The institutional arrangements for decision making on urban stormwater management in Australia are currently shared across three levels of government. This influences the way in which local government bodies cooperate or compete, and, in the case of Brownhill Creek, this had a significant impact on the resulting stormwater plan. At a lower level, dissent among community action groups that favored different options fed upwards into the democratic processes of local government. The state and commonwealth governments each avoided involvement, (aside from elected local members declaring support for the no dam option), and used local government as a filter to produce consensus decisions representative of the five councils as a whole. Heterogeneity of community support for options among councils, therefore, became a consideration in reaching a final decision.
2.1. Responsibilities and Interactions between Levels of Government
In Australia, three levels of government are involved in flood mitigation in urban areas. Local government councils have responsibility for zoning land to prevent construction on flood prone land and to provide and maintain urban stormwater drainage infrastructure. State governments have ownership of all water resources and are responsible for land planning policies to which councils should adhere. The Commonwealth (National) Government formerly played a role in informing state water policies, through the National Water Commission, but, with its abolition in 2015, its primary national roles are serving as the Bureau of Meteorology’s flood warning service and providing emergency funding to flood victims.
The South Australian (SA) Government formed catchment water management boards under the Catchment Water Management Act 1995 to produce catchment water management plans that addressed surface water and groundwater resources, flooding, riparian ecosystems, water quality protection and improvement and were funded by a levy on all land owners that was collected by local government councils on behalf of the boards. The Boards were to have community participation and to invest and help coordinate activities of councils where urban catchments involved multiple councils. The Brownhill Creek catchment fell within the responsibilities of the Patawolonga Catchment Water Management Board, which undertook a flood study that in 2006 produced a map of the urban area prone to flooding in the 100-year ARI flood and made recommendations on actions to prevent flooding and reduce damage.
The Catchment Water Management Boards (CWMBs) were seen to be effective in engaging communities in management of water and the environment, so, in 2004, the SA Government extended the concept by passing the Natural Resources Management Act which created eight regional Natural Resources Management Boards to cover SA. These were larger geographically and had a wider scope of functions including vegetation, wildlife, land and bushfire planning and subsumed the CWMBs. Brownhill Creek now fell under the responsibility of the Adelaide and Mount Lofty Ranges Natural Resources Management Board (AMLRNRMB). Levies were not increased so the amount of effort on water management declined significantly. Boards became known as places where water management plans were devised but under reduced funding were largely moribund unless executed by other parties, such as local government or through Commonwealth grants. State Government responded in part by establishing the Stormwater Management Authority (SMA) under the Local Government (Stormwater Management) Amendment Act 2007 with the support of the Local Government Association. By 2013, the two parties had signed a new nonbinding agreement over the role and scope of the Stormwater Management Authority, which appears to focus only on flood mitigation. It also commissioned a new study of flood management options for Brownhill and the adjacent Keswick Creek with costs to be shared by the five councils within the catchments of these streams.
The Brown Hill Keswick Creek Project Office was established and supported by councils and the SMA to develop a flood mitigation plan. The process of developing the plan has been carried out in accordance with the Stormwater Management Planning Guidelines of the SMA. These expect a level of community consultation which depends on factors such as the size of the catchment, the nature and complexity of stormwater management issues, the nature of the adopted management strategies and the impact of the strategies on the local community. The two formal community consultation processes (2011 and 2015) were carried out by consultants, hired by the Project Office, in accordance with relevant policies of the five project councils whose jurisdictions covered the catchment. The councils determined which options were to be considered and go to public consultation. Proposals for consultation were developed only to a concept level of detail. Subject to community support, the proposals would then form a stormwater management plan (SMP) for which approval would be sought from the Stormwater Management Authority (SMA). At the implementation stage of the approved SMP, further consultation would take place which would involve collaboration with directly affected stakeholders, including owners and residents of properties traversed by the watercourse in which works are proposed.
If councils failed to reach agreement on flood mitigation works, the SMA had the authority to direct works to be undertaken at the councils’ expense. It was also implied that if councils failed to reach agreement, the state government may be unwilling to contribute to works from its own budget.
2.2. Brownhill Creek Geography and Flood Risk
The Adelaide Metropolitan Area is on a coastal plain between the Mt Lofty Ranges and the Gulf of St Vincent. It is traversed by three rivers, each of which has a water supply dam upstream that assists in mitigating floods from the upper rural catchment. Each river also has a linear park along its course through the urban area to act as a major recreational amenity, support natural habitat and to serve as a flood drainage channel to mitigate flooding from the urban catchment. The city also has 25 creeks and drains in the urban area but only four are considered to have a high risk of major floods, Brownhill Creek, Cobbler Creek, Dry Creek and Pedlar Creek. Of these, Brownhill Creek presents the most significant risk, as there is no flood control dam in its upper catchment, and councils have allowed residential development over its flood plain, and even over the channel itself. As recently as 2015, several meters depth of fill has been spread on the flood plain close to the edge of the creek channel and houses built with floor levels above flood level, substantially reducing the flow capacity of the river floodplain. Brownhill Creek and its smaller neighboring Keswick Creek, which meet near Adelaide airport, are largely canalized and used as the main stormwater drains by these councils, severely compromising the ecological value of the creek downstream. Where the natural channel has been retained it has been scoured by increasing peak flows due to urbanization. The urban catchment area has been marked for urban consolidation under the metropolitan area development plan, but the rural catchment is part of the hills face zone and new development there is prohibited, reflecting the value placed on the natural bushland visible from much of the city. It was clear that a stormwater management plan was needed, and that all councils would need to take responsibility to prevent excessive flooding in the downstream council areas, shown for a composite map of 100-year average return interval floods (Figure 1
). Brownhill Creek flows from the south east through the Cities of Mitcham and Unley to the City of West Torrens in the west before discharging into the Gulf of St Vincent to the west of Figure 1
. Keswick Creek flows from City of Unley in the east and is joined by a northern tributary passing through the Cities of Burnside and Adelaide before connecting with Brownhill Creek just east of the airport in the City of West Torrens.