RiVAS - Natural Character in the Hawkes Bay

The purpose of this case study was to use the River Values Assessment System (RiVAS) model to assess natural character of rivers in the Hawke’s Bay region.

Natural character in this study was defined as “The naturalness of river environments".

The degree or level of natural character within an area depends on:

  1. The extent to which natural elements, patterns and processes occur; and
  2. The nature and extent of modifications to the ecosystems and landscape/riverscape.

The highest degree of natural character … occurs where there is least modification. The effect of different types of modification upon the natural character of an area varies with the context and may be perceived differently by different parts of the community.”

RiVAS was used to rank the natural character of Hawkes Bay waterways from high to low. This information was used by the panel from a workshop study to begin discussions surrounding possible future planning in an effort to enhance and restore waterways’ “naturalness” in the region.

Method

The River Values Assessment System method can be summarised in 14 steps;

  1. Define river value categories and river segments
  2. Identify attributes
  3. Select and describe the primary attributes
  4. Identify indicators
  5. Determine indicator thresholds
  6. Apply indicators and indicator thresholds
  7. Weight the primary attributes
  8. Determine river significance
  9. Outline other relevant factors
  10. Apply to potential river scenarios (Called RiVAS+)
  11. Apply to potential river scenarios (Called RiVAS+)
  12. Apply to potential river scenarios (Called RiVAS+)
  13. Apply to potential river scenarios (Called RiVAS+)
  14. Identify information requirements         

In this case study the introduction of RiVAS+, a future advancement to the RiVAS model which is still under development, was introduced in the latter steps of the framework as a means to enhance future natural character of waterways in the Hawke’s Bay region. RiVAS+ was used to assess the potential value of six segments of rivers for natural character, with a variety of types of rivers being chosen for testing (Urban, Coastal & Rural).

Outputs

RiVAS findings             

Hawkes Bay natural character rivers mapped by significance level

 

In addition to the RiVAS findings above on the current state of waterways with in the region,  RiVAS+ modelling indicated that there was reasonable potential to improve at least a portion of considered river sections, raising their current state from low significance to that of moderate significance. The management strategies for improving natural character most commonly identified included: increases in minimum flow, control of weeds, plant riparian native vegetation and creation of natural channels.

Recommendations

This case study report was based on a one day workshop, while it displayed both RiVAS’ ability to classify current river systems in terms of natural character and RiVAS+’ ability to model future changes to a section of river and how those changes could possibly effect natural character of the area, it was a potentially limited study in terms of time for wider community input and detailed assessment. There is scope for a more detailed use of the RiVAS models.  

               

Associated Models

River Values Assessment System (RiVAS)

The RiVAS tool (and its underlying method) uses a multi-criteria analysis (MCA) approach and aims to:

References

Kay Booth (2012) Natural Character in Hawke’s Bay: Application of the River Values Assessment System (RiVAS and RiVAS+). LEaP Research Paper No. 15. HBRC Plan: 4375