Camphersdrift River and Stormwater Rehabilitation

In December 2021, the City of George experienced severe weather that caused varying degrees of stormwater damage to infrastructure and river embankment erosion throughout the municipal boundary. A significant portion of this damage affected the Camphersdrift River, which flows through the centre of town. The municipality successfully applied for disaster relief funds, enabling the implementation of several civil engineering projects aimed at mitigating damage, repairing infrastructure, and reconstructing the affected areas.

Nine sites were identified along the Camphersdrift River, spanning the Camphersdrift and Van Riebeeck Garden areas and extending downstream toward the centre of town near the CJ Langenhoven Bridge. The primary objective was to repair the existing stormwater infrastructure and restore the damaged river embankments using environmentally friendly protection methods.

The project generated employment opportunities due to the labour-intensive nature of the construction activities. Additionally, it enhanced the quality of life for local residents who use the riverbanks and adjacent areas for recreational purposes on a daily basis.

The project brought together a diverse range of engineering and landscaping services to create a functional, safe, compliant, and aesthetically pleasing river embankment. The civil and structural engineering services were provided by Lukhozi Consulting Engineers, ensuring sound design and construction.

The river channel’s shape is most affected by flows that occur frequently enough to mobilize materials on the streambanks and streambed—typically smaller bankfull flows. To evaluate the erodibility of the banks and beds, shear stress calculations were performed. Based on the hydraulic analysis, a combination of bank protection techniques was applied, including Void-Filled Riprap (VFR), Reno mattresses, gabion baskets, and traditional riprap methods.

The Void-Filled Riprap (VFR) method was predominantly used to protect the majority of the embankments where erosion occurred. This method was recommended because it replicates natural riffle rock formations commonly found in streams with coarse gravel and cobble beds. The approach involves arranging standard riprap stones to create voids, which are then filled with a carefully graded mix of cobbles, gravel, sand, and soil. The resulting structure is tightly interlocked and allows surface water to flow through.

One major advantage of VFR is that it promotes the connection between groundwater and surface water, creating an important ecological zone within the streambed known as the hyporheic zone. This zone supports various organisms through critical stages of their life cycles and provides a substrate for riparian vegetation growth (see Figure 1).

The embankments were graded with gentler slopes, and the size of rocks and apron lengths were carefully designed to withstand shear stresses and dissipate energy. Unlike rigid structures, rock riffles adapt to ground settlement and are less likely to experience localized erosion along their edges, which could otherwise expose substructures and cause cracking.

The successful rehabilitation of the river’s streambanks and streambeds within the allocated budget was a major achievement. This project not only created jobs during construction but also enhanced opportunities for the George community to better utilize the riverbanks for recreational activities in future.

Project Team

Environmental Assessment Practitioner – Sharples Environmental Services

Aquatic Ecologist and Water Use Consultant – Upstream Consulting

Indigenous Vegetation Rehabilitation -Confluent Environmental

Geotechnical Engineer – Outeniqua Geotechnical Services

Civil Engineering Surveyor -Eden Geomatics

Structural Engineers – Lukhozi Consulting Engineers – Mr Pieter Smit

Civil Engineers – Lukhozi Consulting engineers – Mr Koenraad Potgieter

Hydraulic Engineers -Lukhozi Consulting Engineers – Mr Patrick Dallas