Zoning new housing on the flanks of Mount Cameroon
Limbe III is preparing a land-use plan. Mount Cameroon (4,095 m) rises directly behind the town, and eruptions from flank fissures in 1999 and 2000 produced lava flows that cut the Limbe–Idenau road and reached the coast. The planning team has mapped three zones. Zone A lies 2 km from the mapped summit fissure line, on slopes of 18–25°; it is already about 60% built up, holds 4,500 residents and has a single road out. Zone B lies 8 km from the fissure line on a flat 6° coastal shelf, holds 900 residents and is 15 minutes from the main road. Zone C is a 120 ha flat area behind a 40 m ridge, 11 km away, with no road and no piped water. The council can fund one new residential area and one improved evacuation route. Fishing and petty trade are the main livelihoods in A and B. Land in C is held by two families under customary tenure, who want cash. The regional delegation warns that a road into C would cost three times the Zone A route and take two years.
1. Rank Zones A, B and C for new housing. Justify your ranking using the behaviour of lava flows, evacuation time and existing services.
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Distance from the summit is a poor guide on its own; the controlling question is whether a site sits in a valley or on a spur that drains the fissure zone.
Zone A - last. On 18–25° slopes, lava moves fast and warning time is measured in hours or less. The 1999 and 2000 flows followed low ground and cut the only road, so the single exit can be severed before people move. Adding population to a zone that is already 60% built increases exposure and lengthens evacuation, so new housing here creates risk rather than merely occupying it.
Zone B - first, with a condition. The 6° shelf gives slow-moving ground and 15 minutes to the main road, so evacuation is feasible. The condition is a contour check: flows reaching the coast in 1999–2000 travelled along valleys, and if a valley draining the fissure zone opens onto B, the apparent 8 km safety margin disappears. Confirm B is on an interfluve before approving it.
Zone C - second. The ridge may divert a flow, but only if the flow is not funnelled around its end; 11 km gives useful warning. It is downgraded by the missing road and water and by the two-year lead time, not by hazard.
Ranking: B (subject to valley check), C, A.
2. Residents of Zone A say they will rebuild there whatever the plan says. Explain this behaviour and state what it implies for a purely regulatory plan.
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Their position is not irrational. Four things drive it.
Experience. They lived through 1999–2000 and saw the flows stop before reaching their compounds, or saw them take a neighbour's land and not theirs. Direct experience of a near miss usually lowers perceived risk rather than raising it.
Livelihood. Fishing and petty trade depend on beach access and on customers within walking distance. Zone C has neither, so moving is not a house move but a loss of income.
Tenure and cost. Families hold land in A, often without formal title. A plot in a new area means paying for land, a structure and services, while abandoning an asset that may be the household's main store of value.
Trust. Promises of compensation or serviced plots are discounted because previous schemes have stalled.
Implication: a plan that simply prohibits rebuilding will be ignored and will discredit the whole exercise. Regulation works only where a realistic alternative exists - serviced plots at a price people can pay, a school and water point in place before families move, and a transport link that keeps them connected to the beach. Enforcement should concentrate on blocking new subdivisions in A, where refusal costs no one an existing home, while existing residents are given incentives rather than orders.
3. Recommend how the council should spend its two pots of money, and explain the sequence.
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Spend the housing pot on Zone B and the route pot on the Zone A exit, in that order and for different reasons.
Housing pot into B: it is the only zone where new households can be housed without creating new exposure, and it already has 900 residents, so a school, water and a market would serve an existing population as well as newcomers. Before committing, commission the valley check - if a drainage line from the fissure zone opens onto the shelf, B must be dropped and the money redirected to C, accepting the two-year road delay.
Route pot into A: not to open new land but to give 4,500 people a second exit and to keep the coast road usable after a flow. This is the highest-value life-safety spend available, because the single road out is the binding constraint on evacuation.
Sequence: secure the second exit first, since it protects people who are already there and takes months rather than years. Then service B and offer plots. Only then enforce the building freeze in A, so that the prohibition arrives after the alternative exists. Zone C should be surveyed and its customary owners negotiated with now, so it is ready when funds allow rather than being improvised after the next eruption.