Should there be a causal link, Kim, you may well find that “a broken watermain every 3 to 4 months” (welcome to Cape Town, by the way) leads you to ageing infrastructure and the good intentions of our foresters of yore.

Because pine, gums and other aliens burn at up to ten times the intensity of fynbos, the damage they cause is not only apparent in razed, gutted or damaged built structures, but hidden. Their stumps and taproot systems continue burning for weeks after a fire has apparently been extinguished, leading to land subsidence, mudslides, rock falls and sink holes.

SANParks was forced to close Silvermine west for far longer than Silvermine east, solely because of the damage and dangers caused and presented by burnt commercial pine and destabilisation. In March 2015, SANParks communicated envisaged closures of “six to twenty four months”.

Pinus radiata (the Monetery pine) will, according to Wikipedia, sink its tap root “downward as far as physically permitted by subterranean conditions. Roots have been discovered up to 12 meters long. Efforts to remove large quantities of the non-native tree in areas of South Africa have resulted in significant increases in accessible water.”

Similarly, Pinus pinaster relies as much on a deep tap root and well-developed secondary root system. I’m afraid your burst mains are an urban variant of this increased water accessibility and must be taken up with the City – which, working closely with SANParks since the 2015 Muizenberg Fire, has invested much in restoring the urban edge and services disrupted by the plantation fire.

The felling of compartments on the slopes (50-400 metres) has not occasioned an outcry. However, if a link can be shown or made between water cuts and the large-scale clearing of burnt pines, it will demonstrate the hidden (as opposed to the immediately apparent) potential for devastation by these alien trees. And any link made between water disruption and the felling of healthy pines on the lower slopes (<50m) going back to 2011 might well force MTO Forestry to take greater care in conducting commercial operations so close to an urban area.

Tokai's water table is seasonally high, but is drained by several rivers, notably the Prinskasteel, Keysers and Spaanschemat Rivers, which flow to the Zandvlei Estuary. SANParks addressed the need for services infrastructure upgrades within TMNP's Lower Tokai section in a paper published in 2010, before tree felling began in the area.

Note: Alien Acacia bushes sink their roots 150-400% deeper than our cheerfully resilient Proteaceae.