The impact of urban groundwater upon surface water - eTheses ...

GROUNDWATER FLOW MODELLING
presence of rock-filled support gabions. Modelling therefore provides a useful approach to
understanding seepage zone processes.
6.6.2 Application of the FAT3D channel scale model
The FAT3D model was used to simulate the seepage face by incorporating seepage cells in
the banks above the river cells. These cells can only discharge groundwater when the
groundwater head is above the cell centre elevation. These cells were located in the riverbank
to a height of 0.5 m above river level to cover the maximum likely extent of the seepage face
according to field data. Under steady state conditions seepage discharge was found to occur
only through the lowest seepage cell adjacent to the river cell. The model simulated the
discharge occurring across the seepage boundary for varying geological conditions and
boundary heads under both transient and steady-state conditions. Under transient conditions
additional fixed head river cells were added to the banks to reflect the increase in river depth
and the coverage of the seepage cells was maintained at 0.5 m above river level.
6.6.3 Results and discussion
Steady-state modelling indicated that for an isotropic uniform geology no discharge occurred
across the seepage face when conductivity was > 2 md -1 . Discharge did occur when
anisotropy ( Kx 2 md -1 , Kz 0.2 md -1 ) was introduced, amounting to