Riparian corridors to be determined by Strahler stream ordering methodology

In brief - Strahler system to replace Riparian Corridor Objective Setting (RCOS)

The NSW Department of Planning and Infrastructure has announced that from 1 July 2012, the former RCOS approach to riparian corridors is to be replaced by the more objective Strahler stream ordering methodology.

Traditional disagreement on riparian corridors between developers and consent authorities

Disputes over the extent of riparian corridors and the permissible uses within these corridors continue to bedevil greenfield development projects.

Part of the tension lay in the often arbitrary nature of what consent authorities have considered to be environmentally appropriate to protect the integrity of the watercourse on the one hand, and the often substantial loss of developable land - and the associated impact on profitability – resulting from the imposition of riparian corridors on the other hand.

"Stream order hierarchy" approach for determining riparian corridors

In a bid to alleviate some of the problems associated with these tensions, and in recognition of the often inappropriate scale of corridors imposed on greenfield development projects, the NSW Department of Planning and Infrastructure has announced a new approach or methodology for determining riparian corridors.

In summary, the former Riparian Corridor Objective Setting (RCOS) approach is to be replaced by the so-called Strahler stream ordering methodology. This methodology, which is essentially a "stream order hierarchy", was officially proposed in the early 1950s by Arthur Newell Strahler, a geoscience professor at Columbia University in New York City.

According to the Department, the methodology provides a more objective approach which includes set riparian corridor widths, as opposed to the more discretionary RCOS regime.

Advantages of Strahler approach to riparian corridors

According the Department, the adoption of the new methodology and the related reforms are anticipated to:

• establish clear and appropriate rules on the width of riparian corridors
• provide greater flexibility in urban design by allowing a broader range of uses in riparian corridors, including detention basins, cycleways, roads and recreational areas
• enable works and activities to be offset along the length of a riparian corridor
• provide greater flexibility with watercourse crossing design
• remove the need for vegetated buffers in addition to a riparian zone
• introduce a streamlined assessment approach so that compliant proposals can be assessed more quickly

NSW Office of Water to manage new methodology

The new methodology will be managed and implemented by the NSW Office of Water, to which local councils and developers will need to refer. It is also anticipated that much of the work associated with determining the scale and extent of riparian corridors will be addressed as part of the rezoning process.

The Department of Planning and Infrastructure has announced that the reforms will apply across the state from 1 July 2012.