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

GROUNDWATER FLOW MODELLING
6.3.1 Regional conceptual model of groundwater flow through the flood plain
The Tame meanders across an urbanised flood plain comprising clays, sands, gravels and
artificial made ground to a depth of 5 m. Underlying the floodplain and rising to form the
valley sides, the sandstone aquifer has an effective base at >100 m, as defined by its contact
with the top of the less permeable Carboniferous Coal Measures.
The sandstone aquifer is a high porosity, low to moderate permeability formation. Flow is
generally considered to be single porosity though the effect of fractures is locally important.
Hydraulic anisotropy is present in the sandstone, with lower vertical conductivity resulting
from the presence of low permeability mudstone layers within the formation. The alluvial
sands and gravels are thought to be high-storage/high-permeability units and may have higher
conductivity along buried channels in a down valley direction. The made ground exhibits a
large range of storage and permeability values. The presence of clay horizons may lead to
localised semi-confined conditions. The riverbed material comprises sand and gravel and is
thought to provide little resistance to flow.
The regional groundwater flows to the river from the north (left) and south (right) sides of the
valley and the river flow increases across the area due to groundwater discharge. Groundwater
flow occurs through the sandstone in areas with a deep water table (>15m) such as the valley
sides. In areas with a shallow water table (