Low Energy Coastline (Nile Delta) Flashcards
(19 cards)
What is a delta?
It is a depositional landform that forms as rivers empty their water and sediment into another body of water, such as an ocean, lake or other river.
How does a delta form?
- The water slows down near the end of the river, and is able to deposit its sediment, and the single channel breaks into multiple distributaries.
- The coarsest, heaviest material is deposited first, as the river doesn’t have the energy to transport it. The finest, lightest material is carried further downstream, and deposited beyond the river’s mouth, known as alluvium or silt.
How long is the River Nile, and through which countries does it run?
6650km, and it originates in Ethiopia, with tributaries originating in Burundi and Tanzania, flowing through South Sudan, Sudan, and reaching the sea in Egypt.
What are the two parts of a delta called, and how do they vary?
- Sub-aqueous: this part of the delta is underwater. It is the steepest sloping part of the delta, containing the finest silt. The newest part of this sub-aqueous part is the “Prodelta.”
- Sub-aerial: This part of the delta is above water. The area of the sub-aerial delta most affected by winds and waves is called the ‘lower delta,’ and the area most affected by river flow is called the ‘upper delta’’. This sub-aerial portion can be an extension of the river bank, or a series of islands separated by the various distributaries.
How large is the Nile Delta?
22000km2
How long ago did the Nile Delta form?
3000 years.
What is the average discharge of the Nile?
Less than 3000m3/s
What is the average sediment yield and what are the proportions of different sediments in the Nile?
The Nile gets 4.26t/ha/yr of sediment, made up of 30% clay, 40% silt and 30% fine sand.
What 3 subunits can the coastal plain of the delta be divided into?
The foreshore plain, the frontal plain and the sandy zone.
What notable characteristics can be found in the foreshore plain?
It is characterised with elongated ridges, running almost parallel to the current shoreline.
- alternates with lagoons, salt marshes and alluvial deposits in the depressions between them.
What notable characteristics can be found in the frontal plain?
It is located south of the foreshore plain.
- has scattered eroded limestone and clay deposits.
What notable characteristics can be found in the sandy zone?
Composed of a variety of different sand formations:
- sheets, dunes and hummocks.
How far inland does the Nile Delta begin to split into its distributaries?
160km inland.
What effect did the construction of the Aswan Dam in 1964 have on the Nile and its delta?
The delta used to experience annual floods, covering most of the delta in thick silty mud, over 9.6m thick in places.
What is the fetch for waves incident on the Nile Delta coastline?
750km
What direction does the prevailing wind come from?
North Westerly winds.
What coastal landforms have been created as a result of the low fetch, north westerly winds?
The waves have resulted in longshore drift along the coast in an Eastern direction.
- this has resulted in the formation of multiple curved barrier bars.
- These have further resulted in lagoons forming behind them in the form of Lake Burullus, Lake Manzalah, and Lake Edku, all between Abu Qir and Port Said
What has been a negative effect of the Aswan Dam’s construction in 1964?
There has been a rapid reduction in the amount of sediment accreted, from 120 million tonnes/yr to trace amounts today, halting the growth of the delta.
- this has resulted in accelerated erosion rates and rates of coastal retreat as high as 148m/yr.
How do rising sea levels look to affect the Nile Delta?
The Mediterranean rises 1.2mm a year, and this has contributed to accelerated erosion rates
