The Nelson Tasman region is experiencing unprecedented growth with the development of greenfield areas. Stream channels within these areas are being modified on an ad hoc basis without considering ecological, fluvial-geomorphological or engineering principles, design, and processes.
In the absence of national or regional-specific guidance material, the current ad hoc approach results in mixed and often undesirable outcomes. Stream channels are over-armoured with large rocks, or erosion is being exacerbated by poor channel design. These changes lead to the cumulative loss of habitat heterogeneity for aquatic biota, altered stream behaviour, increased sediment loading, and risk to infrastructure from erosion with improved future management and maintenance costs.
The scientific and engineering communities have understood stream dynamics and function principles internationally and within New Zealand for some time. International literature and stream design and management case studies have also become available in recent years. However, comprehensive stream design guidelines in New Zealand need to be more effectively present.
Tasman District Council (TDC) acknowledged the need for authorities to provide greenfield developers and resource consent applicants with a practical framework to design stream channels appropriately.
Stream Design Guidelines were developed based on ecological, fluvial-geomorphological, engineering principles and best practices.
The guideline contains local stream type definitions, an overview of ‘type specific’ stream channel processes and potential risks to diversions, technical design elements and conceptual design schematic figures. The guideline provides a step-by-step process of designing a stream channel, from preliminary assessments and design to resource consent application, detailed design and construction.
The Stream Design Guideline will inform and aid land development project teams to best retain, design and manage streams through their developments. It is envisaged that the Stream Design Guideline will also help developers, practitioners, resource consent applicants and TDC to meet the statutory requirements of the Resource Management Act (RMA), the Tasman Regional Policy Statement and the Tasman Resource Management Plan. The Stream Design Guideline incorporates cross-discipline principles to meet local and national objectives, leaving streams in a better state for the next generation.
