USC FloodStudyUpdate Report - Flipbook - Page 257
Since the focus of the flood study was the entire catchment, an areal reduction factor was applied to all
subcatchments according to ARR 2019 (using the equations found in the Datahub output), adopting an
area of 56 km2 (the Upper South Creek catchment area to Bringelly Road) for all events except the PMP.
3.5. Running the Model
The model should be run using XP-RAFTS 2018.1.1. Each event and duration combination has been set
up in a different model file, meaning that each model can be run and results obtained for each design storm
separately.
4. TUFLOW METHODOLOGY
4.1. Overview
A 1D-2D linked TUFLOW model has been developed for the Upper South Creek Catchment. The model
utilises the TUFLOW Highly Parallelised Computing (HPC) engine to simulate flooding across the 2D
domain, with 1D hydraulic structures (culverts, pits and pipes) dynamically linked to the 2D domain. The
model represents catchment conditions as at November 2018 (when the LiDAR was obtained). Features
within the model are generally separated into existing urban features and existing rural features. The
guidance provided in Reference 4 has been used to develop this model. The model was calibrated to the
June 2016 flood event, at the Elizabeth Drive gauge and to a number of flood marks across the catchment.
Impact assessments undertaken using the model should follow the same general principles for
schematisation as outlined below.
4.2. Extent and Resolution
The TUFLOW model 2D domain covers the entire Upper South Creek Catchment, from its headwaters in
Oran Park and Gregory Hills to approximately 250 m downstream of Bringelly Road. The model also
includes the tributaries of Kemps Creek, Scalabrini Creek and Bonds Creek. The Bonds Creek catchment,
which traverses Denham Court (outside the study area), is only modelled from Camden Valley Way to
Bringelly Road. The 2D domain covers an area of approximately 78 km2. While the model has been
developed to be run at numerous grid sizes, the design flood events have been run with a grid size of 3 m,
which provides a balance between resolution and run time.
A one-dimensional (1D) representation of South Creek downstream of Bringelly Road was retained from
the Upper South Creek Floodplain Risk Management Study and Plan (Reference 5) for the purpose of
calibrating to the stream gauge located at Elizabeth Drive. This portion of the model, however, has been
removed for the design flood events as it is beyond the required study area.
4.3. Terrain
The TUFLOW model 2D terrain is based on the November 2018 LiDAR dataset. The 1 m DEM was read
into the TUFLOW model directly to develop the underlying terrain.
WMAwater Pty Ltd
118112: 201030_USC_Regional_Model_User_Guide_Final: 30 October 2020
7
