Sealed Judgement

3.3            Pre-Development Model

3.3.1          Catchment Properties

Sub-catchment delineation was undertaken based on the 2015 LiDAR DEM. For the pre-development
case, the drainage area was divided into three (3) sub-catchments (namely, A, A1 and EXT as shown
in Figure 3-1). It is noted that the west end of the Site (designated as Wetland Rehabilitation zone)
was not included in the catchment delineation as this portion of the Site will not be affected by the
development.
It was also assumed based on available contour data that the external catchment (EXT) drains down
Sanctuary Drive, bypassing the Site. Table 3-2 provides the main catchment properties (area and
impervious percentage).



Table 3-2     Pre-Development Catchment Properties

 Sub-catchment       Area(ha)         Impervious Value (%)

         A             0.326                     2.9

        A1              0.124                     0

        EXT            0.099                     80




Figure 3-1 Pre-Development Catchment Plan




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