2.b - NILE DELTA CS LOW ENERGY

Question 1

what is lake El bullurus?

Answer 1

2nd largest lagoon found on the delta
saltwater and 175m deep at its deepest point

Question 2

what is lake Manzala?

Answer 2

largest lagoon in egypt
lagoons are enclosed by sand bars

Question 3

what are sand bars?

Answer 3

along the coast
are developed by EASTWARD LSD

Question 4

what are sabkahs?

Answer 4

salt flats
formed behing lagoons where older lagoons have dried out, leaving flat salt plains

Question 5

where are coastal dunes found (nile delta)?

Answer 5

developed between lakes manzala and El bullurus at Gamasa

Question 6

what are crescentric bars?

Answer 6

at alexandria
formed by rip currents and onshore waves, with little LSD

Question 7

what evidence is there that Nile delta is a low energy environment?

Answer 7

small waves
no erosional features like stacks or stumps etc

Question 8

what landforms would you expect to find on the Nile Delta?

Answer 8

depositional landforms:
beaches
bars and spits
lagoons forming
salt pans rather than mudflats, due to the heat

Question 9

what is a delta?

Answer 9

arge areas of sediment found at the mouths of many rivers

Question 10

what happens when the nile floods?

Answer 10

the river traditionally flooded annually, and these floods deposited vast amounts of sediment onto the delta flood plains, creating incredibly fertile soils (up to 9.6m deep around Cairo)

Question 10

what happens to nile sediment not deposited onto flood plains?

Answer 10

the sediment not being deposited on the flood plains will reach the Mediterranean Sea and be deposited due to flocculation
thus deposition is focused around the mouths of the distributaries.

Question 11

key features of the burullus lake

Answer 11

has an elongated elliptical shape
it is separated from the mediterranean sea by a narrow sand bar covered by sand mounds and sand dunes approaching up to 3m above sea level at its NE corner
agricultural wastes have been reported to increase sedimentation in wetlands and consequently diminish the size of lagoons such as Burullus.

Question 12

where do crecentric bars form?

Answer 12

to the east, cresentric bars form where the beaches are swash aligned, allowing rip currents to develop, which pull material out from the coastline and deposit it offshore

Question 13

how have dunes developed in the nile delta?

Answer 13

there is also an extensive ridge of dunes which has been developed between the 2 lagoons at Gamasa beach.
the dunes are about 30km across and result from the large backshore area being present here, the onshore winds allowing for aeolian processes to take place as well as the fact that dry warm conditions mean sand can dry out and be moved.
the winds coming in from the NW are able to entrain (pick up) huge amounts of sediment as the beach is up to 20km wide.

Question 14

how have coastal processes and sediment deposition combined to change the deltas morphology?

Answer 14

these coastal processes, combined w/ sediment deposition, have meant that traditionally the delta has been “growing”, extending out into the Mediterranean Sea, and reworked by the LSD moving eastwards/
the lagoons have, over time, been getting filled in by fine sediment which is no longer reworked by LSD

Question 15

what is happening to nile lagoons over time?

Answer 15

the lagoons have, over time, been getting filled in by fine sediment which is no longer reworked by LSD

Question 16

how will the landscape of the nile delta change over time due to building of the Aswan Dam, 1964

Answer 16

by FAR the most significant change to the region
done to ensure a water supply for the growing population of Egypt and produce HEP
it massively reduced the water and sedment supply downstream, and ∴ to the delta
about 120 mill tonnes of sediment used to flow, and now virtually none does, causing the delta to erode/retreat by up to 148m per year
areas most affected are by mouths of the distributaries due to lack of sediment supply
BUT eastern ends of the bars which help create the lagoons are still growing as the sediment is moved steadily eastwards by LSD
this has degraded the agricultural land as the soilds are less rich and fertile (which is significant as it is forcing people to move from traditional farming practises into fish farming in the lagoons, which is putting pressure on these fragile ecosystems)
if the bars which currently shelter them get eroded due to lack of sedimet supply are lost, the fish farming and economic potential is lost too
clearly this is an unsustainable approach as in time the landforms will be eroded fully.

Question 17

how will the landscape of the nile delta change over time due toconsistent wave and wind energy?

Answer 17

there are dominant winds (from NW in summer and NE in the winter)
these will steadily and consistenly rework sediment via LSD to increase the size of the onshore bars and spits
this process will be steady and regular, although the seasonal difference in winds will cancel out some of the LSD
this is a key physical factor shaping the landscape
the wind energy also moves sand from the Burullus sand bar landward, which then reduces the size of the Burullus Lagoon
the highway developed along the coast has not helped this as it has caused drying of the sand plus brought more people to the dunes, which has meant that the wind is now able to erode these dunes more easily

Question 18

how will the landscape of the nile delta change over time due to climate change?

Answer 18

sea levels are expected to rise between 18 and 64cm by 2100
this will increase flood risk and of the delta being inundated with sea water (which, being saline, could lead to farm land becoming infertile, thus having an enormous economic impact)
there could be up to 60% loss of farmland by 2100
the rate of coastal retreat will likelt increase, thus reducing the land available for human habitation
drinking water supplies and aquifers could be threated as well
this inundation ofn salt water is perhaps the biggest issue for Egypt as so many people and their source of income/water etc. comes from this

Question 19

what will change to landforms be like in the Nile Delta?

Answer 19

likely to be far more gradual and happen at an even rate compared to high energy coastlines (which will experience storms, causing arches to collapse eg)
the landforms to the west will lose sediment more rapidly whereas the ones to the east will benefit from sediment supplied via LSD
human actions could potentially significantly alter the rate of change in a positive manner through inputting sediment artificially/sea defences

Question 20

how will the damietta spit change over time?

Answer 20

becomes recurved due to wave refraction and secondary wind direcion
would get small due to no new sediment = western end gets thinner and potentially flooded by sea level rise
gradually migrate SE as wind blows in that direction

Question 21

how will the burullus lagoon change over time?

Answer 21

modified by erosion and deposition
sediment supply has decreased and sea levels increased => more energy/larger waves drown lagoons
dry out due to thermal energy =>
sea level rise may breach/erode bar
slow, LT change. bars vulnerable due to no new input

Question 22

how will the gamsa sand dunes change over time?

Answer 22

the seasonal changes in wind direction reshape dune and creates ridges
can travel along beach (aeolian) SOUTHWARDS
fairly significant changes
gets smaller due to lack of sediment input
increased tourist use of dunes destroys vegetation

Question 23

how will the rosetta onshore bar change over time?

Answer 23

same as damietta spit
extend to form lagoon
smaller and sea levels increase
deprived of sediment from dam

Question 24

how will the sabkahs change over time?

Answer 24

takes 1000s of years to change and build up layers of salt crust
lagoons drained for farming therfore more sabkahs over time

Question 25

how will the cresentric bar at alexandria change over time?

Answer 25

coastal management

Question 26

what is the damietta spit’s interrelationship with other landforms in the delta?

Answer 26

could become a bar
bars trap water in behind to form lagoons

Question 27

what is the burullus lagoon’s interrelationship with other landforms in the delta?

Answer 27

either side of ridges/headlands (the depressions between them)
on the periphary of the lagoon flocculation leads to deposition of fluvial sediment and evaporation = sabkahs

Question 28

what is the gamsa sand dune’s interrelationship with other landforms in the delta?

Answer 28

between Manzala and Bullurus
if beaches disappear due to sea level rise dunes will have no sediment input and will deflate

Question 29

what is the rosetta onshore bar interrelationship with other landforms in the delta?

Answer 29

to the east of where the Rosetta distributary mouth reaches the sea

Question 30

what is the sabkah’s interrelationship with other landforms in the delta?

Answer 30

behind lagoons/ where old lagoons have dried out

Question 31

what is the cresentric bar at Alexandria’s interrelationship with other landforms in the delta?

Answer 31

bars absorb wave energy so it reduces it
by time it reaches beach = more deposition (positive feedback)

Question 32

how are the Burullus lagoon and Rosetta Bar interlinked?

Answer 32

as bar forms due to LSD, they extend to enclose lagoon
lack of new sediment erodes bar = lagoon breached

Question 33

how could building coastal defences influence the Nile delta coastline and sediment budget?

Answer 33

reduced sediment supply has led to erosion of the coastline most notably around mouths of distributaries Rosetta and Damietta
this can be viewed as an unintentional change to coastal environment as the Aswan Dam was intended to manage River Nile and generate HEP rather than change the coastline, but it almost certainly has had an impact