It never drains when it pours

Barry Carter, Dean Watts and Stuart Joyce.


Climate change will bring about more frequent and severe flooding in urbanised areas. In low lying areas sea level change is already having an impact on the performance of piped stormwater systems and sedimentation of waterways and harbours is choking outlets. Existing piped stormwater systems were generally designed for events less than 10 year ARI. In addition inlet capacity is limited due to lack of design or blockage. Aging piped systems suffer root ingress and defects limit their performance. The outcome is that piped stormwater systems are frequently surcharging even during events they were originally designed for and this situation is likely to become significantly worse due to increasing imperviousness, climate change rainfall, sea level rise, aging infrastructure and limited funding. Much greater attention is needed to manage overland flow on roads, through private property and via waterways to cater for severe storms. This paper sets out to provide an overview of the above issues and impacts and propose practical ways to better manage overland flow and minimize reliance on piped systems by a combination of sound geospatial knowledge of the system, well integrated design, land use management and optimisation.

Examples of practical solutions will include:

  • Obtaining and utilizing geospatial information to understand stormwater systems and issues.
  • Establishing prioritized programmes to undertake assessment of flood risks and management of assets.
  • Identifying, avoiding and mitigating overland flow issues when planning and carrying out land development.

Jennifer Howe

Digital Content Manager