Prevention of the next potentially disastrous flood

Deepening the Brisbane River

The river would run faster if it were deeper. This would help reduce flooding to some extent depending on the tides. When the river was a canyon 12,000 years ago it was about 30m deep. It has since been filling up with sand, silt and mud. Until recently the river was dredged for its sand resources. This has been stopped as it was thought it was muddying the river. It used to be a beautiful clear river in Aboriginal times. There is some doubt now that dredging is the main cause of the opacity of the river. It seems that other factors are more important.

Dredging will help the flow of the river if the dredging is done in the right places. As with straightening the river, we do not know if dredging in the right places will have a major or minor effect. This awaits further study.

The flood potential would also be reduced if the river was widened. This would apply particularly at certain localities where constrictions occur. Any building that constricts the flow should be removed. It exacerbates flooding and is at risk itself.

Relief to the rainfall situation involves a unique suggestion that I made involving the use cloud seeding to prevent the rain reaching the Brisbane catchment area in flood seasons. This should work very well when cloud seeding can be carried out over the sea. Many people do not realise that cloud seeding works, despite having a shaky early history.

Cloud seeding is normally done to bring rainfall to certain areas. The concept here is to use it for keeping rain away from a given area. The usual problem about whether or not the cloud has the potential to rain does not apply here as the cloud is expected to rain anyway. Seeding in this case is to control the time and hence the place of rainfall. Although this is a new concept it is hard to see why heavy rain clouds should not be easier to precipitate than milder clouds in more barren areas.

Cloud seeding has been used successfully in Tasmania since the 1960s where catchment in the dam increased by 30%. "Warm cloud" seeding experiments have also been conducted in Queensland by the Australian Bureau of Meteorology. It is used also used in the Snowy Mountains to precipitate snow.

Furthermore, it also was used at the Beijing Olympics to keep Beijing dry during a rainy season, and it worked. It has also been used in Jakarta late last month to prevent further flooding after 50,000 people were made homeless and early results suggest it has had some success (http://www.abc.net.au/rural/news/content/201301/s3678824.htm).

The only problem with this concept is that it needs proving and can only be really tested in a rainy season.

In conclusion there is no single solution to flooding and several measures should be used together. It is hoped that the government will take note of at least some of the 753 suggestions made to the Commission in 2011 and take account of levee banks that have failed in various parts of the world.

Further study is obviously needed and some ideas may be modified. I would like to see at least one measure for diverting water from Wivenhoe Dam, at least one measure for controlling the Brisbane River flow, and some serious research into cloud seeding to prevent unwanted rainfall over the Brisbane region. I believe the building of new dams is already being investigated.