Mr DUNHAM - 1998-02-17
I am very familiar with the town of Katherine and the levels the 1957 flood reached. As a public servant in the town, I attended counter disaster meetings at which we tried to anticipate the impact of floods and to predict the maximum flood levels. Like all other members, I was shocked at the height last month's flood reached and the speed with which the water rose, and the subsequent human and economic costs. What is the likelihood of a flood of this magnitude being repeated and what measures are being considered to reduce damage from further floods?
ANSWER
Madam Speaker, it is unfortunate that it requires events such as the recent Katherine disaster to provide us with a closer and better understanding of the environment in which we all live and work. One of the challenges facing the government, following that disaster, is to determine what we can learn from it and how best to go about planning for the future. My department has employed a consultant hydrologist to advise the government on the extent of the flood. He is working there in conjunction with officers of my department.
While that engineering work will continue for some time, preliminary estimates indicate that the recent flood in Katherine was something between a 200-year and 500-year return event. To give some indication of the magnitude of the flood, the peak flow rate was 12 000 m3/s which is about 2.5 times the volume that was experienced in the 1957 flood. A flow of that rate would completely fill an empty Sydney Harbour in 12 hours. Closer to home, it would fill Manton Dam in 20 minutes. The flood volume is estimated to have had the capacity to fill Sydney Harbour at least 4 times. It is also estimated that 250 km2 of land was flooded in the
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immediate Katherine area, and 2000 km2 to 3000 km2 of land in the entire Daly River catchment.
Generally, planning is based on a Q100 level - a 1-in-100-year return flood. That has been an Australian standard since the early 1970s. However, following this event, it is possible that the level will be revised and raised from Q100 in the future. As I said, we have implemented engineering studies and, following their completion, we will be better able to assess what we need to do. Measures such as the construction of levee banks, flood-mitigation dams, flood warning systems and evacuation systems will all be examined closely to determine what improvements need to be made, or what new works need to be constructed. However, it would be both foolish and irresponsible to make snap decisions in the absence of all the detailed engineering studies that need to be undertaken.
The Department of Lands, Planning and Environment currently has a set of land-use objectives for the Katherine area almost completed and ready to be published. In view of the recent event, obviously this will be delayed. What we need to stress is that events such as the Katherine flood are extreme in nature and it is impossible to protect fully all persons or all property against such events. However, we will review our floodplain management policy and attempt to ameliorate the impact on Katherine of future events.
I table a preliminary hydrology study undertaken by Kinhill Engineering and a map produced by my department on the extent of flooding in the Katherine. The light blue markings indicate the previous 1-in-100-year flood level, and the darker blue markings show the extent of the Katherine flood to the area that we have mapped so far. Large areas of the town, especially in Katherine South, were previously believed to be outside the 1-in-100-year flood level, but were seriously inundated in this latest flood. As I said, the government will learn from this event and will plan properly for the future. However, it is not a time to make snap judgments or hasty decisions. It is a time to assemble the information properly so that we can plan for the future.
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ANSWER
Madam Speaker, it is unfortunate that it requires events such as the recent Katherine disaster to provide us with a closer and better understanding of the environment in which we all live and work. One of the challenges facing the government, following that disaster, is to determine what we can learn from it and how best to go about planning for the future. My department has employed a consultant hydrologist to advise the government on the extent of the flood. He is working there in conjunction with officers of my department.
While that engineering work will continue for some time, preliminary estimates indicate that the recent flood in Katherine was something between a 200-year and 500-year return event. To give some indication of the magnitude of the flood, the peak flow rate was 12 000 m3/s which is about 2.5 times the volume that was experienced in the 1957 flood. A flow of that rate would completely fill an empty Sydney Harbour in 12 hours. Closer to home, it would fill Manton Dam in 20 minutes. The flood volume is estimated to have had the capacity to fill Sydney Harbour at least 4 times. It is also estimated that 250 km2 of land was flooded in the
Page 4
immediate Katherine area, and 2000 km2 to 3000 km2 of land in the entire Daly River catchment.
Generally, planning is based on a Q100 level - a 1-in-100-year return flood. That has been an Australian standard since the early 1970s. However, following this event, it is possible that the level will be revised and raised from Q100 in the future. As I said, we have implemented engineering studies and, following their completion, we will be better able to assess what we need to do. Measures such as the construction of levee banks, flood-mitigation dams, flood warning systems and evacuation systems will all be examined closely to determine what improvements need to be made, or what new works need to be constructed. However, it would be both foolish and irresponsible to make snap decisions in the absence of all the detailed engineering studies that need to be undertaken.
The Department of Lands, Planning and Environment currently has a set of land-use objectives for the Katherine area almost completed and ready to be published. In view of the recent event, obviously this will be delayed. What we need to stress is that events such as the Katherine flood are extreme in nature and it is impossible to protect fully all persons or all property against such events. However, we will review our floodplain management policy and attempt to ameliorate the impact on Katherine of future events.
I table a preliminary hydrology study undertaken by Kinhill Engineering and a map produced by my department on the extent of flooding in the Katherine. The light blue markings indicate the previous 1-in-100-year flood level, and the darker blue markings show the extent of the Katherine flood to the area that we have mapped so far. Large areas of the town, especially in Katherine South, were previously believed to be outside the 1-in-100-year flood level, but were seriously inundated in this latest flood. As I said, the government will learn from this event and will plan properly for the future. However, it is not a time to make snap judgments or hasty decisions. It is a time to assemble the information properly so that we can plan for the future.
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Last updated: 09 Aug 2016