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Thursday, 3 May 1973
Page: 1724

Mr KERIN (Macarthur) - In the second reading speech on this Bill the Minister for the Environment and Conservation (Dr Cass) made it clear that this legislation is only to enable assistance to be provided for work on 3 creeks flowing into the ocean south of the Tweed River. The 3 creeks were inadvertently left out of the proposals submitted by the New South Wales Government in 1970. The Commonwealth's contribution is $105,000 and the amount to be spent overall is more than $250,000. I understand that the works will be concentrated on drains and levee construction. I do not have as close a knowledge of these creeks as does the honourable member for Richmond (Mr Anthony) although I can remember spending many happy weeks on the Clarence looking at the flood mitigation scheme. The Minister for the Environment has stated that there is no intention to vary the Act or its method of operation, but the opportunity to say a few words on flood mitigation in general should not be let pass.

The 3 creeks are a part of a progressive submission from the New South Wales State Government and, as honourable members are aware, that is the State which is responsible for the design works and the nomination of these projects, in conjunction with the relevant local authority. Funding is shared by the 3 levels of government. The scheme is a good example of what can be achieved by cooperation. There have been 2 programs of Federal aid. The first was for the 1963-69 period and the second for the 1969-76 period. One of the rivers prescribed in the Act is the Shoalhaven which is in my electorate and in which a close interest was taken by the former honourable member for Macarthur. The Commonwealth contribution to the mitigation of floods in the valley of the Shoalhaven will be of the order of $1.7m by 1976. A conference on flood mitigation will be held in Nowra on 15th May and 16th May and I anticipate that new proposals for measures of government assistance will come from its deliberations.

The scheme has been successful in the Shoalhaven valley but there are some measures which will greatly expand the effectiveness of that scheme at little cost. I think they should be canvassed on this occasion to ascertain the possible value of such measures to the other prescribed river floodplains in the scheme. The maximum time for inundation of the floodplain of the Shoalhaven with major floods is about 5 days with the remaining water after that time being present only in the semi-permanent back swamps. The morphology of the floodplain and the construction of flood mitigation levees and protecting rock banks is such that large basins are now protected from other than the so-called 50 year flood and internal water catchment in the basins themselves. The floodplain of the Shoalhaven contains 11 swampy areas or basins and some of them can now readily be brought into greater production by the use of large capacity vortex or radial pumps to discharge rapidly accumulated water and internally collected water. It will also prove economic to use pumps for the discharge of water associated with minor floods by using pumps associated with existing works. With accurate and predictable water removal control the lower lying areas become particularly attractive for crop production and pasture usage.

This seems to me to be a logical extension of flood mitigation schemes and, as drainage is very much allowable under the terms of the Act, it would appear that if the State Government agreed to these proposals the Commonwealth could not refuse. I am very sure that exceptionally favourable benefit cost ratios will be found for many of the present semipermanent swamp areas of our flood plains if they can be drained. I fully realise that wildlife would have to be taken into consideration with some swamps on the floodplains and in regard to some of the prescribed rivers. But there are just as many other areas in which this consideration would not apply. n small drainage union of land holders on the Shoalhaven flood-plain has already demonstrated the economics of a small vortex pump but it is beyond their ability to raise the capital for a pump for the larger swamps. One farmer recently gained $35,000 by producing rye grass seed on what formerly was swamp. The water table in this area is generally 2 feet below the usual level in the drains. The Shoalhaven Shire Council, which is the administering authority in this area, has been carrying out surveys into this matter and the preliminary results have been very favourable. Local farmers have already demonstrated that pasture species with a high tolerance to water can be established provided the water can be removed within a period of days beyond the major inundation period. Water couch, for example, can stand inundation for one to two months at certain times of the year. The sort of pumps we have in mind would have to be capable of discharging about 180 cusecs. It has been estimated that a pump of this sort would cost about $46,000. The productivity of dairy farms adjoining the swamps would be greatly increased and, in view of the fact that there is a dairy reconstruction scheme operating in Australia, it can be argued that a small outlay of Commonwealth money on one farm would increase the average living area of the farm, thereby increasing more viable farming units.

The other major area of flood mitigation which could well merit further investigation with a view to a logical extension of the scheme centres on the neglected state of river estuaries. The State governments are limited in the work that they can do to construct breakwaters to prevent sand drift and silt accumulation in the delta. The Shoalhaven Heads, for example, used to provide an escape for the waters of the Shoalhaven but now only open for a major flood. The opening of the heads and the construction of a breakwater at this point would greatly mitigate the effects of flooding on the flood plain as there have been situations in which the level of the blockage of the heads has determined the level and the consequences of the flood. For example, the pushing of water up Broughton Creek is entirely dependent on this. Although each flood-plain has its own morphology it seems to me that this aspect of mitigation should be more closely examined. Shoalhaven Heads has now become Shoalhaven Bay and it will shortly become Shoalhaven Flat unless some work is undertaken in this area. I commend the amending Bill to the House and I trust that logical extensions of the scheme will be reviewed when they come forward.

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