USC FloodStudyUpdate Report - Flipbook - Page 262
assessments undertaken using this model.
Additional scenarios
should be added to reflect proposed development
cases.
The runs take approximately 0.5 to 1 times the simulated storm duration using a PC equipped with an
NVIDIA 1080 Ti GPU card.
Model users should run the base case and ensure that the results obtained are exactly the same as those
provided with the model before proceeding to edit the models.
5. IMPACT ASSESSMENTS USING REGIONAL MODEL FRAMEWORK
These hydrologic and hydraulic Regional Models have been developed to facilitate assessment of impacts
of proposed developments. While each proposed development will be different and the modelling may need
to be tailored for each assessment, the following provides a general outline of the process and parameters
that should be adopted.
5.1. Process
The general process that should be adopted involves the following:
1. If required, prepare a new sc
conditions at the time of the
assessment. The models may require updating to represent any development that has
occurred between November 2018 and the date of the assessment (for example, development
of a precinct upstream of the subject site). There may also be more detailed information at the
site of interest from detailed survey that may have been conducted, and this can be included
in the model. Any and all changes to the base case must be fully documented and justified in
the impact assessment report, and the impacts of the base case revisions on peak flood
behaviour must be reported.
2. Prepare a new scenario
conditions (post-development). The
proposed development will need to be included in the models. In the XP-RAFTS model, this
will typically involve refining the subcatchment boundaries to align with the topography and
hydraulic controls in the proposed development, and increasing the fraction impervious. In the
TUFLOW model, this will typically involve altering the terrain to reflect the proposed
earthworks, altering the surface roughness to reflect the proposed land use and incorporating
proposed hydraulic structures such as stormwater networks, detention basins and culverts.
3. Ensure consistency
conditions models. The models should be consistent between the two
scenarios such that the only difference is that of the proposed development. This will enable
an accurate assessment of impacts. For example, if catchments were subdivided further for
the proposed conditions, then these subdivisions should also be represented in the existing
conditions model. Modelling of the stormwater network, hydraulic structures and buildings
should use a consistent approach with that used for similar structures in the base case model.
4. Undertake an impact assessment. This involves a comparison of post-development peak
flows and pre-development peak flows at the boundary of the site, and a comparison of postWMAwater Pty Ltd
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