Year 10 Science · Unit 4 · Lesson 7
Apply Worksheet
Learning Goals
Compare three
Complete the table to compare three coastal adaptation strategies. Fill in all blank cells.
| Feature | Sea wall (protect) | Managed retreat | Mangrove restoration |
|---|---|---|---|
| What it involves | |||
| One key advantage | |||
| One key disadvantage |
Real-world context
A small coastal town has 200 houses in a zone projected to be regularly flooded by 2050 due to sea-level rise. The council is weighing three options: (A) build a sea wall for $3 million upfront, which must be raised every 25 years at similar cost; (B) restore a mangrove forest for $500,000 upfront to buffer waves naturally; or (C) implement managed retreat, buying out all 200 properties over 10 years at an average of $300,000 each ($60 million total).
(a) The sea wall is the cheapest upfront option. Explain why scientists describe sea walls as a "treadmill" that may become unsustainable in the long term.
(b) Managed retreat costs the most upfront ($60 million). Give one advantage and one disadvantage of choosing managed retreat for this town.
(c) Which option would you recommend, and why? Refer to at least two factors (e.g. cost over time, community impact, level of protection).
For each action, circle whether it is mainly adaptation or mitigation, then give a one-line reason.
(d) A city paints its rooftops white to reflect sunlight and keep buildings cooler.
(e) A government requires all new cars sold after 2035 to be electric vehicles.
Wrap Up
In one sentence, what was the main idea of this lesson?
Warm Up, Compare three (sample responses)
Sea wall, what it involves: A solid barrier (concrete/rock) built along the shore to block waves and storm surge. Advantage: protects existing infrastructure and can be effective for decades. Disadvantage: expensive to build and maintain, must be raised as seas keep rising, and can worsen erosion at adjacent beaches.
Managed retreat, what it involves: Planned relocation of people and buildings away from high-risk zones, often via buyout schemes over years or decades. Advantage: the most sustainable long-term option where protection costs exceed property values. Disadvantage: politically difficult, costly to buy out properties, and raises property-rights and community-identity concerns.
Mangrove restoration, what it involves: Replanting/restoring mangrove forests that dissipate wave energy and stabilise sediment. Advantage: cost-effective in low-energy coasts, also stores blue carbon and supports fish habitat. Disadvantage: less effective against extreme storm surge and takes years to establish.
Your Turn
(a) As sea levels keep rising, the wall must be raised again and again, each time at major cost. The target keeps moving upward, so spending never stops and eventually exceeds the value of what is protected, hence a "treadmill" that becomes increasingly unsustainable. [2 marks]
(b) Advantage: it permanently removes people from danger and avoids escalating future protection costs (most sustainable long term). Disadvantage: very high upfront cost ($60 million) and significant community disruption, loss of homes and resistance to relocation. [2 marks]
(c) Any reasoned recommendation that weighs at least two factors is acceptable. Example: Managed retreat is best long term because over 50+ years repeated sea-wall raising likely exceeds the buyout cost, and it guarantees safety rather than risking catastrophic wall failure, though the council should phase it gradually and support residents to reduce community impact. Mangroves alone are cheapest but may not protect a built-up town from extreme surge. [3 marks: recommendation + two justified factors]
(d) Adaptation, cool roofs reduce harm from heat that is already occurring; they do not reduce greenhouse gas emissions. (Accept "both" if the student notes reduced air-conditioning use slightly lowers emissions.) [1 mark]
(e) Mitigation, switching to electric vehicles reduces greenhouse gas emissions, addressing the cause of climate change. [1 mark]