THE INFLUENCE OF GEOMECHANIC and HYDROLOGIC UNCERTAINTIES ON SCOUR AT LARGE DAMS: CASE STUDY OF KARIBA DAM (ZAMBIA-ZIMBABWE

A new engineering model, the Comprehensive Scour Model (CSM), has been developed for prediction of erosion in fractured media, such as rock, concrete or clays (Bollaert, 2004; Bollaert and Schleiss, 2005). The model is physically-based and relies on break-up by progressive fracturing of existing discontinuities as well as on subsequent dynamic ejection of so formed loose elements. It is not only able to predict the ultimate state of scour, but also the time evolution of the phenomenon as a function of flood duration and discharge. In the following, the model is applied to scour formation of the plunge pool downstream of Kariba Dam (Zambia-Zimbabwe). Emphasis is given on the influence of rock mass resistance and flood duration uncertainties on scour evolution as a function of time.