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A flood of ideas


 
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Associate Professor James Ball, from the University of Technology Sydney’s (UTS) School of Civil and Environmental Engineering, outlines a new Australia-wide approach to mitigating the effects of floods. Rivers, rainfall and run-of all coalesce in creating floods that consequently become hazards to people and it is the management of those floods that is the basis of the School of Civil and Environmental Engineering’s research. Floods may well be rare events but they disrupt the community and the economic activity within it. They are, therefore, quite significant events and their consequences need to be better managed.
Associate Professor James Ball has been working on a project (Australian Rainfall and Run-off) for some ten years having had substantial federal funding over the last eight years, supplemented by funds from state government, local government and consulting engineering companies. The whole project is managed by Engineers Australia and is geared to produce a document that provides guidance on design flood estimation across Australia. These design flood estimates cross borders and do not change when moving from one political jurisdiction to another, something that does not happen now. The border of NSW and Queensland is one example where the design of drainage on one side of a street is different to the other. Political boundaries in the middle of catchments are also a major problem in the effective management of water. This manifests itself with councils, where one council may be part of an upstream catchment and the other council part of the downstream side. The upstream council has a desire to get rid of the water as quickly as possible, while the downstream council wants to hold the water back from its jurisdiction.
A rise in population has made such disparities more noticeable. One of the ideas behind the formation of the Upper Parramatta River Catchment Trust (20 years ago) was to try to bring all of the alternative management techniques together in order to develop consistency between different regions. The trust set up a series of guidelines that councils within that catchment could then apply in a consistent way. Their on-site detention policy was a case in point. There were a number of issues with on-site water detention but having a clear policy that was the same in all areas of the catchment led to a far better outcome than for every council to have its own on-site detention policy. In Australia quite a substantial part of development is in flood prone areas like Brisbane, so flood management needs to ensure that the hazard of the inevitable floods does not become worse, preserving the economic activity within that flood prone area.
Design flood estimates look at the magnitude of the flood event and the likelihood of it occurring. Urbanised catchments change that relationship. The 1955 Maitland floods had a 1% chance of occurring, a likelihood that is still the same. What has happened though is that urbanisation can affect flood events with a 10% chance of occurring. This is because we have designed ways to get rid of water from roads and gutters and transport it to the downstream catchment outlet, increasing the potential flood event. Once the magnitude of the flood flow has been estimated along with the likelihood of it occurring, risk management approaches can then be applied by agencies such as Emergency Management Australia which have expertise in that area.
Climate change poses a particular problem in that Australia has relatively few examples of really extreme events and our data deficiency in that area does not help in forecasting. The Maitland flood is a 1 in 100 year event because the records only go that far back. There are not enough records for anyone to say with confidence what will really happen in extreme events. Estimating and managing the potential hazards is important. Quite often the cheapest land is beside creeks and rivers so, because it can’t be sold, we site community services like schools and aged care facilities (as in Dungog) in those places even though the young and the elderly are less likely to endure a flood hazard. In one place on Sydney’s northern beaches an aged care facility was placed on one side of a creek and a shopping centre on the other, a potential hazard in a flash flood environment.
The project aims to have substantial portions of the document in draft format to be reviewed by the profession in the middle of 2015, with final release expected in the beginning of December 2015. The relevant ministers will also be having a formal launch towards the end of the year. The project brings a series of diverse opinions together in an attempt to create a coherent vision about flood management. Given that Australia is possibly leading the world through this project, Associate Professor James Ball hopes that the findings of the document can then be enhanced as new techniques become available.
It seems a flood of ideas can lead to better flood outcomes for all.

Associate Professor James Ball was interviewed for A Question of Balance by Ruby Vincent. Summary text by Victor Barry, May 2015.

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