1 minute read
Figure 3: Exile Bay Ground Level Survey
Figure 3: Exile Bay Ground Level Survey
3.3.3 Drainage Network Data
Advertisement
Drainage network data is a critical hydraulic model input. Stormwater elements, inclusive of conduit size and invert levels, are input into the TUFLOW hydraulic model. During the model simulation, these structures are used to convey flow, with excess flow moving overland. Most drainage assets in the study area are owned and maintained by Council.
Council has supplied GRC Hydro with a GIS layer of the drainage network inclusive of structure dimensions and depth to invert (where available). Where the depth to invert was not available, invert levels were interpolated from known upstream and downstream inverts or, where interpolation was not possible, estimated based on an offset from the LiDAR (0.4 m specified by Council). Where dimensions are unavailable and the upstream and downstream structure sizes are known, structure sizes were interpolated.
The drainage network is shown in Figure 16 (page 51).
3.4 Hydrologic Data 3.4.1 Recorded Rainfall Data
Recorded data was collected to define historical flood events in the study area and for use in calibration and validation of the hydrologic/hydraulic models. In general, the complete rainfall record of rainfall gauges in the vicinity of the study area was collected, and from this individual rainfall events were extracted. It is noteworthy that this data collection has included comprehensive Sydney Water gauge data.
Gauges included both pluviometers and daily read rainfall. Pluviometer gauges continuously record rainfall in small time increments (generally 5 minute intervals or less). This data forms rainfall hyetographs which show the pattern of a rainfall event over time. Daily read rainfall gauges provide a total recorded rainfall depth over a 24 hour period. Typically, daily read gauges are more common. They inform the spatial variation of a rainfall event albeit without temporal distribution so are of limited use in this study.
Data was available from the Bureau of Meteorology and Sydney Water. Table 2 lists the gauges for which data was obtained, and Figure 4 shows their locations.
