Inquiry into flood mitigation infrastructure in Victoria Submission no.6 Lake Boga Vic. 3584 23rd July 2011 The Chairman Inquiry into Flood Mitigation Infrastructure in Victoria Dear Mr Koch, Herewith, I offer a submission to your enquiry which includes items I hope will be acted upon after you deliver your report. I also hope my submission and remarks give additional information to help you arrive at your conclusions. Now retired, I once conducted woolgrowing activities in the Tresco – Mystic Park area. I have lived at Tresco over 72 years, have experienced three major floods in that time, and know the Benjeroop, Mystic Park, Lake Boga region well. It is the Avoca River, terminating in this area, with which I am particularly experienced. All remarks and recommended works for the Avoca Outfall are based on experience and knowledge of the flood characteristics of that area of the river. The latest 2011 flood, considered the greatest since European settlement, was carried by existing infrastructure of the Outfall channel past Mystic Park, but its disposal beyond that township was poor because of much needed works and improved management. Below, is my resume of the past and present situation of this river and lakes system, followed by a list of works urgently required to safeguard against future damage in the control of floods. Yours faithfully, John Jobson The Avoca, Loddon and Murray Rivers in the region north of Kerang. Three rivers in flood (the Avoca, Loddon and Murray Rivers) reach this region and converge in one general area (Benjeroop, Winlaton, Fish Point, Lake Boga) before proceeding past Swan Hill in one river – the Murray. Adjacent to and within this river system, are the Kerang Lakes, which usually are supply lakes for irrigation. In flood times these lakes serve as flood relief and buffer zones in the control of the Loddon River. Manipulation of Loddon flows usually involves running high volumes through the Kerang Lakes system, in addition to the normal river flow toward Benjeroop to join the Murray River. Managing floods from the Avoca River always adds to the problem of managing Loddon River floods into an already swollen Murray River, because extreme levels reach the region at differing times. The Murray is already running at high levels when a Loddon flood arrives, and from one to three weeks later, Avoca River floodwater emerges from the Mystic Park Marshes. Avoca floodwater then flows along the man-made Avoca Outfall channel toward the Murray Valley Highway. The disposal of Avoca River floodwater beyond Mystic Park can have great bearing upon the local area and management of the Loddon/Murray flood levels. A major lake (Lake Tutchewop) was taken out of the system in 1968, to become a saline water disposal basin. During the recently experienced major drought, Lake Tutchewop became dry until the 2011 flood, when emergency measures demanded it be used to aid flood control. Before 1968, Tutchewop was used extensively to aid in flood control of the Avoca River; thereby aiding overall control of Loddon River floodwater. Lake Tutchewop should be returned to its original natural use for flood mitigation. In past floods, flood flows in the Kerang – Swan Hill region were controlled by one authority - the SR&WSC. That water authority has now been superseded by Goulburn-Murray Water. This current water authority should remain as the one authority in control of the flood flows, because of the somewhat juggling act needed to balance the overall problem of three rivers coming together. Outside interference from other government departments attempting to influence flood control by this one authority (Goulburn Murray Water) must be avoided. The newer generation of local Goulburn-Murray Water senior personnel need to consult much more with local flood wardens and farmers regarding management of floods through the Kerang Lakes. The 2011 flood showed the department’s great ignorance to manage the lakes prior to any floodwater reaching the region. Had a strategy known to flood wardens and farmers been implemented, better Loddon flood control would have resulted and Benjeroop possibly not been subjected to such great inundation. This problem is an example of the newer generation of authority personnel being inexperienced and unwilling to seek sound advice from reliable sources. Government department attitudes need to be changed as well as procedures. _____________________ To: The Chairman. The Inquiry into Flood Mitigation Infrastructure in Victoria The Avoca River Mystic Park Marshes to the Murray River. Important points needing consideration as a result of January 2011 floods, to safeguard against future floods. The writer considers points 1, 2, 3, & 5 marked with a red asterisk to be of great importance. Suggested works. *1. The levee bank at north end of Mystic Park Marshes. * This levee bank needs strengthening, 45 cm additional height and regular maintenance. * Immediately close breach in above levee bank caused by ignorant officials during the flood. Avoca floodwater reaching the marshes from Quambatook naturally flows in a north- easterly direction toward the Mystic Park forest and Lake Tutchewop, thence to the Murray River. In early times during extreme floods, Avoca River water combined with Loddon River water at the western side of Kangaroo Lake, to create an inland sea about Mystic Park, eastern Tresco, Lake Boga, Winlaton and Fish Point. Under natural conditions, Avoca floodwater had no defined route to the Murray River beyond Lake Bael Bael and the Mystic Park marshes. The Avoca Outfall channel was constructed in the early 1930’s to stop local flooding and deliver water from the marshes to Lake Tutchewop. The outfall channel is the final route of Avoca floodwater for disposal into Lake Tutchewop or the Murray River via a large water channel. A levee bank at the north end of the Mystic Park Marshes was placed there many years ago to control the Avoca River and Yassam (Back) Creek. The bank is on privately owned land and was regularly maintained for some 50 years by a former property owner. There has not been a flood in the marshes, and maintenance has not been done on the bank, since about 1996. This strategically positioned bank acts to contain Avoca River floodwater within the Marshes. It also allows storage of greater quantities of floodwater. Discharge of water from the marshes via the Outfall channel can then be managed in conjunction with the Loddon and Murray rivers. Some form of management control and maintenance needs to be exercised by an authority over this levee bank to safeguard Mystic Park, aid local lake and river flood management, and avoid potential flood threat to the Tresco horticultural district and Lake Boga. Without this levee bank, uncontrolled Avoca water would create havoc in flood management in this area. A breach was made in this bank during the recent flood, by ignorant authorities, in a mistaken idea to “spread the flood.” Fortunately, the breach was made where water would not flow anywhere, and did not cause damage to anyone. This bank should never be interfered with in future, as it is most important in flood control within this area. This bank needs to be left where it is and not interfered with in future floods. It only requires improvement and regular maintenance. _________ *2. Remove Lake Tutchewop from Barr Creek salinity interception scheme, and use exclusively for Avoca River flood relief. Lake Tutchewop was originally the Avoca River terminal lake until 1968, when it was taken over as an evaporative basin for disposal of saline water from the Barr Creek. The Barr Creek changed from being a freshwater creek, to become the largest single source of salinity entering the Murray River, after water authorities made the creek into a drainage channel for the Cohuna district almost a century ago. With the re-arrangement of irrigation in the Murray-Darling basin, high water costs, laser grading and water re-use, and other changes to the system, the Barr Creek will no longer be a great source of salinity in future. Environmental flows should be made available into Barr Creek, to guarantee reduced salinity in the creek and the lower Loddon River. Increased Pyramid Creek flows to the Loddon River released from the Kerang weir into the Lower Loddon would further reduce salinity inflow to the Murray River. This would aid farmers living along the lower Loddon, and improve conditions at Benjeroop for potential tourist trade in future. (The Benjeroop Hall Committee is aiming to establish a working historic pump which is presently being restored). Under present changed Barr Creek conditions, Lake Tutchewop is not needed. Climate pattern changes with possibly wetter years will create more frequent floods in this area. Management of three flooded rivers in this area is always a problem. When Lake Tutchewop was taken out of flood relief 49 years ago, flood management became a greater problem. The latest flood made it essential to use Tutchewop as part of management to relieve pressure on Swan Hill and its surrounds. This indicated how important the lake was during past floods, and remains so today in local flood management. I suggest Lake Tutchewop should resume its natural role as the terminal lake for the Avoca River, and henceforth be used only for flood relief. _________ *3. Restore collapsed bridge at outlet of Lake Tutchewop on the Benjeroop-Tresco Road for future flood water escape to Murray River. The outlet bridge collapse at Lake Tutchewop was caused by mismanagement of flood water at a time of high excitement. It needs reinstating to allow water escape from the lake. If Tutchewop reverts to Avoca floodwater relief (which seems likely), the lake will need an outlet to lower its water level for flood relief in succeeding floods.