The Stormwater Engineer


Image: Morely Ave, Roseberry.

I had a long chat with Dave Grasby, an engineer from Sydney Water today. I took a bunch of notes some of which I put in bold on my note sheet. These are my bold points. So much more than this though…

  • Flood Plan Development Manual
  • Merit Based Selection of Appropriate Land Uses
  • Water Research Lab – Manlyvale
  • Australian Rainfall and Runoff (bible of rainfall determination)
  • Buildings change the “behaviour of flooding”
  • Gardener’s Road creates a dam somewhere
  • 1 in 100 year (e.g.) is a statistical term, but the Annual Exceedence Probablity (AEP) is that there is 1% chance of it happening each year. At around 1 in 20 year flood the AEP stops being a simple inverse of the event frequency, there is an exponential somewhere in there. 1 in 100, 1 in 20, 1 in 200 could all occur in the same year.
  • Public Land should be allowed to flood
  • Contact with vegetation is good because it is a good way of getting nasties out of water, because they get taken up by plants.
  • Riparian Corridors
  • Land use is the game
  • Cement mixer and skip bin truck crashing through the roof of a stormwater channel
  • 2 king tides a year, one usually happens at night, one in the day.
  • Roads = Important considerations for overland flow path and underground stormwater drain design
  • SQID (Stormater Quality Improvement Device) and WSUD (Water Sensitive Urban Design)
  • All the water we need is in the City (Sydney)
  • Dams are really big stormwater harvesting projects
  • Fluvial Geomorphology – how rivers shape themselves over time
  • Flood Mapping
  • We’re not going to be able to divorce ourselves from the way that we are & the desire to control nature. But can we control it better? A little bit of taming mother nature might be important, because “we aren’t about to pull up stumps and quit on Sydney”. Interesting opportunities for new development to learn from the past.


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