The Village of Gunning has a population of about 550 and is located on the Hume Highway midway between Yass and Goulburn in the headwaters of the Lachlan Valley. Meadow Creek (also known as Gunning Creek) flows through the town and joins the Lachlan River 4 km downstream of the village. Gunning is subject to main stream flooding from Meadow Creek which has a catchment area of about 106 square kilometres at the Hume Highway bridge to the south of the Village. Flows from a minor tributary cross the highway to the west of the bridge, before flowing around the western side of Gunning and joining Meadow Creek. Problems also originate from overland flows from the local sub-catchments situated within the developed parts of the village.
The objective of the flood studies was to define flood behaviour in the villages in terms of flows, peak levels and extents for floods ranging between 20 and 200 years average recurrence interval, as well as for the Extreme Flood.
The flood study had three components:
- Preparation of the Data Collection Report – L&A, 2012. This component involved the collection and review of available data on historic flood behaviour, as well as available survey information and provided recommendations for the collection of additional data for preparation of the catchment and floodplain models.
- A hydrologic component which included preparation of the RORB hydrologic model of the study catchment, testing the sensitivity of model parameters for historic and design storms and adoption of model parameters for design flood estimation; derivation of design storm rainfalls and their application to the model to define design discharge hydrographs.
- A hydraulic component which comprised the preparation and testing of the TUFLOW hydraulic model of the main streams and floodplains and the application of historic and design discharge hydrographs to the model to define indicative extents and depths of inundation, water surface profiles, flows and velocities for the design floods.