Lower Murray reclaimed irrigation areas flood recovery

Recovery priorities

Re-establishing the levee network and returning agricultural land to production as soon as possible is a priority recovery activity. A coordinated program to assess and stabilise levees and undertake dewatering of inundated land is underway.

Lower Murray Reclaimed Irrigation Area (LMRIA) recovery activities, including levee assessment and stabilisation and dewatering, applies equally to government and privately owned levees. PIRSA is leading targeted community engagement with key industries and primary producers in high impact areas though regular communications, landholder meetings and direct liaison. The Department for Environment and Water (DEW) is working with engineers and landholders to undertake levee assessments and look at what repair solutions may be feasible once on-ground works are possible.

In many areas the stability of the levee is unknown until an assessment is complete. The safety of staff, contractors and landholders is our highest priority, and we cannot undertake works until it is safe to access the levee. This is a complex operation requiring significant cross-government collaboration and a lot of work has occurred to date to get to this point.

Due to the complexities involved, a comprehensive engagement process is underway aimed at not only assisting our producers to understand each stage of the recovery process but for us to ensure the unique needs of each irrigation area is addressed in the recovery planning.

LMRIA recovery subcommittee

The LMRIA Recovery Subcommittee has been formed to ensure the flood recovery priorities for primary producers are appropriately represented and is providing effective two-way communication between community and government. The members of this subcommittee include Irrigation Trust representatives, community representatives and representatives from Department for Environment and Water (DEW), SA Water, Murraylands and Riverlands Landscape board, SA Dairyfarmers’ Association (SADA). Community members raise matters to be discussed through any of these members.

Levee assessment and stabilisation

LiDAR (Light Detection and Ranging) is a remote sensing technology that uses laser pulses to create 3D models of surfaces. It is used for levee breach assessments to provide accurate and detailed topographic information for flood risk analysis. For levee condition assessments, mapping data collected via aerial surveys is used to assess initial damage to levees from flood waters.

LiDAR flights and data have been completed for all levees, and stability assessments and reports have been completed for government owned levees. DEW is currently working with the LiDAR surveyors to develop LiDAR profiles for each levee which can then be provided to landholders. Short-term stability works, where required, have either commenced or are complete to enable dewatering.

Early planning and revisiting of sites have started for the intermediate stabilisation of levees to support levee function and help with protection from wind seiche and fluctuating river levels during normal river operations. Once intermediate works are complete and the areas have dried out, a full condition assessment will be undertaken to determine longer term requirements.

DEW and SA Water are currently working to maintain an average water level of 0.7 m AHD across Lake Alexandrina and Lake Albert. Although this is the target, there will be times when the water levels can be higher or lower. At these times the barrages will be operated to either raise or lower water levels as required. Water levels and barrage operations are monitored closely by the South Australian Government, Murray-Darling Basin Authority and Commonwealth Environmental Water Office.

Dewatering program

The process of removal of water from inundated properties is underway. There are 26 irrigation areas in the LMRIA involving 142 landholders. Twenty of these areas supporting agriculture production were inundated by the flood and require assistance to dewater and recover.

Dewatering commences where:

• the area is safe to access with heavy vehicles
• the breach or overtopping area is no longer below water level
• the flow of water into the irrigation area has ceased
• no stabilisation works are required to the levee
• vehicle access to the levee is not required for pump placement and operation
• the appropriate equipment is available.

PIRSA in partnership with SA Dairyfarmers’ Association (SADA) is conducting the dewatering process within existing regulatory requirements and with full consideration of environmental aspects such as water quality, pest species management, river and levee bank protection. The risk of water quality issues resulting from the dewatering process is low while river flow rates remain high. A water quality monitoring protocol is in place.

Post-flood soil management and weed support

The Murraylands and Riverland Landscape Board’s district officers provide support to landholders, shack owners and primary producers by helping to identify potential weed species and provide advice about available control options.

Landholders are encouraged to be on the lookout for emerging weeds, including unfamiliar weed species which may have travelled down river via flood waters.

The benefits of this support include:

• free equipment loan
• herbicides
• control services
• advisory services.

To arrange a property visit from a district officer, contact the Murray Bridge office on (08) 8532 9100.

See Post flood weed support for more information.