Diagram 5: Provisional Hydraulic Hazard Categories

4-6 August 1986:

• digital records from the Elva Street gauge show no record for this event. However, Reference 1 indicates a peak of 1.95 m obtained from data collected as part of Reference 8. • the St Sabina pluviometer malfunctioned, and the Elva Street pluviometer recorded a maximum of 21 mm in 30 minutes which is only modest rainfall. For this reason, this event could not be used for calibration.

Summary

Five events (3rd, 7th, 10th and 17th February 1990 and 18th March 1990) were available for calibration of the Elva Street gauge and two events (10th February 1990 and 2nd January 1996) for calibration of the TUFLOW model in the 2016 Powells Creek Revised Flood Study (Reference 2). These same events were used in the current calibration process.

3.6. Design Flood Modelling

Following model establishment and calibration the following steps were undertaken: • design tributary inflows were obtained from the DRAINS hydrologic model and included in the TUFLOW model. • assessment of the design event causing the maximum water levels which is termed the critical storm duration. • sensitivity analyses to assess the effect of changing model parameters and the assumed water level in the Parramatta River. • assessment of possible effects of climate change on design flood levels.