2.10 - Guinea's Coastline Flashcards
Effects Of Rock Hardness On Coastline
Softer and uncemented sediment/rock are vulnerable to cliff retreat. Igneous have a stronger crystalline structure where joints and fractures in the rock create a complex coastline.
Geological Orientation
Discordant coasts have different rates of erosion, resulting in headlands and bays. Headlands concentrate wave energy (refraction) resulting in more complex erosion features.
Wave Type/Energy
Water is driven into cracks in rocks, compressing air that is already there, creating an explosive blast. Bombardment and blasting is made worse by sediment chucked at the coast.
Rock Breakdown/Erosion
e.g. hydraulic acction/attrition/abrasion, often together with other subaerial. Some mechanical processes expose the coastline to wave and subaerial processes.
Rock Layers
Differences within the cliff face affects level of resistance, different rates of erosion and overtime cause landslides.
Wave-Cut Erosion
Eroded cliffs leave a wave-cut platofrm, which can be covered by low tide, leading to abrasion. Abrasion and limestone solution creating a rocky foreshore.
West Africa
700m of erosion in 40 years particularly in NW Guinea
10 cm of SLR since 1950, 1m by 2100.
Urbanisation is high along the coast - fishing, tourism and commerce.
SLR Coastal Recession
Waves tend further up the beaches and cliffs. This affects coasts made of soft sediments.
Swell Waves Coastal Recession
Stormy monsoon months. Wave heights of 3m and 3.8m damage leading to unemployment for Kenyan workers.
Swell Waves
Waves that come from different area to where they were generated.
Mangrove Deforestation Coastal Recession
Less mangroves absorb less wave energy. Mangroves are used for the wood to cook fish, they are also used as supply.
Diamond Mining Coastal Recession
Gravel extraction from rivers, where diamonds are retrieved. Gravel and sediment is not always being returned.
Sand Extraction Coastal Recession
It’s removed from the river for housing, meaning sediment isn’t transported to the coastline, and therefore there’s increased vulnerability to coastal recession.
Coastal Management/Dredging
Removal of materials for ports and beach nourishment. Deep water, energy is retained. Destroy marine habitats, disrupt functioning food chains and damage environmental habitats.
Sea Defence Vs Mangrove Deforestation
These fators counteract one another, as you need defences to counter impacts of removing mangroves.
Expensive Coast Management Vs Offshore Dredging
IN order to counter the removal of material you need coastal expensive coastal management.
Diamond Mining Vs Strong Waves
Strong waves increase the possibility of coastal recession, it becomes easier to mine into the diamonds as a result.
Offshore Dredging Vs Strong Waves
Removing material increases the imapct of the strong waves more wave energy, so more erosion.
SLR vs Mangrove Deforestation
Removed the physical barrier, allowing the sea level to have a larger impact.
Offshore Dredging Vs Mangrove Defrestation
Offshore dredging nourishes the land but increases impact of wave energy. Mangrove deforestation means less wave energy is absorbed.
Coastlines Can Recover From Human Activity
Mappleton Coastal Managemnt scheme - 2 million spent
Hard Engineering - Norwegian granite rich armour at base.
Two rock groynes to stop material from moving along
Erosion has decreased and cliff risk has reduced.
Coastlines Can’t Recover From Human Activity
Alexandra Flooding, 7 million displaced, sea defences didn’t work, farming industries cost.
Recreation and tourism makes up 70% of tourism in T&T.
Coastal management is only effective if the coastal processes stay the same.
Climate change humans move them over time.
