the rhone delta Flashcards
length of coast
90km
deposition per year
26 million tonnes of sediment in 1900
1.5 million tonnes in 2000 due to human influence
discharge
1,500m3 per year but can reach 6,000 m3 year in stormy conditions
geology
silt (fine unconsolidated sediment)
no faults or folds in rocks
no discordant or concordant coastline (all unconsolidated material)
when was the delta formed
7000 years ago when sea level rose after the last ice age
wave or fluvial dominated
wave dominated delta
so lobes of sand change shape by LSD
prevailing wind and fetch
NW (0m fetch)
small fetch (max 9000 km)
flocculation
small suspended particles group together at the mouth of the river
tidal range
microtidal
0.3m
short term change to delta
human intervention
west to East LSD
tidal range of 0.3m
erosion from waves and storm events
medium and long term change
change in volume of sediment from two rhone rivers
sea level rise of 2mm year
aeolian transport limited to sandy spits
human intervention
cell 1
SW-NE LSD
gracieuse spit formed
cell 2
W-E LSD
no spit due to water from grand Rhone
cell 3
LSD from two directions converges
Beauduc spit and bar formed
cell 4
long distance LSD
E-NW
L’Espiguette spit
high levels of sediment accumulation impact on landforms
gently sloping landscape
0.3-3 degrees
lagoons
formed when LSD moves sand to from bars
closed system
Dunes
aeolian transport
behind beach
face SE
brackish landforms
salt water marshes
e’tangs
sediment source
70% coastline supplies sediment for Beauduc and L’Espiguette
sand from the Rhone provides sediment for Gracieuse spit
human intervention
slat farms and Marseilles port are protected by artificial river dams
minimal
future of the Rhone Delta
2mm year sea level rise
caused inc erosion
winds from SE cause larrge wave surges which combined with decreased sediment input from rives, cause distort equilibrium
costal retreat of 2-8m year and therefore groynes, rip rap ad sea walls
