Storm WaterWaterWater Conservation

Water Management in Urban Areas

Water-Management-In-Urban_areas

Water management in rural areas has always been an issue of great interest. On the one hand, water for human, stock and crop use is critical to living and producing. It is also a major factor in the very visible degradation of streams, the creation of gullies and changes to the natural flora and fauna associated with streams.

The common farm-scale actions of clearing, road construction, ploughing, (over) grazing and draining combine to have catchment-scale impacts. These impacts flow from the greater quantity and speed of runoff water which results in soil erosion (involving sediment and nutrient export) and scouring of stream channels which had developed to accommodate a regime of lower stream flows. Downstream impacts on other waterways can also be important: the 2011 floods in South East Queensland were estimated to have dumped 3 million cubic metres of sediment into the aquatic habitat of Moreton Bay.

In many regions, one of the first responses to increasing environmental concerns has been the rehabilitation of rural streams and catchments. In Australia, many Landcare projects in the 1980-90s related to some element of catchment or stream degradation, and Rivercare type programs flourished in the early part of the 21st century.

Not surprisingly, water management is commonly a primary selection factor in Permaculture designs for farms. Capturing and using (and re-using) water using constructed elements such as tanks, swales, ponds and dams, and natural elements such as plant biomass and the soil itself, is the basis for ensuring water quantity and quality.

What about Urban Streams?

The impacts of human development in urban areas are similar but more extreme. While they may not be as visible (or perhaps not as noticed), urban streams have suffered even more than rural streams. The density of human settlement, the imperviousness of constructed surfaces such as roofs and roads, and the construction of drainage systems and infrastructure has meant that water in urban areas is more polluted and reaches the streams with more concentrated erosive force. The ultimate example of engineered response to stream degradation is the concrete channel, where the ecological role of a stream is completely subsumed by its role as an open pipe.

Urban Stream Syndrome

The degradation of urban streams now has a name. Urban Stream Syndrome refers to the suite of physical, chemical and biological changes which occur as a result of urbanization within stream catchments.

And it’s all bad. Physically, the increased rate at which run-off water reaches the stream increases its erosive force, so that stream beds and banks are eroded more and pool/riffle sequences are destroyed, and flash flooding is increased.

Chemically, the water in the stream comes to have higher levels of nutrients (from soils and home garden) and pollutants (from industry, roads and home gardens), and lower levels of oxygen. Recent work by Dr Ian Wright at University of Western Sydney suggests that the concrete pipes which take the runoff water may themselves be a hazard, as the dissolution of the concrete by the water changes the pH and levels of calcium and carbonate ions in the water as it passes through the pipes.

Biologically, the suite of fish and invertebrate species changes, with species less tolerant of the changes disappearing. Changes to riparian plant communities occur (if they haven’t already been removed) through bank erosion, changes in nutrient levels and the recruitment of weed species from the urban areas.

What’s Being Done?

Councils around Australia have since the 1980s been incorporating water retention in designs for public spaces. You may have noticed detention basins being incorporated in sports fields and green space. Since around 2000 councils have also started to incorporate Water Sensitive Urban Design (WSUD) concepts into public space and development designs and approvals.

WSUD is all about treating stormwater within the urban landscape by slowing and/or filtering it before it reaches a waterway, and reducing the amount of water which runs-off to waterways. Some common treatments you may have seen are gross pollutant traps, constructed wetlands, roof gardens and porous pavements in public areas.

Many councils are also beginning to do urban stream re-naturalisation work. This involves reinstating some of the features of a natural stream and could include removing concreted channels, reinstating the pool/riffle sequences using rocks or ‘large woody debris’ (i.e. logs), removing weeds and replanting with the mix of plant species which would have naturally occurred there.

What Can You Do?

An interesting idea emerged a few years ago from some WSUD planning work done by the Sydney Catchment Management Authority (now Greater Sydney Local Land Services). Their research with councils suggested that around 2% of all houses in Sydney were renovated or re-built in any one year. They also found that the biggest water quality improvements and reductions in demand for water could be achieved with water management at the household scale.

Taking a ‘glass half full’ view, they concluded that if councils continued to demand design public space and infrastructure with WSUD in mind and all renovations were required to have WSUD design features incorporated, then it would only take 50 years for the whole of Sydney to be ‘water sensitive’. They also did some scenario planning which showed that this level of WSUD adoption would result in downstream water quality being similar to 1788 conditions. Given the scale of the city and the task, 50 years seems to me like an eminently do-able time-frame.

Luckily, the barriers to adoption of sustainable urban water management are primarily social and institutional rather than technical. On your own suburban block you can do some things which are commonly “exempt development” such as swales, permeable driveways and paving, rainwater fed Permaculture/food gardens, rain-garden planter boxes, leaky water tanks and re-directed downpipes. Instructions and designs for these things can be readily found on the internet.

Raingardens are becoming quite common. They look just like normal gardens but are designed to take and use stormwater runoff from hard surfaces like your roof or driveway. They generally contain layers of sand and/or gravel which captures and slows the water and filters it. This keeps pollutants out of your local streams, reduces the erosive force of rainfall on those streams, and provides the water your garden needs.

It’s Not Just Personal

While it could be fun and beneficial to make your own home water-sensitive, such localised and small-scale solutions are also a critical part of achieving a water sensitive city and for resilience in general. Like much of the “blessed unrest” around the world which constitutes a bottom-up movement for social and environmental change, home gardeners can be political leaders.
Political leadership in this context involves marshalling interest and concern within the local community for improved water management. Local initiatives tackling environmental issues whereby community members just get on with what works and tell their stories, can be important in bringing issues to the attention of politicians and providing support for politicians who are keen to advance the issue.

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