CASE STUDY - NILE DELTA - low energy coastal environment

Question 1

background info

Answer 1

• northern Egypt (where Nile meets Med sea)
• formed 3000+ years ago bc deposition exceeded marine erosion
• the delta splits into distributaries - used to have lots but now only 2 remain - flood control and sediment loss reudced sediment delivery to the coast

Question 2

physical factors affecting landforms - currents and wind

Answer 2

CURRENTS
- nearshore currents move sediment along coast (ocean plays little role)
- EG –> Parallel bars east of Abu Qir from LSD
- EG –> crescentic bars west of Abu Qir from rip currents
WIND
- 60% wind comes from W/NW/N. 8% from NE. –> waves move sediment in one direction west to east by LSD
- more deposition (bars, spits, lagoons) on eastern side of delta
- more erosion and less sediment build up on the west

Question 3

physical factors affecting landforms - waves and tides

Answer 3

WAVES
- low energy bc sheltered
- waves mostly come from NW winds
- waves too weak to erode but strong enough to transport and deposit sediment –> bars, spits
- BUT sea levels rising (1.2mm annually) - wave energy reaches further inland –> increases erosion which leads to narrow/ retreat of delta front in future
TIDES
- v low tidal range (microtidal) = not much erosion can occur
- sediment delivered by river isnt regularly washed away –> stays and builds up
- leads to salt marshes & mudflats
(over all tidal currents are weak –> limited offshore sediment transport)

Question 4

physical factors affecting landforms - lithology and structure

Answer 4

LITHOLOGY
1. West of Abu Qir: coarser carbonate sand - from eroded sandstone
- this less mobile - larger, stable bars and beaches
2. Main Nile Delta: finer quartz sand - transported by Nile
- easily moved by winds + currents - spits, dunes + underwater bars

STRUCTURE
- joints/ faults have little impact
- not a structural coastline –> shaped more by process and sediment

Question 5

human factors affecting landforms

Answer 5

1. Aswan High Dam (1964)
   - cut off sediment supply reduced from 120mill tonnes to none.
   - disrupts sediment budget - not enough material to replace what’s lost in wave action –> delta retreating (erosion exceeding deposition)
2. Wetlands drained, lagoons filled, dunes built on, fish farming zones
   - building on dunes removes natural barrier which buffered coast against erosion

Question 6

inter-relationship of landforms - 3 dif zones

Answer 6

1. FORESHORE ZONE: salt marshes, shallow lagoons. these r depositional features formed when river and marine sediment mix. they act as natural flood protection + help biodiversity
2. FRONTAL PLAIN: limestone outcrops + clay deposits. softer material - easily eroded and reshaped by fluvial + marine processes –> allowing sediment accumulation in low energy zones
3. SANDY ZONE - dune fields, sand sheets, hummocks. formed by aeolian (wind blown) transport of dry sediment off delta surface

Question 7

inter-relationship of landforms - examples

Answer 7

• wave action redistributes river sediment by LSD forming curved barrier bars. these close lagoons common on deltas front
• lagoons slowly fill w fine silt and clay during calm weather/ floods. this creates new land - accretion. (but massively disrupted by low sediment supply in nile delta)
• OVERALL INTERCONNECTED BC WHEN SUPPLY REDUCES (DAM) LESS DUNES FORM , LGOON INFILL SLOWS AND BARS ERODE ETC

Question 8

change over time

Answer 8

• before 1964 annual floods deposited silt across delta –> maintained and built up delta
• after Dam: sediment massively reduced and erosion increase –> delta shrinking = sediment starvation
• coastal retreat up to 148m/year - threatens ppl and land use
• sea levels rising 1.2mm/year –> increases inland erosion as wave energy reaches further