In Victoria in late 2010 and early 2011 most water catchment systems
experienced the highest inflows recorded since 1993, as a result of a
series of high rainfall events. The resulting floods were widespread
over central and northern Victoria, and had a significant impact on
urban communities, agricultural areas and the natural environment.
Between September 2010 and February 2011 G-MW experienced flooding
across most of its operating regions with record flooding in both the
Loddon and Campaspe catchments. The floods covered some 16,000 square
km of G-MW's service region, with approximately 3,000 km of its
channel network affected. Infrastructure was damaged and recreational
areas were affected by floodwaters.
G-MW customers, staff and communities in our service area were all impacted in some way by the damage caused by these events.
Why Did the Storages Spill?
G-MW manages 16 large dams across Northern Victoria. By late 2010
most of the dams managed by G-MW were full as a result of winter and
spring rains. As further heavy rainfall events occurred, stormwater
runoff caused flooding in the upper catchments which flowed into the
dams. These floods were passed through the dam spillways.
What is the Purpose of the Storages G-MW Manages?
G-MW's storages are designed and operated to harvest, store and
release bulk water for downstream entitlement holders. The dams are
neither intended nor designed to be used for flood mitigation purposes,
although G-MW operates the dams to reduce flood impacts where possible.
Managing Floods Through Dams
G-MW dams are operated in accordance with flood operations
procedures which comply with the requirements of the bulk entitlement
orders. The bulk entitlement orders provide conditions under which G-MW
can release water from dams; there is no scope given to release water
from a dam for flood mitigation purposes except for Lake Eildon.
However, where G-MW can be reasonably assured that a pre-release can
be made without adversely impacting on water resource availability then
pre-releases are made from dams with gated spillways (Eildon, Cairn
Curran and Buffalo).
Pre-releasing water from full or near-full storages will only be
effective for relatively minor flood events, and must be managed so as
to not aggravate flooding further downstream. During each of the 2010/11
flood events, water was pre-released from Cairn Curran.
Throughout the flood events G-MW maintained regular contact with
VICSES, local government and the Bureau of Meteorology to provide
operational advice to the flood response efforts.
How did the Flood Impact on G-MW Assets?
Once the scale of the predicted weather event and its likely impact
on G-MW's systems was evident, G-MW staff worked long hours in
co-ordination with other agencies under very trying circumstances to
ensure that impact of the flood water was reduced for the whole region,
and to minimise damage to G-MW assets.
The floods impacted on three key storages controlled by G-MW -
Laanecoorie and Cairn Curran Reservoirs (both Loddon system), and Lake
Eppalock (Campaspe system). Tullaroop Reservoir was impacted to a lesser
extent.
During major floods, G-MW shuts down the irrigation channel network
by closing regulating structures. This allows overland floods to follow
natural flow paths and aims to prevent flood water being transferred
along channels and affecting other landowners.
G-MW's channel systems were significantly affected by the
flooding, with many of the earthen channel banks washed away. Some road
bridges owned by G-MW were destroyed and the G-MW customer centre in
Rochester was also flooded.
Providing Assistance
It is the role of the VICSES to provide flood emergency management
co-ordination as a lead agency. The Bureau of Meteorology's (BoM)
role is to monitor river levels and issue warnings as appropriate to
G-MW, SES, local shire councils and through media networks to the
public.
During flood events G-MW's role is to communicate with these
agencies to provide regular information on releases from G-MW's
storages. This arrangement is in accordance with the current Victorian
Emergency Management Manual.
Working with Other Agencies
In the lead up to increased flows in January 2011 G-MW contributed
to an overall flood mitigation strategy for the Kerang Lakes region as
well as releasing water from key storages in the area, including:
- Diverted water via irrigation channels near Kerang into Lake
Tutchewop, with the approval of the Murray-Darling Basin Authority
(MDBA)
- Under the direction of the Municipal Emergency Response
Coordinator (MERC), G-MW's Number 9 channel was banked off during the
flood threat on Swan Hill to prevent water from flowing into town, the
Number 10 channel bank in the Tyntynder flats area strengthened and the
14/2 channel bank incorporated with the Town Levee to assist in the
protection of the Kerang township.
- Under the direction of the Regional Incident Control Centre
(ICC) in Bendigo, G-MW resources completed urgent inspections on the
Kerang town levee and participated in various planning activities.
- Worked closely with the ICC to ensure that all possible avenues
were explored to relieve some of the pressure on storages and channels
from the rising floodwater to minimise impacts on the community.
Helping Customers
G-MW immediately started a program of assistance for flood-affected
customers. G-MW extended account payment deadlines and provided
replacement statements. Information about assistance from Government and
other agencies was given and G-MW created a dedicated web page with
up-to-date flood status and recovery information. G-MW also provided
input to government planning on flood recovery assistance programs. In
addition G-MW's Water Wheels Information Van toured the region and
G-MW gave regular updates to DSE and the Government to help develop
flood recovery assistance.
Recovery
G-MW has repaired or replaced damaged infrastructure and public
recreation areas. Dam gates have been repaired or replaced at
Laanecoorie, channel banks reinstated and recreation areas cleaned up
and repaired. The G-MW office in Rochester has been refurbished with
most of the flood damage to the interior of the building repaired.
At 30 June recovery work on channels was 95% complete, with some
small areas of channel rectification to occur before the next irrigation
season commences.
Following the floods, one of the main issues for the business was
the 40 degree heat after the January rain. While some areas were
flooding, others required water for irrigation again within days.
Repairing channels in order to use them for water supply was a
logistical challenge for G-MW. Many staff resources were diverted to
assist the recovery effort, including diverting staff from other
centres, construction crews and asset assessors to walk channel banks
and identify where repairs were needed. External contractors were also
engaged to allow repairs to be carried out quickly and efficently.
After the floods, G-MW staff also assisted local councils to
identify areas where flood water had ponded, and provided resources to
help move it on, particularly in the Benjeroop area.
Moving Forward
Following the January 2011 floods, G-MW attracted considerable
criticism from the media and community for perceived inappropriate
action in relation to flood mitigation at, in particular, the Cairn
Curran and Laanecoorie dams, and Lake Eppalock. This has highlighted the
need for further community education on the design, and role of the
storages G-MW manages in relation to flood events and the need to
reinforce the role of each agency in relation to flood warnings and
information updates.
A preliminary internal review has been undertaken, and G-MW is
confident that appropriate procedures were followed throughout the
incident, and that those procedures remain valid for future safe
operation of our assets. G-MW also identified that:
- Forecast information from the BoM was consistent with similar information provided in previous flood events.
- Flood level scenario modelling provided by BoM was helpful to gauge the possible severity of the event.
- Some improvements could be made to streamline internal and external communications.
- Current level of personnel resourcing for dams operations is
adequate to manage significant flood events. 24 hour operating flood
rosters were implemented during each event. Rostering staff rest breaks
was challenging, but generally was managed.
- Staff isolation at various sites was anticipated and well managed.
- Significant public interest at storages created some challenges with public and traffic management.
- Co-ordination with the ICC was adequate, and mainly maintained
through regular situation reports and periodic telephone calls. In
future events, G-MW will offer to have a liaison officer embedded at the
ICC.
- Engaging with the public to increase awareness of the
possibility of flooding was difficult prior to the November 2010 event,
especially amongst new members of the community. Following the event
there was significant interest from downstream communities.
- G-MW experienced significant demand for information updates on
flood issues that were unrelated to the operation of our infrastructure,
as well as increased requests from landowners to operate irrigation
infrastructure to divert floodwaters.
Flood events on the scale of November 2010 and January 2011 are
rare (likely to be only one in 100 years). G-MW's operating procedures
had never been tested under these conditions. G-MW is engaging an
independent review of the dams operating procedures and the use of those
procedures during these two flood events. The review is scheduled for
completion in September 2011.
