Urban stormwater systems were historically designed to move water away from built up urban areas, using big lined channels and smooth pipes to quickly and efficiently remove this water to prevent flooding and inundation. As roof areas and impervious paving increased the volume of runoff increased and the need for efficient stormwater systems was born.
In today’s regulatory environment, there is still a definite bent toward the hard engineering forms of stormwater management , particularly pits and pipes, mainly because these systems remove the water from the roads and roofs quickly, maintaining safe driving surfaces and minimised downtime of any services or routes.
Stormwater systems (as far as pits and pipes go), were originally part of a combined sewer system, but even when separated, traditional stormwater systems have caused pollution of downstream water-bodies, increased sedimentation, and increases in peak flows when compared to the natural environment, creeks and streams, that the system replaces.
Australia is fortunate to have separate sewer and stormwater networks, in some US cities and in many European cities, combined sewers are still a reality, with combined sewer overflows, in some places up to 5-20 times a year, presenting environmental and health risks. Construction of offline storage and maximising the efficiency of the existing network are often cost effective solutions to manage combined sewer overflows.
Typically, stormwater that has been conveyed from the source to the receiving water without any treatment is polluted, often by the accumulation of sediment within the stormwater pipes and on the catchment surfaces between stormwater events. Research has shown that this is a major cause of receiving water pollution.
Now, don’t get me wrong, we will rarely be able to design, meeting regulatory standards, without pits and pipes, but by acknowledging the problems and thinking beyond piped systems, the outcomes might just serve the community and the environment. Despite what the corporations and governments would like you to believe, people do have an interest in what happens to their resources, be it water, waste, stormwater, (probably not so much with sewer though). So being able to include some land usage and natural flow paths if possible would improve environmental qualities of the stormwater, and would improve the aesthetics for the community.
Rejuvenating existing engineered systems can be difficult, and often requires a detailed flood and channel modelling regime to be undertaken. Land may need to be acquired or shared-uses investigated, car parks, playing fields and other open spaces can be used for extreme event storage if designed properly and the catchment permits a safe level of warning to users of the facility.
Recently, I’ve seen hard engineering solutions presented to, and even suggested by, local councils where the best outcome would have been a softer design. It’s as though softer, more environmental designs are treated as second class answers when it comes to simple stormwater conveyance, runoff and flood protection measures. Perhaps the level of development should be considered in greater detail at an earlier stage of any project to ensure that lot yields are realistic within the natural drainage creek and catchment network. Once the network is in, it is very difficult to return to something resembling a natural system. As designers we should encourage each other and clients to see the big picture with stormwater, it’s not just something to get rid of, but provides visual and aesthetic amenity for the future residents, as well as supporting a natural ecology in creeks, ponds and wetlands.
I’ve got more to say on this, and that’s part of what this blog is all about, please check back for more, or subscribe to our feed.