years since the flangian transgression

Question 7

what happened in the 18th century to the Delta?

Answer 7

The coastline began to take shape when the flood moved the channels course to present day position
-Led to material at mouth of abandon channel being moved to form beudac spit

Question 8

what happened in the 19th century to the Delta

Answer 8

The mouse of the grand rhone changed position due to human management, reducing three channels to one

Question 9

What’s the total length of the coastline?

Answer 9

90 km

Question 10

how big of an area does it cover?

Answer 10

1740 km²

Question 11

what is the shape of the delta?

Answer 11

Lobate shaped

Question 12

What is a delta dominated by?

Answer 12

waves that reshape the delta by moving sediment at the edge of the delta by longshore currents

Question 13

what are the deposits typically?

Answer 13

Sand and silt with coastal beaches of fine sand

Question 14

how is it a low energy coastal environment?

Answer 14

1. the enclosed shape of Mediterranean equals short fetch distances in all directions
2. The dominant wind direction is north-west and has low windspeeds.
3. As a result of both above waves, have low energy and height.
4. high levels of sediment accumulation from river deposition= gently sloping coastal landscape, where waves break early onshore energy is dissipated by beach and delta sediment

Question 15

what is the distance of the longest fetch, and from which direction?

Answer 15

Longest fetch equals 900 km from Southwest, but interrupted by the balearic islands

Question 16

How much is deposited per year?

Answer 16

17,000,000 m³ per year or 50 tons per minute in 1900

Question 17

how does river flow vary and what does it affect?

Answer 17

River flow, varies seasonally with typical discharge being 1500 m³ per second in high flow conditions, so deposition various seasonally too.

Question 18

what is high deposition rates due to?

Answer 18

Flocculation of clay particles
-Mediterranean= very saline, so when salt mixes with freshwater clay particles stick together and I’ll deposited as they are too heavy to be carried in suspension

Question 19

What type of tide does it have?

Answer 19

microtidal range of 0.3 m

Question 20

what is a small tidal range mean?

Answer 20

very few currents are created to carry material away

Question 21

why did the amount of material carried away fall and when

Answer 21

in the 20th century the amount of material carried fell as rhone river was managed to prevent flooding and for hydro electricity production
-In 2000= 1.5 million tons per year

Question 22

what are the three spits called?

Answer 22

-spit of espiguette
-spit of beauduc
-spit of gracieuse

Question 23

what are the two etangs called?

Answer 23

-etang de l’imperial
-etang de melegal

Question 24

what is the port called in the mouth of the rhone Delta?

Answer 24

Port st louis

Question 25

how much has authority spent on coastal protection?

Answer 25

€15 million on coastal protection such as
-groynes
-rip rap
-sea walls

Question 26

what are the recent changes?

Answer 26

-climate change and temp increase impact the Mediterranean
-Rise in sea levels= 2 mm per year since 1950
-Increase activity= increase erosion, rates of beaches and dunes

Question 27

is the system balanced?

Answer 27

NO, Although tidal range is small winds from SE result in large wave surges and reduced sediment input from rivers which lead to an unbalanced in input and output in the system which results in rates of coastal retreat between 2 to 8 m

Question 28

what is the two main directions of waves?

Answer 28

-Most frequent= SW= 30% of regime
These bring low energy waves with heights of 0.5 to 1 m, 80% of the time
-Waves from SSE and ESE or less frequent and represent 16% and 11% of total annual regime
These bring high wave energy more than 2 m high in more than 40% of cases
-These are associated with unsure wins from SSE + SE who is speed can exceed 100 km an hour

Question 29

Characteristics of cell one

Answer 29

dominated by SW-NE LSD, which formed Gracieuse spit across entrance of port st louis

Question 30

characteristics of cell 3

Answer 30

Has converging LSD current resulted in formation of onshore bars

Question 31

what can be seen all along the coast?

Answer 31

Lagoons/etangs where LSD has moved sand to trap water

Question 32

What do coastal beaches look like?

Answer 32

Very narrow with low dunes behind
-Behind dunes, there are brackish, ponds/lakes and lagoons

Question 33

what is landform is in the near shore area?

Answer 33

-They are longshore bars where backwash removes and deposit sand between these. There are longshore troughs.

Question 34

how do dunes form?

Answer 34

They form when wind blows from sea and dry sand is moved up the beach by solution. The sand becomes trapped by obstacles on the berm and eventually sand deposits, and becomes colonised by plants.

Question 35

what is an example of a plant on the delta?

Answer 35

marram grass

Question 36

how are plants adapted to their environment?

Answer 36

They are adapted to salty conditions and have long roots which helps them survive in shifting sand

Question 37

what do grasses do on dunes?

Answer 37

they trap sand and form embryo dunes, which grow to form ridges and overtime, the dunes stabilise