Prevention of the next potentially disastrous flood

Connecting Brisbane River to Logan River

Two possible routes for canals between the Brisbane River and the Logan River are being considered. More work is needed on this with better survey information than I have available at the moment.

The first to consider starts at Goodna on the Brisbane River and essentially goes south following a tributary for about 12 km then cuts across Oxley Creek and joins a tributary of the Logan River. Another possibility is to construct it just west near Round Mountain but it seems that the ground there is too hilly and would make for too much excavation.

The second route is from the bend in the Brisbane River at Fig Tree Pocket. This joins up with Oxley Creek for about 7 km then crosses over bare ground for about 4 km to join a tributary of the Logan River from Algester to Woodridge, then it goes into the Logan River.

The advantage of either of these connections is that it takes a load off the Brisbane River. The biggest disadvantage is that the extra load on the Logan River has to be addressed. Some work may be needed on the water-way between Logan and Beenleigh. Another disadvantage is that in the longest alternative there is about 10 km of new ground to be cut and the river tributaries and creeks will need to be deepened. Furthermore, it is yet to be demonstrated that there is enough slope for the canals to operate efficiently. The Fig Tree Pocket connection will give only partial relief to localities up stream such as Jindalee.

Straightening the Brisbane River

This may not be popular with people at certain locations along the river. Straightening the river will allow it to flow faster. When the water gets away more quickly there is less flooding. Of course, much depends on the tides as well. To maintain the beauty of the river the canals for shortening the river could be gated so that the shortening could be controlled time-wise.

Canals for shortening could be at:

• The Oxley Creek junction with the Brisbane River, near Lake Manchester, to the north-west;
• Across Kholo Road;
• Across the end of Somerville Road, Karalee;
• Across Priors Pocket;
• Graceville to Fig Tree Pocket;
• Across Long Pocket;
• Vulture Street to Dutton Park; and
• Kangaroo Point.

It must be noted that the Brisbane River is an entrenched river and was a canyon during the last Ice Age. Unlike normal meandering rivers it has cut deeply through some tough rock (when the sea level fell). Putting canals across some parts of the river could be an expensive business from the engineering point of view.

At Kangaroo point, for example, the banks are high so it would probably be better to put a short tunnel across it than a canal. This would alleviate the need to put a bridge over the canal.

A full study needs to be made to access the relative value of straightening the river in alleviating floods.