Between the 1:50 and 1:100-Year Floodlines: What Each Municipality Allows

No national law bans building below the 1:100-year floodline. Section 144 of the National Water Act only requires the line to be shown on township layout plans. What you may build below it is set by each municipality’s land use scheme, by-laws and policies, and the rules differ widely. Most municipalities with a written rule bar or restrict building below the 1:50-year line and allow development between the 1:50 and 1:100-year lines only on conditions. A few draw the limit at the 1:100-year line itself.

Not sure which line governs your site? We determine the 1:50 and 1:100-year floodlines and show what the municipality's rules mean for your layout.

Floodline determination

Municipality by municipality

Municipality	Below the 1:50-year line	Between the 1:50 and 1:100-year lines	Source
Cape Town	No filling; no formal residential development; no obstruction to flow inside the 20-year line	Conditional for formal housing: floors above the 1:100-year level and basements flood-proofed to the 1:50-year level. Filling and other works need an engineer’s certificate of no material increase in flood hazards for others. No new or existing rights in the high hazard zone at all	Floodplain and River Corridor Management Policy 2009
Johannesburg	No development	No development within the 1:100-year flood area, or the riparian zone plus a buffer of 30, 32 or 50 m, whichever is greater	Land Use Scheme 2018 (2025 review), cl 50(3)(a)
Nelson Mandela Bay	The Municipality may prohibit buildings or set conditions	The Municipality may prohibit buildings or set conditions within the 50- to 100-year floodline	Land Use Scheme 2023, cl 56
George	The City may refuse new permanent residential, commercial or industrial development	Lowest floors above the 100-year flood level “where possible”	Stormwater By-law 2023, s26
Msunduzi (Pietermaritzburg)	No habitable buildings	Ground floors at least 300 mm above the highest flood on record for the land	Single Land Use Scheme 2024, cl 5.43
Mangaung (Bloemfontein)	No building without the Municipality’s consent (in force); no development (draft)	The Municipality may prohibit or restrict use, and permission needs a registered professional engineer’s motivation (draft). On open space and conservation land, no development within the 1:100-year flood area or the riparian zone plus 30 m (draft)	Building Regulations By-law (PN 54 of 2019), s9; draft Land Use Scheme amendment 2025, Floodlines definition and reg 21(2)
Polokwane	No building on land likely to flood once in 100 years without approval	As for the 1:50-year line	Integrated Land Use Scheme 2022, cl 13
Mbombela	No development within the 1:100-year line or a 32 m riparian buffer inside the urban edge (100 m outside) without provincial environmental consent	As for the 1:50-year line; building below the 1:100-year line also needs the City to approve the construction method	Land Use Scheme 2019, cl 6.8.1 and 5.17.2(d)
Stellenbosch	The Municipality may refuse any new permanent residential, commercial or industrial development below the by-law’s “flood line” (the 1:50-year line)	The spatial development framework rules out development below the 1:100-year line on river banks susceptible to flooding	Stormwater By-law 2021; Spatial Development Framework 2019
Tshwane	No explicit ban	No explicit ban; the City can require both lines, certified, on any application it specifies	Land Use Scheme 2024, cl 18(10)(h)

Mines must also comply with GN 704: residue deposits, dams and reservoirs stay outside the 1:100-year line and at least 100 m from any watercourse, and mining outside the 1:50-year line, or 100 m from the watercourse where that is further. Our city pages cover each municipality’s rivers and rules in more detail.

What “conditional” usually means

Where a scheme allows development between the lines on conditions, the conditions usually cover:

• Floor levels above the 1:100-year flood level, often with a margin. Cape Town’s standards ask for at least 250 mm, measured to the energy level. See freeboard and floor levels.
• No harm to others: an engineer showing that the development does not raise flood levels or velocities on neighbouring land. See will my development flood my neighbours?
• No filling without compensation: lost floodplain storage replaced at the same levels. See filling in a floodplain.
• A record on the title: Cape Town’s policy can require a notarial deed of restraint and endorsed building plans.

The national approvals still apply

The municipal rules sit on top of national ones that apply anywhere inside the 1:100-year line. The 1:100-year floodline marks the edge of the regulated area of a watercourse (or the riparian edge, if that is further out). Work inside it that impedes or diverts flow, or alters the bed or banks, is a water use that needs registration or a licence, and the Department treats even a single house there as needing registration. Structures within 32 m of a watercourse can also trigger environmental authorisation. Our post on the four lines that control building near a river explains each line, and permission to build in a floodplain sets out the approvals in order.

Why the band between the lines matters

The 1:50-year flood has a 2% chance of being equalled or exceeded in any year; the 1:100-year flood, a 1% chance. Over a 50-year building life, a building just inside the 1:100-year line has roughly a 40% chance of being reached by that flood at least once. Land between the lines floods less often than land below the 1:50-year line, but it still floods, and the depth and speed of the water decide how dangerous it is. That is why the conditions above focus on floor levels and on not making things worse for anyone else.

See our floodline determination and flood risk assessment services, or send us the site.

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.