eTheses Repository - University of Birmingham

6.1.2 NOURB CASE
The NOURB land cover map was created in which all the urban areas were removed and
replaced by a combination of rural land cover types, in order to represent the land cover
prior to any urbanisation. The distribution of the rural land cover at the sub grid scale was
created using combinations of the two rural land cover types (‘Meadows’ and ‘Mixed
forest’), so that the land cover map represented a realistic rural state, rather than replacing
all of the current urban land use with either of these two rural types. This assumes that in
the past the city of London was surrounded by fields and woodlands, as documented in
Hunt (2005).
6.1.3 COMBINED series
Land cover maps were created from the current base case urban land cover (URB_BASE)
in which the urban surface was removed for all points for which the radial distance from
the centre of the domain was more than a critical radius. The current extent of London can
be roughly represented as an area characterised by a radius of about 45-50 km. It was
necessary to balance the availability of computing resources with the necessity of
performing enough simulations to represent the realistic growth of the city from a pre-
urban state to the current extent. For this reason eight model simulations were performed
with the critical radius of the urban area increasing from 5 km to 40 km in steps of 5 km
(COMBINED series – see Table 6.1).
In order to simulate a realistic density distribution within the model domain, the urban land
cover fraction P(i,j) within each grid cell was also reduced and multiplied by a factor
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