A two-dimensional hydrodynamic model for the St Lucia Estuary mouth.
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Date
1993
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Abstract
The reduced fresh water input into the St Lucia Estuary combined with the increase
of sediment in the St Lucia Lake System has necessitated the implementation of a
dredging programme. To ensure the effectiveness of the dredging programme, the
behaviour of the sediment under various flow and tidal conditions needs to be
determined.
To establish how sediment will move, it is necessary to understand the hydrodynamics
of the estuary. To achieve this, a hydrodynamic model which can be linked to a
sediment transport model needs to be developed. Various existing types of
hydrodynamic and sediment transport models are reviewed, to determine their
suitability for the above purpose. Results of the analysis indicate that a two-dimensional
hydrodynamic model is required.
The two-dimensional hydrodynamic model developed is based on the momentum and
continuity equations for an unsteady, non-uniform, free-surface flow for an
incompressible fluid. The two dimensions are in the horizontal plane and flow is
averaged over the depth. The equations are non-linear and are not decoupled, thus
a numerical technique was needed to solve them. An Alternating Direction Implicit
technique has been used. Boundary conditions in the modelled region were specified
as flow velocity at the upstream boundary, and water levels, relative to the Mean
Lake Level, at the downstream boundary.
Two short simulations using hypothetical data were run on a 80826 IBM compatible.
Results of the simulation indicate two areas where irregularities in the model output
are a consequence of the use of hypothetical data in defining the boundary conditions.
Recommendations for the collection of data in order to improve and calibrate the
model are discussed.
Description
Thesis (M.Sc.)-University of Natal, 1993.
Keywords
Sedimentation and deposition--KwaZulu-Natal., Estuarine sediments--KwaZulu-Natal., Hydrodynamics--Mathematical models., Theses--Geology., Saint Lucia Estuary (KwaZulu-Natal)