Jeanine Vonkeman

Stellenbosch University | SUN · Department of Civil Engineering

High sedimentation rates at Thwake Dam poses a threat to the dam's design life span. The SHETRAN hydrological model was utilised to estimate the long-term sediment loads. Three sets of scenarios were considered; observed rainfall + the European Space Agency (ESA) land-use changes for (a) the year 2000, for (b) the year 2016 and for (c) the predicte...

The Nqweba Dam is one of the oldest dams in South Africa and was commissioned in 1925 for irrigation. The original reservoir depth at the dam wall was 31 m, but over the years sedimentation has reduced the water depth to 9.8 m. The original storage capacity of 79 million m ³ has decreased to 46 million m ³ by 2020. The dam supplies the town of Graa...

Sediment accumulation in reservoirs leads to a loss in water storage capacity, potential contamination or dam safety issues, and low assurance of water or power supply. Typical sediment management strategies such as watershed erosion control, sediment traps (check dams) or sediment bypass systems reduce incoming sediment loads but do not directly a...

This paper evaluates the possible future impacts of climate change on sediment yield by incorporating predicted future climate data and a physically-based hydrological and sediment yield model, SHETRAN. The Nqweba Dam catchment (3681 km2) on the Sundays River, located in the semi-arid region of the Eastern Cape of South Africa, was identified for t...

This presentation evaluates the possible future impacts of climate change on sediment yield by incorporating predicted future climate data and a physically-based hydrological and sediment yield model, SHETRAN. The Nqweba Dam catchment (3681 km2) on the Sundays River, located in the semi-arid region of the Eastern Cape of South Africa, was identifie...

Boksburg Lake in the City of Johannesburg, South Africa, used to be a very popular and important public amenity and has now decayed into an unsightly, unsafe and contaminated water body. Of greatest concern to the local residents is the poor personal safety, the unpleasant odour of the lake water and aesthetically unattractive litter that lines the...

Boksburg Lake in the City of Johannesburg, South Africa, used to be a very popular and important public amenity and has now decayed into an unsightly, unsafe and contaminated water body. Of greatest concern to the local residents is the poor personal safety, the unpleasant odour of the lake water and aesthetically unattractive litter that lines the...

Bridge pier scour was simulated by a coupled fully 3D hydro-morphodynamic model and validated against 24 experimental datasets for a combination of different pier shapes, approach velocities and sediment bed material. The proposed numerical model adopts an Eulerian multi-fluid model to account for rolling and saltating particles and computes bed sh...

The existing Sir Lowry's Pass River downstream of the N2 Bridge is relatively small with a very wide floodplain that is inundated during major floods and makes new development unfeasible. It is proposed that the main river channel is rehabilitated to accommodate a flatter 1:230 slope, a 84 m width and 4 drop structures that consist of 38.5 m long o...

The Holsloot Diversion Works is required to replace a number of temporary rockfill diversion weirs as part of a more sustainable river management plan. It is located on the Holsloot River, 9.7 km southeast of Rawsonville and 11 km downstream of Stettynskloof Dam. The paper covers the weir's hydraulic design and hydraulic model testing, as well as g...

Pier scour has been cited as the main mechanism responsible for the failure of bridges spanning rivers. Despite extensive research since the 1950s, there is no universally agreed upon procedure to accurately predict the equilibrium scour depth. Experimental data was generated by 48 tests with four flows and three pier shapes to evaluate the capabil...

The determination of extreme flood levels in an estuary should consider river floods and waves penetrating the estuary. The Breede River estuary in South Africa, 50 km in length, is discussed as case study in this paper. A two-dimensional hydrodynamic model Mike21C of the DHI Group of the 50km estuary (including the estuary mouth) was set up and ca...

The Orange River Re-Planning Study (ORRS, 1997) recommended that the proposed Noordoewer/Vioolsdrift Dam (NVD) site be further investigated as possible dam development downstream of Vanderkloof Dam, in the lower reach of the 2200 km long Orange-Senqu River. The Lower Orange River Management Study (LORMS, 2005) recommended that a re-regulating dam b...

This paper discusses the possible impacts on the Orange River Estuary, of the proposed Noordoewer / Vioolsdrift Dam (NVD) project on the lower Orange River located 300 km upstream of the estuary. The flow patterns and sediment dynamics at the estuary were evaluated as supporting information to the feasibility study of the proposed NVD site. A stati...

This paper investigates the hydraulics of raising the existing diversion weir and canal on the Holsloot River. The key findings of this study are that the raised Holsloot diversion weir (0.3 m) has a significant benefit to increase the diverted flows when the Holsloot River flows are between 30 and 120 m 3 /s. The raised weir will have limited impa...

This paper discusses the optimization by physical modelling of the hydraulic design of the stilling basin for the proposed Xhora Dam in the Eastern Cape (currently under construction). The key hydraulic components of the dam are: a side channel spillway 25 m in length, a discharge carrier consisting of a trapezoidal concrete lined chute (5 m wide a...

The key aim of the study was to determine whether a hydro-morphodynamic model, recently developed by Sawadogo (2015), could be applied to simulate local scour around a cylindrical bridge pier. ANSYS Fluent solved flow equations for the Eulerian multiphase and k-e turbulent models which were coupled with sediment transport and bed deformation sub-mo...