What Is a Floodline Certificate, and When Does a Municipality Ask for One?

A floodline certificate is an engineer’s signed statement that the floodlines drawn on a plan were determined for the stated flood, usually the 1:100-year flood and often the 1:50-year flood as well. Every township layout needs the 1:100-year floodline under section 144 of the National Water Act, and municipalities extend the requirement to other applications through their land use schemes and planning forms. Who may sign, and how old the line may be, depends on the municipality.

Need a certified floodline for an application? We determine the 1:50 and 1:100-year lines, and our reports are signed by a registered professional engineer.

Floodline determination

Where the requirement comes from

Section 144 of the National Water Act says that “no person may establish a township unless the layout plan shows, in a form acceptable to the local authority concerned, lines indicating the maximum level likely to be reached by floodwaters on average once in every 100 years.” It applies to township establishment everywhere in the country. It does not say who must determine the line or sign for it; the phrase “in a form acceptable to the local authority” leaves that to the municipality.

Municipalities then reach further, through their land use schemes, planning by-laws and application forms. Our guide to every law that applies to a site near a river shows how the floodline fits with the other approvals.

Which applications need one

Municipality	When a certified floodline is required	Source
Every municipality	Township establishment: the 1:100-year floodline on the layout plan	National Water Act, s144
Tshwane	Any application the City specifies: the 1:50 and 1:100-year floodlines on the diagram or layout plan, certified by a professional engineer	Land Use Scheme 2024, cl 18(10)(h)
Ekurhuleni	Township establishment and, where applicable, rezoning	Spatial planning by-law application forms
Polokwane	Building on land likely to flood once in 100 years needs approval, with the floodline on the plans and an engineer’s certificate; township layouts need the 1:50 and 1:100-year lines certified and not more than three years old	Integrated Land Use Scheme 2022, cl 13; Planning By-law, form F-10(A1)
Mbombela	Township layout plans; the 2025/26 user guide adds subdivision, consolidation and farm rezoning, “if applicable”	Spatial Planning and Land Use Management By-law; user guide 2025/26
Msunduzi (Pietermaritzburg)	The 1:50 and 1:100-year lines, determined by a registered professional engineer, where the Municipality asks for them	Single Land Use Scheme 2024, cl 5.43
Nelson Mandela Bay	Land use applications list a “flood line determination and/or report” as a supporting document	Land use application form
Cape Town	Development in the floodplain needs a report by a suitably qualified registered engineering professional; where floodlines have not been determined, the developer appoints one before detailed planning	Floodplain and River Corridor Management Policy 2009

Smaller municipalities that publish no rule, such as Knysna and Sol Plaatje, set requirements case by case. Our city pages cover the local rules in more detail.

Who may sign

There is no national rule. Where a municipality names anyone, it names an engineer:

• Johannesburg: the stormwater by-laws define the floodplain as determined by a professional engineer, meaning a registered professional engineer or technologist approved by the Johannesburg Roads Agency.
• Tshwane, Polokwane and Msunduzi: a registered professional engineer.
• Cape Town: a “suitably qualified registered engineering professional” determines the floodlines and reports on development in the floodplain.

We found no municipality that names a SACNASP-registered scientist for floodlines. SACNASP registration matters for a different document: the risk matrix for a water use authorisation in the regulated area of a watercourse. Our post on who determines a floodline covers what to ask before you appoint anyone.

How old a floodline can be

Polokwane is the only municipality we found with a fixed limit: three years, for township establishment. Elsewhere, a reviewer can still reject a line that no longer reflects the site, for example after new development upstream, a new bridge or a major flood. Our post on why floodlines go out of date lists the causes.

What the certificate should state

Forms differ, but a certificate a reviewer can rely on usually sets out:

• the watercourse and the reach the lines cover;
• the return periods shown (1:100-year, and 1:50-year where asked for);
• the survey or terrain data the model used, and its date;
• whether the lines are drawn to the water surface or the energy level (Cape Town uses the energy level);
• the report that explains the method, and its date;
• the engineer’s name, registration number and signature.

A certificate without the report behind it is weak evidence. Reviewers check the design flood, the model and the assumptions, so the report is what gets the line accepted. Our post on what reviewers check in a floodline study covers that side.

See our floodline determination service, or send us the site and the application type and we will tell you what the municipality is likely to ask for.

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.