Is Your Plot in a Flood Zone? How to Check Flood Risk Before Buying in Mauritius

No single source tells you whether a property in Mauritius floods. The Land Drainage Authority (LDA) is legally required to produce a flood risk map, yet its home page publishes none. Official studies list 305 known flood-prone areas as of September 2021, and what your insurer will pay depends on a contract, not a map. Here are the checks to run, in the order they help.

What the official sources record

The 2017 act that created the LDA gives it the job of inventorying natural and man-made drainage works, producing and updating a flood risk map and a National Land Drainage Plan, and identifying flood risk areas together with the local authorities (section 5). Its home page offers no map and no list of areas, only a phone number (+230 260-3663) and an email address (Secretariat@ldamu.com).

The Land Drainage Master Plan, final version dated 17 May 2022, sets out what was known in September 2021: 224 flood marks and 305 known flood-prone areas. It notes that the National Disaster Risk Reduction and Management Centre (NDRRMC) had already declared some sixty sites critical. In July 2020 the LDA also announced 36 high-risk regions, according to Le Mauricien, among them Vallée-Pitot, Canal Anglais, Cité Richelieu, Baie du Tombeau, Plaine-Magnien, Poste-de-Flacq, Nouvelle-France, Port-Mathurin and Baie-Malgache.

The plan modelled priority sectors in detail: Port Louis (Rivière Lataniers and Canal Anglais, Rivière du Pouce, Ruisseau des Créoles, Canal Dayot), Flic en Flac, Bel Ombre, Nouvelle-France, Grand Baie and Péreybère. It adds supplementary sites, including Pointe aux Sables, Flacq, Terre Rouge, Curepipe downstream and Vacoas–Quatre Bornes. A sector missing from these lists is not necessarily safe, because they name the areas that were studied or declared, not every plot where water collects. The NDRRMC counted some 150 cases of water accumulation and flooding in Mauritius (excluding Rodrigues) in the first quarter of 2018 alone.

Why a plot floods

The Ministry of Environment puts floods down to intense rainfall combined with several factors:

• new buildings and paving that seal the ground and cut infiltration;
• encroachment on the floodplains of watercourses, which reduces their carrying capacity;
• construction on natural drainage paths, on backfilled wetlands or where the water table is high;
• drains that are blocked, silted up or obstructed by service lines;
• building in low-lying areas without adequate drainage.

A plot far from any river can therefore flood if it sits in the path of the water or on old fill, while a raised plot beside a stream may stay dry. The question is not whether there is a river nearby, but where the water goes in a heavy downpour.

Ask the seller and the neighbours

Start with the simplest step. Ask the seller in writing whether the land or house has ever flooded or held standing water, when, and how deep. Then check the answer with two or three neighbours and, if the area is well known, in the local press. This is what the Ministry of Environment guideline asks developers of land subdivisions to do: document a site’s vulnerability from past floods, using the testimony of residents and press reports.

Visit after heavy rain, not in dry weather. Look at where water pools and where it drains, whether the plot lies below the road, whether recent fill has raised the ground, and whether a drain or canal runs alongside and in what state.

Locate the plot against rivers and drains

The Ministry of Local Government’s building permit guide (June 2013) requires construction to stay outside river reserves. The master plan adds that since the Finance Act 2021 the reserve along a natural drainage path is set at 2 metres.

The master plan recommends wider margins along natural drainage paths, from 7 to 10 metres measured from the axis, depending on the area drained, but these remain recommendations. A sworn land surveyor can mark these distances on a plan of the property. If the property is built, look at any drain that crosses or borders it. The 2017 act makes it an offence to damage drainage infrastructure built by the local authorities, the NDU, the RDA or other designated bodies, or to change its course without the LDA’s approval, punishable by a fine of Rs 10,000 to Rs 20,000 and up to twelve months in prison (section 22). A drain that a previous owner diverted or filled in becomes a problem you inherit.

Ask the authorities for the map and their view

Write to the LDA with the address and the title deed references of the plot, and ask whether it lies in a known or modelled flood area. Put the same question to the district council or municipality, which knows where water collects. Keep the replies. A written answer beats a phone call, and it can become the basis for a condition in the promise to sell (see below).

Buying a lot in a subdivision: the drainage study

For subdivisions and other major developments, a Drainage Impact Assessment (DIA) has to form part of the environmental impact assessment. The requirement comes from a 2018-2019 budget measure, and the Ministry of Environment guideline that describes it was issued in 2019. It calls for plans certified by a sworn land surveyor, a map of the catchment, and an analysis of the site’s flood risk and of the project’s effect on neighbouring land. Before you reserve a lot, ask for the DIA and the conditions attached to the subdivision permit. Our guide to buying land in a morcellement covers the other checks.

What the master plan recommends for building in flood-prone areas

The Land Drainage Master Plan makes recommendations for flood-prone areas. New buildings should withstand the depth and speed of the water, the ground floor should sit more than 0.50 m above natural ground, the habitable floor at least 500 mm above the highest 100-year flood, and backfilling should be avoided. It also proposes “No Go” zones, mostly in thinly built areas, where urbanisation would be banned, and “No Expansion” zones in areas already built up, where new construction would be banned except under certain conditions.

These are proposals in a study report. Ask the council what actually applies to the plot, especially if you plan to extend, rebuild or add a floor. For a house that already stands, our article on buying an existing house explains how to check the permits for extensions.

Insurance: check flood cover before you sign

In MUA’s householders multirisk policy, the model published on the MCB website, flood is a peril separate from cyclone. It is defined as the overflowing of natural or artificial watercourses and any flow or accumulation of water on the ground, other than water escaping from supply mains. The policy excludes flood damage to property in the open, to gates, fences, walls and roads, and flood caused by subsidence or landslip.

Another insurer may word it differently. Ask for the definition of flood and the list of exclusions, give the exact address, and get written confirmation that the property is insured on the terms quoted. Our guide to villa insurance in Mauritius sets out what the cover includes, and our page on the cyclone season covers rain risk during cyclones.

Protect yourself in the promise to sell

In Mauritius, a promise to sell signed by both parties counts as a sale, so run these checks before you sign or write them into the promise as a condition precedent. A condition that depends only on your own opinion (“if the land feels safe”) is not valid. One that depends on a third party can be: a written reply from the LDA or the council, if the authority agrees to give one, or a report from an engineer or surveyor you appoint. Set a deadline and say what happens to the deposit if the condition fails. Our article on the promesse de vente and its conditions precedent explains the drafting, which you should do with the notary.

When to walk away

Repeated flooding, a low-lying plot with nowhere for the water to go, recent fill that nobody can account for, a diverted drain, or a building inside a river reserve are all reasons to walk away or renegotiate the price. A property that an insurer will not cover for flood, or covers only with heavy exclusions, can also be hard to resell.

Sources and checks

• Land Drainage Authority: mission and contact details.
• Land Drainage Authority Act 2017 (Act No. 1 of 2017), sections 5 and 22.
• Land Drainage Master Plan, volume 1, final version of 17 May 2022 (Government of Mauritius site, LDA section).
• Drainage Impact Assessment Guideline, Ministry of Environment.
• Building and Land Use Permit Guide, Ministry of Local Government, June 2013.
• MUA, Householders Multirisk Policy Handbook, published by MCB.
• Le Mauricien: “Land Drainage Authority – Risque d’inondation : 36 régions identifiées”, 23 July 2020.