How to Reduce Flooding on Your Property Legally

You can usually protect a building from flooding without anyone’s approval beyond building plans, as long as the work is on the building itself and the building is outside the regulated area of a watercourse. Draining your own site is your responsibility, but the water may not be concentrated onto a lower neighbour. Work in a watercourse or its regulated area (clearing the channel, protecting the bank, building a berm, upgrading a crossing) is usually a water use that needs registration or a licence. Any measure that pushes the flood onto someone else can expose you to a claim; approval protects you only if the work was built as approved and with reasonable care.

Want to reduce flood risk on your property? We work out the flood levels you are dealing with, design measures that work, and check they don't push water onto anyone else.

Flood risk assessment

Measures and the approvals they need

Measure	Approval usually needed	Read more
Raise floor levels, thresholds and electrics; flood-resilient finishes; move valuables and equipment up	Building plans where structural work is involved	Freeboard and floor levels
Drain the site to the street, regrade, add swales	Municipal stormwater approval with building plans; no concentrating water onto a lower neighbour	This post
On-site attenuation	Part of the stormwater management plan where the municipality requires one	Attenuation requirements by metro
Keep private drains and pipes clear	None for drains and pipes on your property: it is the owner’s duty	This post
Clear a culvert in a watercourse	A water use; maintaining a private crossing under 4 m wide on the same footprint needs registration under GN 4167	This post
Clear debris, reeds or sediment from the river channel	Often a section 21(c) and (i) water use; moving more than 10 m³ can need environmental authorisation	This post
Bank protection (gabions, riprap, Reno mattresses)	Water use risk matrix and registration, or a licence	Gabions vs Reno mattresses vs riprap
Berm, levee or flood wall	Water use authorisation, municipal consent, possibly environmental authorisation	Berms, levees and flood walls
Upgrade a culvert or crossing on your access road	Water use risk matrix and registration, or a licence	How a road crossing changes the floodline
Emergency repairs after a flood	DWS emergency protocol for work linked to an existing water use; a NEMA section 30A directive for listed activities	Temporary works in rivers

On the building: the simplest gains

A few hundred millimetres of water is enough to ruin floors, walls, electrics and anything stored at ground level. Raising floors, door thresholds and electrical outlets, using finishes that survive wetting, and keeping valuables and equipment off the ground reduce damage without changing how the flood behaves for anyone else. Where the work is structural, it goes through building plans like any other alteration. If the building is inside the regulated area of a watercourse, ask the Department of Water and Sanitation whether the work needs registering under the General Authorisation; building a single residential house there needs registration, though not a risk assessment. A flood risk assessment gives you the flood level to design to; our post on freeboard explains the margin above it.

On your site: drain it, but not onto a neighbour

Stormwater from your roof and paving is your responsibility, but where it goes is limited. Tshwane’s Land Use Scheme says an owner must receive stormwater that naturally drains onto the erf from higher land, but “The Owner of a higher lying Erf may not concentrate the flow of storm water on a lower lying Erf”. Where concentration cannot be prevented and the water cannot be drained to a street, the lower owner must accept it, and the higher owner pays for any pipe or drain needed to carry it. In Pappalardo v Hau (2009) the Supreme Court of Appeal held that an upper owner has no natural right to concentrate flow at a point. It also cited with approval the rule that in town, water should be drained to the street where reasonable measures allow. Our post on whether your development will flood your neighbours covers the law.

Keep what you have working. Cape Town’s Stormwater Management By-law makes owners responsible for maintaining private stormwater systems at their own cost. A blocked pipe or culvert can flood your property even when the river stays in its banks.

In the river: the approvals start

Work in a watercourse or its regulated area is regulated even when it is meant to reduce flooding:

• Clearing the channel. On farms, the Conservation of Agricultural Resources Act requires the land user to remove vegetation in a watercourse “to such an extent that it will not constitute an obstruction during a flood that could cause excessive soil loss”. But removing reeds and sediment alters the bed of the watercourse, which is a section 21(i) water use. De-silting is not on the General Authorisation’s list of activities that need no risk assessment, and moving more than 10 m³ of material can trigger environmental authorisation (activity 19) unless it is done under an approved maintenance management plan. In Johannesburg, clearing within a floodplain also needs a permit from the Johannesburg Roads Agency.
• Bank protection. Gabions and riprap alter the banks. Unless the work is part of an approved river or stormwater management plan, it goes through the General Authorisation’s full process; the notice’s own example is “building of new gabion structures to stop bank erosion”.
• Berms and walls. These impede and divert flow. Our post on berms, levees and flood walls covers when they are legal.
• Crossings. Maintaining a private road or crossing under 4 m wide on the same footprint needs only registration under the General Authorisation. Upgrading or replacing one needs the risk assessment.

Within the regulated area of a watercourse (the 1:100-year floodline or riparian edge, otherwise 100 m from the watercourse, and 500 m around a wetland), the route is the DWS risk matrix completed by a SACNASP-registered professional: Low risk can be registered under the General Authorisation; Medium or High needs a licence.

After a flood

Some emergency repairs can start before the full paperwork, on two conditions. If the repair relates to a water use you are already entitled to, notify the Department of Water and Sanitation’s regional office or the catchment management agency within 24 hours under the emergency protocol in the General Authorisation. If the repair is a listed activity under the environmental regulations, get a section 30A directive from the provincial environment department before starting. The protocol does not cover routine maintenance or poor planning. Our post on temporary works in rivers sets out both processes.

What doesn’t work, or isn’t allowed

• Filling your property in the floodplain can raise flood levels on neighbouring land, and is barred below the 1:50-year line in Cape Town. See filling in a floodplain.
• A wall across a flow path ponds water and sends it round the end.
• Piping your runoff to the boundary concentrates it onto your neighbour.
• Straightening or lining the channel without authorisation is an unauthorised water use, and can send the flood downstream faster.

Start with the numbers

Know the flood level, the depth and the velocity at your property before choosing measures. A flood risk assessment gives you those, tests which measures work, and shows whether they change anything for your neighbours. Measures on a whole catchment are the municipality’s to plan; Cape Town’s stormwater system includes 890 detention ponds.

See our flood risk assessment and drainage design services, or send us the property details.

This post explains the documents listed below. It is not legal advice; requirements change and are applied case by case, so confirm them with the relevant authority before relying on them.