Rivers and People: Opportunities, Hazards, and Management - Part 2

Question

Step-by-step solution

1. Step 1

   Social impact (1 mark). A consequence for PEOPLE and society — e.g. people are killed or drowned, families are made homeless / displaced, or waterborne disease (cholera) spreads as supplies are contaminated.

2. Step 2

   Economic impact (1 mark). A consequence for MONEY, jobs or property — e.g. homes and businesses are damaged, crops in fields are destroyed, or roads and bridges need expensive repair.

3. Step 3

   Environmental impact (1 mark). A consequence for ECOSYSTEMS — e.g. habitats are destroyed, the river is polluted by sewage and chemicals washed into it, or fertile silt is deposited on the floodplain (a positive one).

Question

Step-by-step solution

1. Step 1

   Hard engineering (2 marks). Building physical structures to control the river — e.g. dams and reservoirs (store water and release it slowly), embankments / levées (raised banks that hold more water in the channel), channel straightening or flood walls.

2. Step 2

   Soft engineering (2 marks). Working WITH natural processes rather than against them — e.g. afforestation (planting trees to intercept rain and slow runoff), floodplain zoning (planning rules on land use), washlands / flood storage, river restoration or flood-warning systems.

Question

Step-by-step solution

1. Step 1

   Social — loss of life and displacement (2 marks). Floodwater drowns people and sweeps away homes, so families are killed or made homeless and forced into temporary shelters. This causes lasting trauma and breaks up communities.

2. Step 2

   Social — disease (1 mark). Floodwater mixes with sewage and contaminates drinking-water supplies, so waterborne diseases such as cholera and dysentery spread, especially in poorer countries with weak sanitation.

3. Step 3

   Economic — property and infrastructure (2 marks). Homes, shops and factories are damaged and their contents ruined, so owners face huge repair bills and businesses lose trade; roads, bridges and railways are washed out, cutting off supplies and raising the cost of recovery.

4. Step 4

   Economic — agriculture and insurance (1 mark). Crops drown and livestock are lost, reducing farm income, while insurance premiums rise for everyone in flood-prone areas.

Question

Step-by-step solution

1. Step 1

   Advantage — flood control (2 marks). A dam holds back river water in a reservoir, so discharge downstream can be released slowly and evenly. This lowers the peak flow during storms, so settlements downstream are protected from flooding.

2. Step 2

   Advantage — multi-purpose benefits (1 mark). Reservoirs also store water for drinking and irrigation and can generate hydro-electric power, so the scheme provides resources as well as flood protection.

3. Step 3

   Disadvantage — cost and displacement (2 marks). Dams are very expensive to build, so they are hard for poorer countries to afford; the reservoir floods land upstream, so farmland and villages are lost and people must be relocated.

4. Step 4

   Disadvantage — environmental effects (1 mark). The dam traps sediment, so fertile silt no longer reaches the floodplain downstream and the river bed below the dam can erode; fish migration is also blocked.

Question

Step-by-step solution

1. Step 1

   Choose a real detailed specific example. The River Thames, England is well documented. After the 1953 North Sea storm surge, the Thames Barrier (opened 1984) was built to protect London, supported by raised embankments and floodplain washlands upstream.

2. Step 2

   Successes (hard engineering). The Thames Barrier has closed safely hundreds of times and has protected central London — homes, the Underground and businesses worth billions — from tidal and fluvial flooding. This is a clear, measurable success of hard engineering.

3. Step 3

   Successes (soft engineering). Upstream, schemes use natural floodplain storage and floodplain zoning to hold water back, and the Environment Agency's flood-warning system gives residents time to act, reducing deaths and losses.

4. Step 4

   Limitations. The Barrier was very costly (over £500 million) and is closing more often as sea levels rise, so its lifespan is finite and a costly replacement is being planned. Building on the floodplain has continued, increasing the value at risk.

5. Step 5

   Judgement. Overall the management has been largely successful in protecting a high-value capital city, but it depends on continued expensive upgrades; combining hard defences with soft measures (warning, zoning, storage) has been more effective than either alone.

Question

Step-by-step solution

1. Step 1

   Case for soft engineering. Afforestation, washlands and river restoration work WITH nature: they are cheaper, create habitats, and avoid the silt-trapping and channel-erosion problems of dams. Floodplain zoning prevents building in high-risk areas, reducing the value at risk long term — so soft approaches are more environmentally and financially sustainable.

2. Step 2

   Limits of soft engineering. Soft measures cannot fully protect large existing cities already built on floodplains, and they rely on people changing behaviour. Afforestation takes decades to be effective, so it offers little protection in the short term.

3. Step 3

   Case for hard engineering. For a dense, high-value city, hard defences give reliable, immediate protection — e.g. the Thames Barrier has shielded London since 1984. Where lives and billions of pounds are at risk, the engineering cost is justified.

4. Step 4

   Drawbacks of hard engineering. It is expensive, displaces people (dams flood land upstream), traps sediment and damages ecosystems, and can give a false sense of security that encourages risky floodplain development.

5. Step 5

   Judgement. I largely agree that soft engineering is more SUSTAINABLE, but it is not always sufficient. The best strategy is integrated management — soft measures (zoning, afforestation, warnings, washlands) wherever possible, with hard defences only where high-value areas demand them, as on the Thames.