Gawler River Flooding

The Hon. J.M.A. LENSINK (14:39): I seek leave to make a brief explanation before asking the Minister for Water and the River Murray questions regarding flooding in Virginia.

Leave granted.

The Hon. J.M.A. LENSINK: In the Stormwater Management Authority's priorities for stormwater management planning in South Australia 2016-20 it states under 'High Priorities':

Although the GRFMA (Gawler River Floodplain Management Authority) is currently investigating further flood mitigation works on the Gawler River System which may include levee works in the vicinity of Virginia as a growth area in the 30-year plan for metropolitan Adelaide it is now appropriate that a separate SMP be developed for the Virginia township to cover flood threats from the Gawler River, flooding from other catchments and flooding from internal drainage in the town.

My questions for the minister are:

1. What advice has the minister received from the SMA in relation to flood mitigation in this region?

2. Does the current Stormwater Management Plan comply with the SMA guidelines, as required under recent amendments to the Local Government Act?

3. Has the minister received any advice that new coercive powers under the act will be required to prevent future flooding?

The Hon. I.K. HUNTER (Minister for Sustainability, Environment and Conservation, Minister for Water and the River Murray, Minister for Climate Change) (14:40): I thank the honourable member for her most important, and might I say, very sensible questions, compared to the previous one. I am advised that major flood flows occur in the Gawler—

The Hon. D.W. Ridgway: She would be a good leader.

The Hon. I.K. HUNTER: I don't want to tarnish any promise that she might have in terms of the leadership stakes, Mr President. Any endorsement from me might not do her well. But I would just say that she comes into this place well prepared, well researched and asks sensible questions, unlike her leader.

The Hon. G.E. Gago: And she doesn't make things up.

The Hon. I.K. HUNTER: And she certainly doesn't make things up, that's correct. I am advised that major flood flows occur in the Gawler River every 10 to 15 years on average. Prior to the recent flood in September 2016, the previous major flow occurred in November 2005, is my advice. This 2005 event resulted in significant flooding in and around the Virginia township, which I am also advised was due to the failure of a riverbank levee.

I am also advised that a one in 100-year flood would be likely to have substantial impacts on the Gawler, Virginia and Two Wells townships, as well as horticultural and rural living land near Virginia and north of the river towards Two Wells.

The Gawler River Floodplain Management Authority was formed in 2002, I am advised, as the key mechanism to address flooding concerns in the region. The authority is a regional subsidiary under the Local Government Act 1999, with six constituent councils: the Adelaide Hills Council, the Barossa Council, the Town of Gawler, the Light Regional Council, the District Council of Mallala and the City of Playford. The authority's main purpose is to deliver and maintain flood mitigation infrastructure on the North and South Para Rivers. Both of these rivers join at Gawler to form the Gawler River. The authority has overseen major flood mitigation works over recent years.

Construction of the Bruce Eastick North Para Flood Control Dam was completed in 2007. Modification of the South Para Reservoir spillway to improve the flood mitigation effect of the South Para Reservoir was completed in 2012. Both the state government (through the previous Catchment Management Subsidy Scheme and then through the Stormwater Management Authority) and the commonwealth government (largely through a special funding allocation) each contributed 38.75 per cent of the cost of these works. The six constituent councils, I am advised, contributed the remaining 22.5 per cent.

I am also advised that the flood protection standard provided by the Bruce Eastick Dam and the South Para spillway works are not providing the level of protection that was originally planned for. This is in part due to levees around Virginia not being originally constructed due to cost and also in part due to recent changes in our understanding of the hydrology of the catchment.

The authority commissioned a further study to investigate what options, if any, are available to raise the flood protection standard to the desired one in 100-year level. This study has recommended either enlargement of the Bruce Eastick Flood Control Dam, at an estimated cost of $40 million, or the construction of strategic levees at Gawler, Two Wells and Virginia, at an estimated cost of about $19 million. I am further advised that while the levee option is less costly, it is also likely to be less effective in mitigating future flood impacts.

However, in view of the most recent flooding at Virginia, it is clear that further work is likely to be required on other levee options in the Virginia area before the study can be finalised. I am also advised that the Stormwater Management Authority is working with the Gawler River Floodplain Management Authority on future flood mitigation options. With regard to the particular questions that the honourable member asked, I will seek responses to those and bring them back.