Pinehaven has a long history of regular flooding events, with 1976 being the largest; Whitemans Road bore the brunt of the floodwaters.
The following year, GWRC and UHCC agreed to jointly administer the Pinehaven Stream with the Watercourses Agreement. However, it became apparent that the flooding issues were closely integrated with the piped stormwater reticulation system. The catchment is also quite contained in nature, within a built environment.
GWRC expressed a desire to transfer responsibility for the Pinehaven Stream to UHCC. The trouble was that the District Plan objectives, policies and rules did not recognise the identified Flood Hazard Extent and associated risk to development for either the Mangaroa River or the Pinehaven Stream. Quite clearly, there was a need to sort out structures that were impeding the flow of water during heavy rain events and improve the capacity of the Pinehaven Stream.
In 2012, GWRC and UHCC worked towards this with Plan Change 15 – Mangaroa River Flood Hazard Assessment. But, there was some discomfort with the flooding modelling results and Plan Change 15 expired over an extended review period. Next, with the Pinehaven Floodplain Management Plan (PFMP) in hand, both councils committed to Plan Change 42 and splitting the Pinehaven Stream Structural Improvements project cost 50/50.
On 27 March 2018, the Upper Hutt City Council (UHCC) unanimously approved Plan Change 42 (PC42). This moment was the culmination of decades of work by Greater Wellington Regional Council (GWRC) and UHCC to address the vexing issue of flood management for Pinehaven community. Two appeals were then lodged with the Environment Court; one relating to matters not affecting the project and the second by Save Our Hills – appealing the entirety of PC42. Experts’ conferencing was completed on 8 April and 9 April 2019. At the May mediation session, Save Our Hills advised that they had withdrawn their appeal. Other parties who joined the appeal continue to work with GWRC.
There will be less vegetative debris in the stream after the project
Plan Change 42 – Mangaroa & Pinehaven Flood Hazard Extents
Plan Change 42:
Addresses-the risk from flooding within the Mangaroa and Pinehaven stream catchments for the 1:100 year flood event. The proposed provisions seek to avoid development in the high hazard area and avoid and mitigate the risk of flooding in the lower hazard areas. A range of structural and non-structural measures are to be put in place, to reduce flood risk to the community.
Complements- the physical stream improvements works by seeking to reduce stormwater generation and the exposure of third parties to flood risk. It also includes some elements that enable the stream improvement works to be carried out.
Introduces- new objectives, policies, rules and other methods to address flooding risks associated with the Pinehaven Stream and Mangaroa River catchments. These new tools provide for certain developments and activities to be avoided with specified (high-risk) areas, and require mitigation and avoidance within other (lower risk) specified areas.