The Rosebank Canal Rehabilitation Project on the Liesbeek, launched at the beginning of the year is well on its way to achieving its goal – turning a canal into a river and bringing nature back into the city.
Launched in January by Future Water (an inter-disciplinary research institute at the University of Cape Town (UCT), the Water Hub (a research, demonstration and training centre) and the Friends of the Liesbeek (FoL) and funded by the Dutch Ministry of Foreign Affairs, the pilot project focuses on a 200 m stretch of the canal running through Rosebank (“Canal gets a clean-up”, People’s Post, 22 February). On Saturday 26 February and on Saturday 12 March – the first two of three volunteer days – the Rosebank canal project team, together with the Friends of the Liesbeek team and community members first weeded and then re-designed the canal, reinforcing four rock weirs and flattening sediment.
On Saturday 26 March, about 1 400 Palmiet seedlings were transferred to this section of the canal.
Michael Lambrecht, the Rosebank Canal Rehabilitation Project manager, says Palmiet is a very good pioneer species. Lambrecht recently completed his masters in Environmental and Geographical Science at the UCT. “It anchors the sediment. Then we will bring in some more indigenous plants.”
He says they hope the seedlings will create more habitat for nature to come back into the river.
“Already we have found more fish species such as the Cape Galaxias, which are probably more due to the weirs being built and enforced because the fish need slower-moving water. With the weirs built, the water level has risen which creates a good habitat for them.”
Lambrecht says the idea is for the weirs to force the water across the breadth of the canal. “So as the water level has risen, it has expanded outwards and it is wetting the soil. Because the plants we are planting need wet feet – it is a semi-aquatic plant – we need the soil to be wet so it can grow.”
Rosebank and Mowbray residents were initially introduced to the project during an information session held at the Liesbeek near the play park in Rosebank on Friday 11 February.
More than 70 residents attended the session.
Lambrecht says that was a strong indication that people really care about this space.
“And just coming here in the morning and afternoons; there are so many people walking their dogs here. People are really passionate about this space and I can see how much this space means to them. We have constantly been communicating with the community. I think they feel involved.”
He says some residents have expressed their concern about possible flooding in the future.
“Because it is a concrete canal, when the rainfall comes, the water level quickly rises. It hasn’t flooded I think in 10 or 20 years but because residents have moved closer and closer to the river, the concern is that if it should flood it would damage their properties.”
However, he says part of the project was removing a lot of weeds, flattening the sediment and taking out three, four-meter high trees that grew inside the canal.
“A tree will have a big impact on the flooding. We think that by taking out the weeds and trees, and planting the Palmiet it will have a stabilising effect.”
Lambrecht explains that as a semi-aquatic plant, Palmiet is adapted to growing on banks. He says a bank of a river is going to flood from time to time and there is a lot of erosion that happens on banks. As a result, Palmiet has developed an aggressive adventitious root system. It spreads out and anchors the plant really well. Also, it can flatten down when it floods.
“The plant will flop down and then as soon as it is finished flooding, it pops back up. We are hoping the hydraulic resistance is not going to be too much that it would create flooding.
“Obviously, it is a pilot study. We are just testing it on this small stretch, so we don’t know 100% but we are fairly confident it is not going to have a negative effect.”
The pilot project also forms part of a research project, which is also headed by Lambrecht.
Three Dutch students of Hogeschool Rotterdam arrived in Cape Town in mid-February. Together with two students from UCT, they have already started their respective research studies on the effects the rehabilitation efforts are having on the canal.
“Because it is a pilot project, we are trying to work out what changes and then you can make recommendations for the future. The idea is if Palmiet really works well in this section, we can say to the City of Cape Town that Palmiet, which is a very low-maintenance species, is very effective at improving the water quality and that it brings back frogs, fish and macroinvertebrates (small aquatic animals and the aquatic larval stages of insects) – things like that,” Lambrecht says.
