October 24, 2023

Portlink Setbacks


Where does a riverbank start? Sounds like a simplistic question but for planners and developers, as well as for the rest of us, it’s really important that we all agree on the answer to that apparently simple question.

The Ōpāwaho Heathcote River is what planners call a Downstream Waterway, a term that they apply to the downstream sections of large rivers with wide beds, continuous flow, extensive floodplains and, in many cases, tidal reaches.

The Christchurch District Plan wisely states that the margins of such downstream rivers should not be developed, so that, amongst other things, these river margins can used for maintaining or enhancing habitat for animals and plants, and contribute to the open space character and amenity values of the surrounding area.

To that end, the District Plan quite clearly lays down that there must be a 30m setback from the river for any development. Within this setback, no-one is allowed to do earthworks, construct buildings and other structures including laying down impervious surfaces like asphalt. How sensible! Imagine if the original settlers had had such a plan – and had stuck to it!

Now, where is this 30m setback to be measured from? Quite plainly, the District Plan states that the 30m setback will be measured from the river bank and just in case anyone wants to debate where the river bank starts, the District Plan in “Appendix Interpretation of banks of water bodies” provides a helpful diagram which is included here.


A screenshot of the Christchurch District Plan’s explanation of where a 30m setback should be measured from. Click to see the full version.

Unfortunately, as you can see, the diagram mentions two slightly different descriptions of the point at which the river touches the land denoting the beginning of the riverbank: “normal low flow water level” and “normal average flow water level”. Are these the same thing? What does “low flow” mean? Is it “low” as in “not high” flow – the normal amount of water when the river is not in flood? Or is it “low” as in the “lowest” flow – the normal flow when there has not been a rain event for a long time? Or something else?

Pause that thinking for a moment and consider the fact that twice every day the tide washes in and out and in doing so raises and lowers the level of the river in its lowest reaches quite substantially although the tidal effect can be detected as far up the river as Buxton Terrace. How do we think about the “normal low flow water level” and “normal average flow water level” for these tidal reaches of the river? The river keeps flowing at the same pace during high tide as it does at low tide after all.

Enter the Portlink Industrial Park developer with a tame planner in tow. They are looking for a way to minimise the fact that they have deliberately intruded into the 30m setback with hardstanding, a fence and a container park. What interpretation do they make of where to measure the 30m setback from? To the developer’s planner, it is obvious; the wording in the District Plan means that, while almost holding a straight face, they can claim that the river bank starts at the point at which the river meets land when the tide is at its lowest, even though this point, far out in the middle of the mudflat, may be underwater for all but about two hours each day! For them, the river bank is near the middle of the river!

The CCC consent team prefer an interpretation of “bank” which seems a little more reasonable given the wording in the District Plan. They believe the river bank starts at the point which is at the average of high and low tide, thus keeping faith with the “normal average flow water level” wording. Who is correct? Only a Hearings Commissioner can decide, but it would have been a lot easier if the wording had been more precise to begin with and took into account the effects of tide.


Note the end of the river as a straight line demarking the beginning of the coastal marine area (light blue) a little way upstream of the Ferry Road bridge.

OHRN takes a still different view. We look to the coastal marine area for the answer. Rivers eventually have to meet the coast and you would think it would be a good idea if the point at which the river bank commences was identical for both beside the river and also where that river joins the coast. Both the Resource Management Act and the Foreshore & Seabed Acts use the Mean High Water Spring (MHWS) level as the dividing line between land and water. The landward boundary where the coastal marine area meets a river is “at that point…whichever is the lesser of (i) 1 kilometre upstream from the mouth of the river; or (ii) the point upstream that is calculated by multiplying the width of the river mouth by 5.”

It might come as a surprise to many that the designation of a Downstream Waterway stops short of the actual sea. For the Ōpāwaho Heathcote River, the coastal marine area cuts across the river as a line between the southern corner of what used to be Maritime Place and the north-west corner of a reserve in Bridle Path Road. Have a look at the planning map.

To OHRN, the Mean High Water Spring (MHWS) level would be the best demarcation point for the riverbank of a river where it is influenced by tidal flows. It would make it quite clear where the riverbank started, and it would not be out in the middle of a mudflat!

SetbacksThe issue will be determined by the Hearing Commissioner when the Portlink Industrial Park resource consent is finally heard. We look forward to that time.

This one of a number of articles about the Portlink Industrial Park.  Click to read previous articles on this topic.