The golf course is doing a job you cannot see: it is holding back the flood

There is a reason this land has never been built on. It is the lowest ground in the valley, where three rivers meet, and one of the last open spaces that still soaks up winter rain before it reaches homes. Pave it and the water goes somewhere. Every flood fact in this article comes from the City's own consultants or the City's own climate spending, not our opinion.

Where does the water come from?

Start with the word catchment. A catchment is simply the bowl of land that drains to a single point. Think of it as a bathtub: whatever rain falls anywhere in the bowl runs toward the lowest drain. Gravity decides where that is.

The King David Mowbray Golf Course sits at the drain. It lies in the Salt River catchment, whose three major river systems are the Liesbeeck, the Black and the Elsieskraal. The Elsieskraal comes in from the Tygerberg Hills to the north-east and joins the Black River, which runs through the low ground just south of Pinelands toward the sea, where it meets the Liesbeeck and continues as the Salt River. The Vygekraal is present on the site itself as floodplain wetlands. The golf course occupies the flat floodplain where these systems meet and slow down.

The map below shows the real river geometry, drawn from OpenStreetMap data. The grey dashed lines are the sections of the Elsieskraal that were canalised decades ago (more on that below). The blue lines are the natural channels. The green polygon is the golf course itself.

What is a floodplain, and why does it matter?

A floodplain is the flat, low land alongside a river that the river is meant to spill onto when it fills up. Think of it as the river's overflow car park. When heavy rain falls, the water has to go somewhere. If a floodplain is there, the river spreads out slowly across soft ground, soaks in, and drains away over hours or days.

That soaking function is the key. Soft, vegetated ground acts like a sponge. It absorbs rain, slows it down, spreads it sideways, and releases it gently. What comes out the other end is a trickle, not a surge. That is real, invisible flood protection for the homes and roads downstream.

That protection only works while the ground is open and soft. It does not work once you have covered it in roofs, roads, and paving.

The history that makes this site important

In the 1970s, roughly two-thirds of the Elsieskraal River was canalised. That means it was straightened and lined with concrete to make it move water faster and stop it flooding the surrounding land. You can see those stretches on the map above as dashed grey lines.

The problem with concrete channels is that they do exactly what they promise: they move water faster. A natural river meanders, slows, spreads, and soaks. A concrete canal rushes. In heavy rain, that speed is what turns a flood into a dangerous surge. Fast water has killed people in Cape Town's urbanised drainage channels in past floods.

So when most of the river was canalised, the catchment lost most of its natural sponge. The water that used to soak into the riverbank and floodplain now races downstream. That makes every remaining open, soft, low-lying piece of land in the catchment more valuable, not less, as a place where water can still slow down. The golf course is one of the largest of those remaining pieces. It is doing work that the river can no longer do for itself.

What happens if you build on it?

Roofs, roads, car parks and paving do not soak up rain. Water hits them and runs off immediately. It flows into the stormwater network and then into the river and canal all at once, as a surge rather than a trickle. The more of a catchment you cover in hard surfaces, the faster and higher the flood peaks downstream.

Downstream from the golf course is Pinelands and Maitland.

This is not an inference we are making. The City's own environmental consultants wrote it in the assessment for this development:

That sentence is in the City's own documents. The consultants accept, in writing, that this floodplain provides flood protection in an already-hardened catchment. What happens when you add still more hard surface to that catchment is not a quote from them but basic hydrology, which the rest of this article sets out. The disposal process continues regardless.

But they will not build in the river itself

A common response to flood risk concerns is that the development will respect flood lines and setback zones, so no buildings will sit in the active river channel. That is true as far as it goes, but it misses the point.

The danger is not buildings in the river. The danger is hardening the land around and above the floodplain. Rain that falls on the new roofs, roads and car parks of a development with up to ~6,700 homes and 75,000 square metres of commercial space does not soak into the ground. It runs off fast. It reaches the Elsieskraal canal and the Black River faster and in greater volume than before, regardless of where the buildings themselves sit relative to the flood line. The flood line is drawn around the river's current behaviour; it is not drawn around the behaviour of a river whose entire upper catchment has just been paved.

There is also a second problem with flood lines. They are drawn on historical rainfall data. As storms get more intense and more frequent, a flood line drawn on past records understates the risk ahead. The City's own Climate Change Action Plan acknowledges this, warning of more severe rainfall events as the climate shifts.

To be fair to the draft concept, it does not propose to simply pave the floodplain. It proposes to decanalise a section of the Elsieskraal, retain the floodplain wetland, and manage stormwater with Sustainable Urban Drainage systems and detention ponds (Information Document pp.15 to 16, 23 and 25). That is the right direction. The problem is that this mitigation is concept-stage and unquantified, and the Flood Risk Assessment and the stormwater engineering study have not been released. Until they are, nobody can show that the proposed drainage offsets the effect of hardening the catchment. The public is being asked to support the permanent disposal before that evidence exists.

The part that should stop everyone

This is not a hypothetical tension. Both things are happening at once, in the same valley, funded and authorised by the same City. The C40 programme is rebuilding floodplain capacity because the science says that cuts flood risk. The disposal proposal would reduce floodplain capacity in the same system.

Neither the disposal documents nor the public engagement materials acknowledge this. The question has not been answered because it has not been asked in the right forum. That is what the formal objection and the EIA process are for.

This is not an argument against housing

Cape Town has a serious housing shortage. Well-located public land close to jobs, transport and services is where affordable housing should go, and the golf course sits on well-located public land. That case is real.

This article does not argue against housing. It argues for doing the flood studies before the permanent decision, not after. And it argues against paving one of the City's last functioning floodplain sponges in a catchment where the City is simultaneously spending money to rebuild that same sponge capacity next door.

The Flood Risk Assessment, the stormwater engineering study, and the full Environmental Impact Assessment have not been released. The public has been asked to comment on the permanent disposal of this land before seeing any of those documents.

The question that deserves a public answer, on the record, before any disposal is finalised: