Coasts and People: Opportunities, Hazards and Sustainable Management - Part 2

Coastal erosion. Storm waves erode cliffs and shorelines. UK east coast (Holderness) loses ~2m/year. Properties, roads, farmland lost.

Storm surges. Low atmospheric pressure + strong winds raise local sea level. Storm waves flood coastlines. Examples: 1953 North Sea Flood (>2,000 dead UK + Netherlands), Hurricane Katrina (2005, USA, >1,800 dead).

Tsunamis. Underwater EARTHQUAKES, landslides, or volcanic eruptions displace the seabed → giant low-amplitude waves in deep ocean → grow huge (up to 30m) on reaching shore.

• 2004 Indian Ocean tsunami: ~230,000 dead across 14 countries.
• 2011 Tōhoku, Japan: ~20,000 dead; Fukushima nuclear disaster.

Sea-level rise. Climate-change driven. Causes: THERMAL EXPANSION of warming oceans (~50%) and MELTING ice from Greenland, Antarctica, glaciers.

• Threatens low-lying coasts: Bangladesh, Maldives, Pacific islands, Florida.
• Already displaced first 'climate refugees'.

Cambridge tip. Mark scheme rewards SPECIFIC examples with figures.

Trigger. Most commonly an UNDERWATER EARTHQUAKE at a subduction zone. Also landslides, volcanic eruptions.

Mechanism.

1. Seabed displaces vertically.
2. Water column lifted (or dropped) above.
3. Waves spread outward with long wavelength (~100 km) and low height in deep ocean (~1m).
4. Approaching shallow water, wave HEIGHT GROWS as energy compresses. Heights of 10-30m at the shore are common; 40m+ have been recorded.

Impact.

• Massive loss of life (drowning, building collapse).
• Total destruction of coastal infrastructure.
• Long-term contamination (debris, salt water inland).

Examples. 2004 Indian Ocean (~230,000 dead), 2011 Tōhoku (~20,000 dead + Fukushima nuclear disaster).

Cambridge tip. Don't call tsunamis 'tidal waves' — they have nothing to do with tides.

Causes.

• THERMAL EXPANSION — warming oceans expand (~50% of observed rise).
• ICE MELT — Greenland, Antarctica, glaciers.

Rate. Current rise ~3-4 mm/year. Accelerating.

Consequences.

• Coastal flooding of low-lying land (Bangladesh, Florida, Maldives).
• Salinisation — salt water intrudes into freshwater aquifers and farmland.
• Displacement of millions. Maldives, Tuvalu, Kiribati face national disappearance.
• Loss of coastal ecosystems (salt marshes squeezed between rising seas and sea walls — 'coastal squeeze').
• Storm surges become more damaging on top of higher baseline.

Cambridge tip. Both CAUSES matter — don't skip thermal expansion.