2b- Nile Delta + Flamborough Head Flashcards
Flamborough head location
- North East UK
- salt burn
- borders North Sea
FH- Physical factor - Wind + waves
Fetch = from NNW, 1500km over stormy North Sea
Waves= average >4m
FH- Physical factor - tides
- macro tidal range (large) = 4m
- due to UK bring on continental shelf so surrounded by shallower ocean
- wave cut notches more significant = more of cliff impacted = faster cliff retreat
FH- Physical factor - geology
- disconcordant coastline
- bays + headlands form
weaker clays + Shales = 0.8m a year
stronger chalk + Limestone = 0.1m a year
What direction is sediment carried at FB ( think prevailing wind)
North to south
NNW prevailing wind
Where is the source of most sediment at FB
90% from cliff erosion
What is the orientation of FB cost + why is this significant
- salt burn faces NW = faces waves head on = high rates of erosion
Major landforms at FB
Filey brigg = headland
Filey bay = bay sheltered by Filey brig
Robin hoods bay
How might landforms change over time at FB
1- bays become wider as waves refract around headland
2- cliffs retreat = retreating coastline
3- caves become arches ect
4- slumping of soft rocks= sloping profile
5- rising sea level allows waves to reach high = erosion will continue despite increasing WCPs
Inter-relationship of landforms FB
1- erosion of bays creates headlands = allows caves + other landforms to form
2- waves refract + lose energy on headland = sheltered areas in bays have deposition = beaches
3- erosion of cliffs = forms WCP + provides sediment for beaches
Location of Nile delta
- Northern Egypt/ Africa
- borders Mediterranean
ND- Physical factor - Wind
- prevailing wind = NW over calm Mediterranean
-fetch = 750km
ND- Physical factor - waves
- average wave height = 0.94 , very low energy
- occasional summer storm = 4m wave
ND- Physical factor - geology
- concordant coastline
-weak Lithology + structure = silts + sands - occasional limestone outcrop (Alexandria)
- easily eroded
ND- Physical factor -Tides
- small tidal range = 0.5m
- Mediterranean is a small enclosed sea = little water to be pulled into tidal bulge
- less range for erosion
ND- Physical factor - Sediment supply
- large fluvial sediment input = 120 million tonnes/ year
- 90% sediment budget = fluvial
- Silts + sands mainly = theoretically easily eroded
What has recently affected the sediment budget and how had this affected the coastline- ND
- Aswan dam 1964
- drastically reduced sediment supply
- coastline retreating up to 148m/year
Nile delta before human impact
-Deposition has exceeded erosion for past 3000 years
- building of Aswan dam has caused retreat showing human impact on landscapes
Key landforms Nile delta
- limestone headland at Alexandria
- manzala bar + manzala lake behind
- Damietta + Rosetta promontories
What is a delta
Large areas of sediment build up at river mouths
What is flocculation
1- Occors when salt and freshwater meet
2- causes clumping of sediment = when sediment gets big enough it is deposited/ dropped as it is too much energy to carry
Interrelationships at Nile delta
1- promontory’s (at distributaries mouth) are build up of sediment= supply’s sediment for LSD eastwards= manzala bar produced (50km long)
2- promontory’s shelter coast = encourage deposition
3- Alexandria headland shelters Abu-Qir bay = beach
4- manzala bar shelters area behind = salt marsh
5- waves arriving parralel to Abu-Qir bay = rip currents= offshore bars
How might Nile delta change over time
- coastline retreats due to decreased sediment budget
- burrulus spit breached = had been a bar
How do rip currents form ( Abu Qir bay)
- waves arrive parallel to coast
- backwash cannot flow off beach due to too much incoming swash = backwash is forced to concentrate on one area
= strong outgoing current / rip current - offshore bars form due to backwash losing energy and depositing sediment
How might warmer climate affect FH
- more chemical weathering = coastline retreats faster
- chance for coastal flooding + formation of submergent landforms
How might warmer climate affect Nile delta
- excessive coastal flooding due to very flat land eg: Alexandria would submerge after 50cm rise
- more water in Nile = more fluvial sediment = more deposition
How much are sea levels rising a year in Mediterranean
1.2 mm a year
Less than global due to being a enclosed sea
How much would sea levels need to rise to submerge Alexandria - ND
0.5m / 50cm
how tall are cliffs at Flamborough head
120m
- Cliff collapse provides significant sediment
direction of LSD at ND
West to East
how could a Flood plain and river valley form before sea level change for Rias
-Rivers erode sediment from their banks and bedrock as they flow downstream towards the sea.
-The riverbed deepens over time. As rivers move from side to side, they gradually erode the valley, creating broad plains.
-As a river floods, it overflows its bank. The flood carries sediment out over the land. After the water withdraws, the sediment remains. If a river floods repeatedly, over time this sediment will build up into a flood plain