17.1  Flood management

17.1.1  DC800 flooding and other investigations

The 2001 Australia Day weekend rainfall event caused flooding in the DC800 catchment. This occurred at a time when transmission flows of 300 ML per day were occurring in DC800 for DLWC to supplement the Yanco Creek. Rainfalls of around 75 mm, with some readings of up to 100 mm, were recorded on farms in the DC800 catchment over that weekend. The results of these combined flows were that the drains quickly filled, water back-flooded up farm drainage inlets, growing crops were flood-affected and drain-off times from farms were extended significantly.

As reported in the past two AERs the full length of DC800 from Bridge Road to the Yanco Creek has been cleaned out to reduce flooding. If this work had not been carried out the 2001 Australia Day weekend flooding event would have been significantly more serious.

Measures being taken to reduce the effects of flooding in DC800 include:

• Planned capital expenditure to automate regulators at the top of Bundure Main so that big flows can be cut out quickly following rainfall cutbacks.
• Planned installation of Supervisory Control and Data Acquisition (SCADA) on more escapes.
• Negotiations with DLWC to limit the size of diversions down DC800.
• Request to DLWC to fast-track automation of Tombullen Inlet so that water can be quickly cut out of the Main Canal.
• Flap valves to be installed on the downstream end of drainage inlets where back flooding occurred.
• Investigations are continuing into reducing restrictions in flow along DC800, particularly restrictions caused by piers of bridges.
• Investigations are continuing into alternative ways of conveying water to the Yanco Creek, given that suitable cost recovery can be agreed.

17.1.2  Flood control works

The siphon under the Main Canal downstream of Tubbo Wells Escape was cleaned out with specialized high pressure jetting and suction equipment.  The flood control levee banks were inspected.