Specialized Shoreline Model for Mine Planning
Without the ability to reclaim land in areas rich in diamonds, the Namdeb Oranjemund mine (Namibia) would close down. Provision of a specialist modelling service by WSP allows for the planning of this strategic land reclamation essential to extending the life of the mine, where on-land diamond reserves have been almost totally depleted. The shoreline model predicts shoreline accretion in response to a range of possible mine sediment discharges, such as from dredgers and screening plants. The key challenge was to ensure the model accommodates non-linear increases in alongshore sand transport in response to major beach build-up, and in a very dynamic wave environment. This problem was solved by developing specialized model formulations and, through comparison with detailed shoreline and bathymetry measurements, ensuring that these formulations represent reality.
This modelling tool may continue to benefit Namdeb (of which the Namibian government is a major stakeholder) and its employees by facilitating strategic land reclamation for diamond mining.
Land Reclamation Opens Up Possibilities
As on-land diamonds are depleted, Namdeb Diamond Corporation is reliant on mining diamonds just offshore of the shoreline. This mining is possible by reclaiming land through the discharge of large volumes of sand and gravel onto the shoreline.
The client required specialist coastal expertise to investigate shoreline accretion, resulting from targeted shoreline discharges of sand and gravel, which emanate from the mining process. Predictions of shoreline accretion allow for the planning of mining diamondiferous bedrock gravels in the accreted/reclaimed areas.
Using Technology to Model the Shoreline
The UNIBEST CL+ numerical shoreline model was adapted, in collaboration with the suppliers, Deltares, to accommodate the unique conditions of rapid shoreline accretion due to shoreline sediment discharges in a dynamic wave environment with steep nearshore slopes. The model was calibrated to represent the evolution of the shoreline, incorporating accretion of some 400 m in places, over a period of 18 years. The model was also adapted to successfully represent volumes of sand and gravel accretion in the nearshore region.
This specialized modelling tool is employed to predict shoreline evolution, in response to various scenarios of sand and gravel discharges, up to 40 years hence.
Our team delivered the following:
Analysis of beach and nearshore morphology, employing a specially adapted visual basic routine
Computational modelling of coastal processes: wave transformation from offshore to nearshore
Generation of wave-driven currents at the shoreline
Consequent transport of sand and gravel alongshore
Interpretation of predicted shoreline evolution.
Employing the calibrated shoreline model, the client can assess the accretion which results from a range of sand and gravel discharge scenarios. With a year-by- year prediction of shoreline accretion, the client will then be able to plan for the mining of the accreted area to recover the diamondiferous gravel near the bedrock.