Engineering Geology and Geohazards Lecture 16 & 17: Climate Change, flooding, Storm surges Flashcards
Describe how climate change is increasing storm hazards
- Increased storminess (higher river discharges)
- Increase in storm surge frequency and intensity
- Increase in sea level
Warmer water expands….sea level rising
* Melting of polar ice caps
- increased solar heating…faster ice melt…
- continental ice further raises sea level
* Melting of tropical glaciers (Andes, Himalaya)
- flooding from meltwater lakes
* Bigger temperature contrast between Polar
& Equatorial ocean water
- energy source for tropical storms
- record number of severe hurricanes
Describe Hurricane Stan
Hurricane Stan -
landfall 04/10/05
Mostly a Tropical Storm.
Hit a poor country, Guatemala: more deaths than Katrina .
- Heavy rains triggered ca. 900 landslides / flows
- Many village areas declared mass graves
- 1000’s of fatalities in the region
- Exacerbated by regional poverty: deforestation
& lack of urban planning controls
Describe Recent UK deformation events/ Isostatic change
Crustal uplift in Scotland (glacial
rebound) = falling sea level
Crustal subsidence in England & Wales = rising sea level
Describe how the Thames Estruary is protected
Thames Barrier completed in 1983:
- designed for 1 in 1000 yr flood
- ie, a flood of c. 6m amsl
Estuary now protected by 370 km of modern flood walls, plus 36 barriers
Cost: c. £1 B
Barrier has been closed 221 times as of 16th April 2024
Describe the Second Thames dam
A new, larger barrier is now being planned,
located down-river and operating from 2030
§ Plan: outer barrier complex, 10 km long and
stretching from Sheerness across to Southend.
By 2030, due to global warming, our 1 in 1000
yr flood will be 1 in 500 yr event
§ The 1 in 1000 yr flood of 2030 would top the
current Barrier and floodwalls
Describe the floods in the UK of 2007
- 13 dead
- 48,000 houses
- 7,300 businesses
- 350,000 without water
- > £6 Bn losses
- 3-day warning, but some flood models failed
- Disruption of critical facilities – and livelihoods
Describe the Pitt review
UK Climate Change: planning ahead
The Pitt Review (2008)
- what were the main recommendations ?
* 25-year plan for flooding, with a dedicated Cabinet
committee
* overhaul of building regulations for floodplain homes:
appropriate construction & SUDS (Sustainable Urban
Drainage Systems)
* building on floodplains will be an
“absolute exception“
* joint flood command centre: Met Office
+ Env Agency
Define a storm surge
A rise in sea level caused by low atmospheric pressure and the accumulation of water driven towards shore by storm winds.
strong winds pile water against coast, especially within embayments open to large fetch.
- low pressure further elevates sea surface. Sea level rises 1cm for every 1 mb fall in pressure, eg., 960 mb depression = 50 cm rise in sea level.
- disastrous if surge affects low-lying coastline and coincides
with high Spring tides and large swell.
A UK problem, The Solent and English Channel, Bristol Channel and the North Sea.
Especially severe when combined with Spring tides.
Describe England and Wales flood defences
England and Wales flood defences
~40,000 km
Cities most at risk:
* Hull
* Cardiff
* Portsmouth
* Thames Gateway
Counties most at risk
- Lincolnshire
- Norfolk
- Suffolk
- Essex
- Kent
Name the two areas of the UK coast most susceptible to Storm surges
The Southern/Jurassic coast from the Atlantic ocean
Holderness coast, East Anglia/Norfolk /Suffolk/ Lincolnshire/ West coast
Define Amphidromic circulation and Amphidromic points
Tidal bulge entering an ocean basin is deflected to the right, in the Northern Hemisphere, by the Coriolis effect. This creates a swirling amphidromic circulation centred on an amphidromic point, where sea level remains unchanged.
Amphidromic points are locations where there are little or no tide in the ocean.
(This is also related to influence of continental land masses interfering with the westward movement of tidal bulges and the influence of the Coriolis effect.)
Where are the two amphidromic points around the UK
Ampidromic points in the N
Sea and English Channel.
Describe the 1953 North sea storm surge
The 1953 North Sea storm surge
- 31 Jan / 1 Feb: hurricane-force winds
- Fetch = c. 2,000 km / storm waves > 6m
- UK: >400 killed; 32,000 evacuated
- ~1,000 km2 of farmland flooded
- Greatest natural disaster to affect UK
- Cost: equivalent to £5 billion today
- ~2,000 km of coastline affected
- Highest recorded sea level for North Sea
- 1 in 250 year event
Describe the 1953 storm surge impact on the Netherlands
- 1,835 killed
- 4,500 buildings destroyed
- 70,000 evacuated
- 10,000 animals drowned
- 12% of farmland flooded
- Estimated cost ~£300 million
- 3 million inhabitants of South Holland saved
by ramming a ship into a breach in their last
intact sea dyke
