Barbados Wetland Hydro-Ecological Design

The Barbados Wetland is located in the mid upper reaches of the Alexandra Stream, which discharges into the lower Oteha Valley Stream, on Auckland North Shore. In 2004 as part of the Streamwalk Ecological and Engineering Stream Survey, for the Northshore City Council Network Discharge Consent application, Barbados Wetland was identified as a site for erosion remediation works and ecological enhancement.

There has been a recent trend in New Zealand to use ecologically based design principles in the management of erosion in urban streams and to improve hydrologic function to wetland systems. This involves the use of bioengineering techniques, materials and natural system design such the inclusion of pools, riffles and point bars into the finished geometry.

This paper documents the biophysical process assessed in the Barbados Wetland and the ecological, morphological and hydraulic design components used to develop detailed design. This includes discussion of the design process, key elements and research outcomes that informed the final detailed design.

As the construction supervision was conducted by the designers, the learnings and construction practicalities are documented and discussed in this paper. This is of particular interest in terms of the design of a dynamic natural system, which requires informed decisions to be made, ‘on the fly’, during the construction phase, such as riffle and point bar placement.

The Barbados Wetland Enhancement project is award winning and is an excellent example of a multi-disciplinary approach to erosion remediation works and wetland enhancement.