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Waste, recycling and reuse

This section reports on the following environmental indicators, which are defined in Newton et al. (1998).

This section of the report documents the waste of our current industrial and settlement systems in relation to stormwater and wastewater, and solid, liquid and hazardous wastes. It also examines briefly the implications of continuing a business-as-usual approach to the use of transport and energy in our cities from the perspective of urban air quality and greenhouse gas emissions. In all arenas, it is possible to identify opportunities for converting what are still considered by many in industry, government and community to be 'waste streams' into productive assets, via recycling, reuse, industrial ecology, eco-efficiency, cleaner production, and material reactivation technologies and processes. Such new activities and industries are in their infancy and constitute the beginning of what some have termed 'the next industrial revolution' (Hawken et al. 1999).

Urban stormwater

Providing stormwater services

The objectives of stormwater management have broadened over the last decade, from purely flood protection, to encompass pollution control, ecological regeneration and enhancement of stormwater amenity value (Thomas et al. 1997). Water can provide other values in our urban landscape apart from a supply source. Water bodies such as ponds and wetlands as well as creeks, streams and rivers can add significantly to the aesthetic and recreational amenity of an urban area. A growing appreciation for the importance of water in the urban environment and concern about the impact of past practices has supported the adoption of the concept of water-sensitive urban design within the stormwater industry in Australia.

In the Melbourne metropolitan area, for example, the stormwater system comprises approximately 25 000 km of street drains, 1100 km of main drains and drainage channels, and 5000 km of waterways (Collett 1994). Stormwater is discharged into the environment at more than 1000 locations across Melbourne, of which nearly 400 discharge directly into Port Phillip Bay.

Table 58 outlines the institutional arrangements for provision of stormwater services in the states and territories of Australia. Thomas et al. (1997) concluded that, throughout Australia, arrangements for integrating stormwater management (both flood control and drainage) are generally chaotic. Control is generally very fragmented and there is a lack of clear accountability for various parts of the water cycle. Furthermore, the relationship between the various operators, regulators and councils is often blurred, and in many cases the operating agencies are also involved in standard or target setting.

Source:Thomas et al. (1997).

Stormwater discharges to the environment

The average volume of stormwater discharged nationally is about 3000 GL per year (Anderson 1995). Compared to water supply and wastewater flows, comparatively little is known about the volumes and quality of stormwater flows from towns and metropolitan areas into estuarine and coastal waters.

The generation of significant quantities of runoff from expanding urban areas is recognised to be a major management issue faced by administering state and local governments (WBM Oceanics Australia 1999). For example, a comparison of two adjoining catchments on the fringe of Canberra found that the average annual runoff from the urban catchment was more than five times greater than the rural catchment, despite the rural catchment receiving only 5% less rainfall annually (Laurenson et al. 1985). Increasing volumes, the temporal variability of flow, limitations on storage and contamination all influence stormwater management decisions (WBM Oceanics Australia 1999).

The quantity of stormwater shed by an urban area is a function of climate, geology, topography, degree of imperviousness and stormwater drainage practices. Urban areas usually cover part of one or more catchments and, in the case of Australia's many coastal settlements, the urban area is located at the lowest reaches of these catchments. The quantity of stormwater flowing from the catchment is only in part generated from the urbanised portion of that catchment. This makes it difficult to separate the quality of stormwater that is generated from the urban area and discharged to receiving waters from that of the non-urbanised portion of the catchment, using data recorded at downstream flow gauging stations.

Urban consolidation can have a considerable impact on stormwater volume and velocity because of the increased area of impervious surfaces. While greater urban density leads to smaller blocks that require less garden watering, it will contribute to greater stormwater problems without sufficient management (Dowsett 1994).

Average annual stormwater discharged from Adelaide has been estimated to range from 150 to 185 GL (Fisher and Clark 1989; Environmental Consulting Australia et al. 1991), which includes runoff from upstream rural areas and outflow from the Mt Lofty water supply reservoir. All other urban settlements in South Australia (defined as those serviced by reticulated sewerage) are estimated to generate 9 GL/year of stormwater on average (McIntosh and Pugh 1991). Argent (1995) estimated that Melbourne generates 470 GL/year of stormwater, while Sydney generates 420 GL/year, based on rainfall, total urban area and an average annual volumetric runoff coefficient. WBM Oceanics Australia (1999) estimated that 54.4 GL/year of stormwater is shed from the 20% impervious fraction in the 320 km² of metropolitan Perth. Because of the sandy soil which underlies most of Perth, much of this stormwater is disposed of locally using spoon drains and stormwater infiltration basins. In Canberra, the 27km² Curtin catchment is 60% built-up, has an impervious fraction of 26%, and an average annual rainfall of 630 mm. One-third of this rainfall becomes stormwater, equal to some 5.5 GL/y (Mitchell 1998).

Table 59 presents stormwater volumes from a selection of small catchments in capital cities of eastern states. The size, rainfall, percentage impervious area and resultant annual average stormwater volume varies. Greendale Creek in Sydney has the highest percentage of effective impervious area and generates the greatest amount of stormwater, despite being the second smallest catchment.

Source: Chiew and McMahon (1999).

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