Alice Springs a flood disaster waiting to happen

I visited Alice Springs last week to deliver a paper on risk management at a business forum. In preparation for this I was interviewed by the local newspaper and spoke about my thoughts on the risk of flood.

On my arrival into town it was clear that the risk was much greater than I thought and so over the weekend I wrote a follow up piece to the paper in the hope that the issue is addressed before the inevitable happens.

I did this as I have been attending natural disasters for over 40 years and with the benefit of hindsight much of the loss of life and property losses could have been avoided by basic risk management strategies.

Having visited Alice Springs since the early 1980’s it  genuinely shocked me to see the level of the Todd River come up so much and the relatively recent proliferation of trees in the river bed itself.

I came to the topic with open eyes, an open mind and two very open ears to hear from the community. I was greatly heartened by elders of the local community and also by settler families of longstanding voicing their complete support for what I was saying.

What is clear to me, supported by photos taken in the 1920’s and 1930’s that were brought along to the meeting,  is that the river naturally had high river banks, estimated at between 4 and 5 metres. This was self-dredging during periods of heavy rain.

The following photographs were provided to me during the meeting. These show the Todd River with water in it but with no flooding, no trees and a definite river bank.

Since that time, a great deal of development has occurred on either side of the Todd River and the hard surfaces of roofs and streets collect and direct the water into the river where much of this would have been absorbed into the ground.

Much worse to my mind has been the introduction of so called bridges across the Todd River. I enclose a photograph below of one which highlights the problem.

The bridge is really a number of concrete pipes that have been placed on the river which act like a dam holding back the sand so that it no longer self-dredges. As a result the height of the sand has increased by somewhere between 4 and 5 metres.

Further trees have been allowed to grow in the river bed. I saw dozens that had fallen down in a 100 metre stretch in front of the
Crowne Plaza. One can be seen in the above photograph. These trees will be swept along in the next flood only to be caught by the bridge which has not been designed to allow them to pass and the pile of dead trees and fallen limbs will act as a dam holding back the water.

This problem has been exacerbated by the installation of a strong thick pipe hand rail along the length of the bridge. This 100mm pipe rail can be clearly seen in the photo above.

This replaced a rail that was designed to collapse during a flood and let the water and trees pass over. The new rail will now be held back to a higher level.

As residents of Alice Springs are acutely aware, the vast majority of Alice Springs homes and businesses are built on concrete slabs at ground level. It is man’s intervention that has caused this problem.

I genuinely believe that this is a disaster waiting to happen and while it may not happen tomorrow, it will happen.

The way to fix the problem really starts with correcting the design of the bridges. If this is too costly then work needs to be done to remove the trees, tree limbs and other debris that will dam the river and lower the level of the Todd River so that as much water as possible stays in the river and does not flood.

All of this costs money but what is the price of a single life or the huge financial and psychological impact on the families, businesses and community as a whole if this work is not done?

Many towns face this sort of problem and evaluating the risk of all natural perils should be top of mind for engineers and town planners. Simple things like the bridge rail should simply not occur.

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