When water main networks fail it’s often big news as the flow on effects to communities can be significant, including water supply interruptions, traffic delays, damage to infrastructure and flooding of property.
By understanding the likely cause of failures and pinpointing risks across assets, utilities can be more proactive in preventing failures, more targeted in asset renewal, and reduce the impacts to their communities.
A recent project with Hunter Water Corporation in the Hunter Region, New South Wales, Australia demonstrates what can be achieved through innovative approaches to flood modelling.
Pipeline infrastructure
Hunter Water Corporation (HWC) has more than 5000 km of pressure mains in its water supply network. Like all water utilities, occasionally significant water mains breaks and leaks occur that attract community concern and media attention.
For the last three years HWC has aggressively targeted leakage as an area to improve, and investigated where major main breaks could occur that can put individuals at risk in their homes and on roadways.
HWC recognised that with sufficient information, they could proactively intervene to reduce the potential for failure of the highest risk assets. They could also delay scheduled renewal of low risk assets to focus on high risk assets.
In late 2018 HWC approached GHD to consider a solution.
Developing an ideal solution
While the leading industry solution would be to predict the flow direction using topography, and overlay this with road and property data to approximate the effects, this wouldn’t adequately meet HWC’s needs.
Nicholas Deeks, Technical Director – Hydrology, GHD, explains, “The ideal solution was to build two-dimensional flood models that account for the unique properties of each failure location.”
With this in mind, Nicholas tested that the proposed modelling approach could replicate historic events.
“We did this at three sites, and got a good match so we progressed by filtering the data down to assets that are likely to have the highest failure risk. We chose mains over 375 mm in diameter at five metre spacing, which resulted in 57,000 models.”
The project engaged our specialised spatial scientists in Perth and Brisbane, hydraulic modellers in Perth and Manila, and civil engineers in Newcastle. Ultimately, a database of consequences for each water main segment was produced so that HWC could target the high consequence mains for monitoring, renewal or replacement.
“Traditional manual methods used to build each flood model aren’t possible for 57,000 models. So we needed GIS tools and processes to automate the build; topography and model inflows were relatively easy, but hydraulic roughness was more challenging.”
The team developed new methods for estimating hydraulic roughness using a combination of machine learning algorithms, normalised difference vegetation index thresholds, road centerline buffers and classified Lidar data. A similar approach was adopted to derive building outlines.
“GIS processes made the whole solution possible; we created 57,000 model envelopes for each break point, and used these envelopes to ‘cookie cutter’ each of the model variables required to build 57,000 unique flood models. We used TUFLOW software to simulate the flood behavior, and by utilising new, heavily parallel computing methods and six graphics cards we cut the model run time from four years to six weeks.”
An innovative approach
While building and running flood models is ‘business as usual’ for GHD, the method for automating 57,000 flood models is unique and innovative. The approach allowed our client to understand a wide range of consequences and to take preventative action, saving money and addressing community concerns. GHD also benefits from efficiencies inherent to the new methods and automation.
By automating the flood modelling process, including the build, simulation and processing of results, the project is scalable: if a client has 100km of pipelines or 100,000km of pipelines, the method is the same.
The approach can predict consequences to cultural and environmental assets that could be damaged by large flows. This methodology can also be used to predict environmental consequences of oil pipeline failures, or chemical spills occurring on linear infrastructure.
By reducing failures, the community benefits from reduced traffic disruption, reduced water supply discontinuities, reduced damage costs and increased safety.
For more information, connect with our hydrology professional:
Nicholas Deeks
Technical Director – Hydrology, GHD
+61 8 6222 8956
Email Nicholas Deeks
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GHD has a powerful global network of water skills and experience that we can apply to local scenarios. We offer a broad range of services covering feasibility studies, planning, design, project management, construction and asset management services as well as operational optimisation. Our people use selective research, perform pilot trials, fine-tune existing systems and transfer technologies from other industries to improve quality and manage asset costs. www.ghd.com/en/expertise/water