18 May 2022

Waterfall’s H₂O Strategy

Stormwater and water management at Waterfall

This is the second article in our series examining the aspects that make Waterfall a world-class environment. Here, our spotlight turns to stormwater and water management. As a growing metropolis, these components are critical to the development’s infrastructure and sustainability.

Waterfall centres on creating a green environment that is good not only for residents and the businesses operating here, but for the planet as well. Everything is built according to sustainable principles and practices. Every development, whether it is commercial, logistics, retail or residential, must be efficient, cost-effective, and eco-friendly.

You might know how our landscaping focuses on indigenous, water-wise plants, but this is just one element of a complex ecosystem of support that exists around stormwater and water management.

Thys Redelinghuys, General Manager of the Waterfall Common Services Company, along with a few other experts of the wider teams and entities working across the development, explain several elements guiding Waterfall’s approach in this regard.

Stormwater

“When you have undeveloped land, the flow of rainwater is moderated by soil and vegetation. The water seeps into the ground and the vegetation stops it from flooding or causing erosion. Once you start developing and creating hard surfaces, the result is a concentrated, fast runoff of rainwater that can cause significant problems. With the Jukskei River running through Waterfall, we have seen how just 20mm of rain upstream from us can come down like a flood,” Redelinghuys says.

A significant challenge, therefore, has been that of erosion control. One of the ways in which Waterfall has managed this is through the building of attenuation dams that have become part of its green belt. These carefully designed civil structures blend into the natural landscape of the nature areas and play a critical role in controlling the flow of rainwater throughout the entire development.

“All of this comes down to managing stormwater as effectively as possible, in order to minimise the possibility of flooding and soil erosion. Slowing down the water, managing it and controlling it, is vital in our efforts to mitigate the risk of soil erosion,” says Kenneth Gaynor, CEO of Waterfall Country and Village Estates.

The heavy rainfalls experienced in Gauteng this past season have certainly highlighted the importance of water management. According to the latest figures, for 2021/2022 Gauteng recorded a seasonal rainfall of 1176mm. During the previous season, 2020/2021, the figure was 774mm of rain, an increase of more than 50% year-on-year.

Dam innovation: a key focus

Waterfall has established a large attenuation dam within the Waterfall Country Village Estate, and eight other smaller attenuation dams across the development. “These dams significantly reduce the risk of flooding and form part of the development’s strategy to reduce soil erosion. However, the build-up of silt, especially in the main dam due to rainfall and soil disturbance, remains a key challenge. Silt management across all the dams is a vital part of our focus as we must ensure the dam is safe for the bird and aquatic life and that it can be used for recreational non-motorised sports by residents. To help manage silt in the main dam, the existing island was supplemented with the creation of two additional islands,” says Gaynor.

Safety engineers further pointed out that silt was starting to cause problems on the spillway wall. Because silt is not stable and cannot bind together, this could potentially cause the wall to collapse. The main dam was also getting shallow, having a negative impact on the ecology. “By using the silt to increase the size of the first island and form the two new islands, the dam was deepened to its original depth. This has been an ecologically-friendly way of treating the problem, even though silt must be continuously managed. We aim to desilt the dams eventually,” explains Gaynor.

In the main dam, the team has removed some of the reeds and focused on introducing indigenous plants. Furthermore, many distinct species of fish have been added to the dam to support the natural process of keeping it healthy and creating a thriving ecosystem. Residents can even fish on a ‘catch and release’ basis.

Waterfall has also reached out to some of the schools on the development for pupils to come and observe the wetlands, erosion, and all the interventions that have been implemented. This reinforces the objective of teaching children in the area how best to live in harmony with the environment.

Clean water

“Waterfall has a water use licence that allows us to irrigate common areas of the development from the river. Unfortunately, the river water is at times very dirty. Apart from the litter that comes from upstream, the water is soiled to the point where the E.coli bacteria count runs incredibly high at times. We pump water from the river into an ozone water treatment plant to bring down the E.coli count to an acceptable standard that we can use for irrigation purposes. On a busy day, the plant treats approximately two million litres of water,” says Redelinghuys.

“Furthermore, all water features situated within the residential estates not only use water taken from the Jukskei River, but this water then flows back into the river. Water is a precious resource that must be managed optimally and therefore no council water is used for our water features. Although there are no formal measures in place, we encourage residents to practise water-wise habits. We provide articles and tips on how to do this through various communication channels and frequent newsletters,” adds Gaynor.

This extends to advising residents to install JoJo tanks in compliance with the estate guidelines, using their gutters for harvesting rainwater, encouraging them to plant indigenous, water-wise vegetation, and so on.

Roads and drainage

The Waterfall Common Services Company is additionally responsible for the communal areas in Waterfall. This includes the roads. Even though the stormwater and road infrastructures are the responsibility of the council, the company uses a service provider at least once a year to inspect the stormwater drains in Waterfall to ensure they are clear.

“This helps prevent the roads from flooding during the rainy season. Stormwater pipes are sized based on engineering design standards that take into account rainfall statistics for an area. However, they are not designed to deal with extreme conditions such as a cloud burst, for example. There will therefore be occasions where the roads may flood even if the stormwater pipes are clear. It is all about balancing – dealing with stormwater effectively while not making it cost-prohibitive from a development perspective,” comments Redelinghuys.

On the commercial side of the development, Attacq aligns with the parameters of the council requirements when it comes to stormwater management, says Lourens du Toit, Infrastructure Manager at Attacq. “As the commercial developers of Waterfall, Attacq conducts ongoing maintenance to ensure longevity of the road surfaces and drainage systems around the commercial areas of the city. The council requires compliance with applicable and relevant engineering standards. All our designs are therefore submitted to the council for approval, and we collaborate with the council’s maintenance depots to maintain and ensure an effective stormwater system,” he explains.

An example of such collaborative action was seen at Waterfall Corner, where a stormwater pipe was found to be leaking below the surface. Before extensive damage to the road manifested, the developers stepped in and fixed it on behalf of the council.

As Waterfall grows, pockets of land become active construction sites in built-up urban areas. “There is a huge emphasis on stormwater management during construction. For instance, we cover all kerb inlets with shade net cloth to prevent silt entering the system and causing blockages. We also prevent silt runoff on the road surfaces, as this can be hazardous to motorists. In some instances, we place hay bales to ensure there are no issues, as we are committed to managing this growing city with the utmost care. And because Waterfall has numerous operational teams on the ground, there is also very little litter lying around that can cause blockages in the stormwater pipes,” adds du Toit.

Over and above this, as part of the development’s wider sustainability efforts, many of the commercial buildings in Waterfall have rainwater harvesting systems in place. This includes Deloitte, with 270 kilolitres-worth of rainwater harvesting storage and the Mall of Africa, with 2 200 kilolitres of stored water.

“A development like Waterfall takes careful planning and consistent management across a variety of key infrastructure-related areas. Our stormwater and water management processes and systems are effective because they are planned well and maintained well – and this will remain a key focus for our world-class city,” concludes Redelinghuys.

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