Coasts - Case Study - Nile Delta - Low Energy Coastline Flashcards
How long is the River Nile?
- 6650km
What is the River Nile’s catchment area?
More than 3 million km(2)
How does the River Nile influence the formation of landforms? (2)
- Huge sediment load (sediment budget) = 30% clay, 40% silt & 30% fine sand
- Average annual sediment yield = 4.26 tonnes/ha/year (total = 91.3 million tonnes per year for the whole Blue Nile Basin in Ethiopia)
What are the 3 distinct sub-units of the coastal plain & their characteristics? (3)
- Foreshore plain- elongated ridges alternating with lagoons, salt marshes and alluvial deposits the depressions between them
- Frontal plain (south of foreshore plain)- scattered eroded limestone outcrops and clay deposits
- Sandy zone- variety of different sand formations (i.e. sheets, dunes, hummocks)
What are the two distributaries of the Nile Delta?
- Rosetta
- Damietta
How does wave action influence the delta?
- Wave action in the Mediterranean redistributes the sediment at the front of the delta
- The reworked sediment forms a series of curved barrier bars- close off segments of the Med Sea to form lagoons (turn into form of sub-environment & soon become filled with fine sediment)
- Low wave energy (low tidal range due to small entrance to Med - 2cm/year & small fetch) mean little erosion
What are the estimated surface current velocities at different times in the year? (4)
- 9.26-13.5 cm/s during summer
- 4.46 cm/s during autumn
- 23.14 cm/s during winter (strong winds
- 8.4 cm/s during calm spring weather
How does seabed topography influence the delta? (2)
- Shallow continental shelf = friction so waves lose energy (deposition greater than erosion)
- Provides surface for accretion
What is the prevailing wind & therefore wave direction? (2)
- NW winds = waves coming from west, NW, N (55-60% of time)
- Waves come from NE (8% of time)
Which physical factor is most important in influencing the delta?
- Large scale factors (i.e. seabed topography, sediment budget) most important in influencing the delta over millennia, but on a smaller, more local, scale other physical factors (i.e. winds, waves) influence the movement of sediment over time along the coastline.
What are the landforms east & west of Abu Qir headland? (2)
. Beaches west contain long crescentic bar systems (associated with rip currents and negligible LSD)
- Parellel longshore bars exist along delta extending from east of Abu Qir to Port Said (created by dominant eastward longshore current & associated LSD of sediment)
- Manzala lagoon at Port Said (East)
When was the Aswan High Dam built?
- 1964
How has the building of the dam influenced the delta? (3)
- Imbalance created between erosion and accretion
- Rapid reduction in amount of sediment accreted (120m tonnes/year to only trace amounts today)
- Changes along NW Nile Delta with accelerated erosion & rates of coastal retreat as high as 148m/year
What has also contributed to higher erosion rates? (2)
- Rising sea levels in Med (1.2mm/year)
- Higher erosion rates as deeper water = large waves with higher amounts of energy (reach further inland)
