Rivers and coasts case studies Flashcards
What are some examples of sea level change?
- Raised beaches and fossil cliffs in Scotland. Fjord and Clyde valleys raise 2mm annually
- Kingsbridge estuary, Devon, 6 m long ria. Main channel is 1 m wide near its mouth at Salcombe. Two large drowned tributaries extend from the east side of the ria, with Frogmore Creek 2 km long and 500 m wide.
- Norwegian fjords, Sognefjord in western Norway is 205 km long, 1.3 deep and the main branch is 4.5 km wide.
- Dalmatian Coast, Croatia
The Dalmatian region of Croatia has a limestone coastline stretching 520 km NW-SE with 1,240 islands running parallel to the coast.
Why is Holderness a point of interest?
- The Holderness coast is the fastest eroding coastline in europe, it extends 61 km from flamborough in the north to spurn point in the south. Located on the east coast of england.
How fast is Holderness eroding?
It is eroding at an average of 2m per year and this is around 2 million tonnes of material each year. Around 3 miles of land has been lost since roman times. This includes losing 23 towns and villages due to the erosion of the coastline.
Why is Holderness coast eroding so fast?
- The underlying geology of Holderness coastline is bedrock and chalk however the majority of the coastline is made up of boulder clay which can be eroded very easily due to it being a sedimentary rock type.
- Another reason why the coastline is eroding so quickly is due to the constant strong prevailing wind which drives longshore drift and moves large amounts of material south of the coastline.
What erosional landforms can was see on Holderness coast?
- On this coastline we can see textbook erosion and deposition and therefore can be used as a great example, We can see examples of erosion through caves, stacks and arches. We can also see what longshore drift can also create through spurn point.
Why is dorset vulnerable to erosion?
- The lithology of the area, weaker rock that is more vulnerable to hydraulic action and abrasion erosion will cause for quicker coastal recession. Eg- bands of clay on the Jurassic coastline
- The type of coastline. The dorset coastline is discordant, meaning that it has bands of rock that run parallel. This means that rock type varies, with different rock characteristics, there is different rates of coastal erosion.
- The waves and climate. Dorset lies on the south west of the UK’s coastline and is vulnerable to the effects from powerful storms and crashing waves from the atlantic ocean, this causes for increased rates of coastal recession due to more powerful waves (increased erosion)(rapid recession)
- Weathering. Dorset is vulnerable to all forms of weathering, this causes for cliff sides and land to be destroyed and stripped away,which causes for coastal recession and puts stakeholders and the public in danger as their property and land can be at risk.
- Poor rock structure- if rocks have faulty joints (caused by weathering or potentially tectonic processes) then it can affect the entire structural integrity of the land, which causes for coastal recession as land is taken away from the mainland due to naturally occurring processes.
Where is the Nile delta?
- Located in Northern Egypt where the river Nile meets the Mediterranean sea, a depositional landform created by sediment deposited by the Nile, since the Aswan high Dam was built in the 1960s the river and surrounding areas have been affected drastically.
How has the river discharge of the nile delta been affected by the aswan high dam?
- River discharge fell from 35 billion m^3 to 10 billion m^3 per year,
- sediment fell from 130 million tonnes to 15 million tonnes per year
How has the erosion rate of the rosetta been affected by the aswan high dam?
- The erosion rate at the Rosetta jumped from 25m per year to 200m per year, due to starvation of sediment at the delta (Rosetta - main delta branch meets the sea)
How has the Aswan high dam affected deposition and erosion?
Changes caused by: water withdrawals for industry, cities and farming from the Lake Nasser reservoir, sediment being trapped by the dam meaning water travels slowly causing sediment to be deposited early.
How has the akasombo dam reduced flow of sediment?
- Akosombo Dam in Ghana also reduced flow of sediment, to the river volta, from 70 million m^3 a year to 7 million m^3 a year. Keta, ghana has an erosion rate of 8m/year meaning the coastal road leading to Tongo was lost.
What are the human flood risk factors in Bangladesh?
-The removal of coastal forest mangroves leads to increased flooding as the protective vegetation barrier has been removed so cannot take the impact of the storm surges.
-Bangladesh contains the 180km Sundarbans (largest mangrove forest in the world). -However, 71% is experiencing some vegetation removal. Some parts are eroding at 200m p.a
What are the physical flood risk factors of Bangladesh?
- Bangladesh suffers from sudden heavy rainstorms and has many large river located nearby, this leads to the overflow of the rivers in the monsoon months causing major flooding
- Most of the country is a very low lying river delta only 1-3 metres above sea level so suffers with seal evel rise and heavy rain as well as storm surges and flooding
- There are three major rivers in Bangladesh such as the gangees that carry the snowmelt from the himilayas overloading the capacity of the rivers
How will sea level change affect Bangladesh?
- 40cm sea level rise would permanently submerge 11% of Bangladesh, creating 7-10 million environmental refugees.
- Sea levels will rise by 55cm by 2100 according to the IPCC.
What were the physical characteristics pf cyclone sidr?
- The cyclone being a category 4 brought along 240 kph winds and tidal waves up to 5m high and storm surges up to 6m.
What were the social impacts of cyclone sidr?
- 15,000 with 1,001 still missing.
- Vast areas of Bangladesh are flooded by theses storm surges, forcing millions of people from their homes and farms in densely populated coastal areas.
What were the infrastructural impacts of cyclone sidr?
- Due to the destruction caused by the high winds and strong waters roads were unusable, all electricity was cut off so no one had any power, and water sources were contaminated with debris.
What made cyclone sidr so destructive?
- 2/3s of Bangladesh land is below 5m above sea level. The triangular shape of the Bay of Bengal concentrates a cyclone storm surge as it moves North, increasing its height as it makes landfall. - The deforestation of coastal mangrove forests has removed vegetation that once stabilised coastal swamps and dissipated wave energy during tropical cyclones.
