1 Flashcards
What factors increase flood risk on low lying and estuarine coastlines?
Height, degree of subsidence, vegetation removal
These factors contribute to the vulnerability of coastlines to flooding.
How does sea level rise affect populations?
Affects a disproportionate number of people due to:
* Dense population in low lying coastlines
* Fertility of low lying deltas for agriculture
* Navigable access in estuaries and deltas for trade
* Support for megacities in river deltas
Examples of megacities include Shanghai, Dhaka, and Karachi.
What does the IPCC predict for coastal populations by 2060?
12% of the world’s population will live in coastal regions less than 10 m above sea level
This prediction highlights the increasing risk of flooding in coastal areas.
What is the height of low lying coastlines above sea level?
1-2 m high above (high tide) sea level
These heights put them at risk from flooding.
What are the flood risks associated with low lying coastlines?
Temporary flood risk from storm surges, permanent flooding from global sea level rise
These risks are critical for planning and disaster management.
What is the highest point in the Maldives?
2.3 m above sea level
The Maldives is particularly vulnerable due to its low elevation.
What is the population of the Maldives?
340,000 spread across 1,200 islands
The population is concentrated in areas at risk of flooding.
What is the main island and capital of the Maldives?
Malé
Malé is protected by a 3 m sea wall.
What percentage of Bangladesh is less than 3 m high above sea level?
60%
Bangladesh’s elevation makes it highly susceptible to flooding.
What is the maximum height above sea level on the island of Tarawa in Kiribati?
3 m
Tarawa is home to most of the Kiribati population.
What causes natural subsidence in low lying coastlines?
Settling and compaction of recently deposited sediment
This process can exacerbate flooding risks.
What is isostatic subsidence in deltas?
Periodic subsidence caused when the weight of delta sediment depresses the crust
This leads to marine transgression and flooding.
What human activities can cause local subsidence?
Drainage of saturated sediment, water abstraction
These activities can worsen flooding conditions.
What is subsidence?
Natural settling and compaction of recently deposited sediment.
What areas are subject to natural subsidence?
Low lying coastlines in estuaries, deltas or outbuilding zones.
How is subsidence usually countered?
By fresh deposition and bioaccretion of organic matter.
What causes periodic isostatic subsidence in deltas?
The weight of delta sediment reaching a threshold that depresses the crust.
What human activities can cause local subsidence?
- Drainage of saturated sediment/soil for agriculture
- Groundwater abstraction
- Weight of cities and built environments
Give an example of an area affected by groundwater abstraction leading to subsidence.
Venice.
What is the impact of land reclaimed from the sea on subsidence?
Subject to subsidence due to water abstraction via evapo-transpiration by agricultural crops.
What is isostatic readjustment?
Adjustment of the Earth’s crust after ice sheet retreat.
How much have large islands in Bangladesh’s Ganges-Brahmaputra delta subsided since 1960?
1.5 m.
What are some causes of subsidence in Bangladesh?
- Isostatic crustal depression
- Water abstraction
- Natural settling of sediment
How does vegetation affect flood risk?
Reduces flood risk by stabilizing sediment and absorbing wave energy.