How can Southshore live with the sea?

From Christchurch Dilemmas, 6:00 am on 7 August 2017

The 1200 residents of Christchurch's Southshore enjoy enviable access to both the estuary and the Pacific Ocean. But for how much longer?

As coastal communities throughout the country grapple with complex sea-level rise scenarios, the people of Southshore are seeking their own solution.

Disappointed with both the government and council’s response to a request to repair collapsed walls along the red-zoned estuary edge, the Southshore Residents’ Association has put forward its own plan for an engineered berm.

Association chair Bill Simpson says the community has weathered the “perfect storm” three times in the last two years.

“What that means is you get high tide, high rainfall and a pretty mean wind coming from the other side of the estuary, and that forces water against the water edge here, and the water is driven up into the houses.”

Residents who rebuilt post-quake now live in higher homes, and many who were one or two houses back from the estuary now have sea views.

Across the estuary is the recently-completed Beachville sea wall at Redcliffs. “Theirs is a hard rock solution, the solution for Southshore might be a lot different,” says Simpson.

In fact, the solution supported by 98 percent of Southshore residents is a planted berm, with space for a walkway on the top.

Deidre Hart, a senior lecturer in coastal studies at the University of Canterbury, says there is "more than just the physical elements to look at here, there's pros and cons for a community and the values that they have for this area”.

The post-quake estuary environment is dynamic and ever-changing, in the same way the Napier coastline is still adapting to the effects of the 1931 earthquake.

As for sea-level rise, Hart says there’s been a 21cm increase over the last century. A 20-40cm rise is predicted over the next 50 years.

“After that it is not so much that there's disagreement, but there are different scenarios based on what we do as humans in terms of our interaction with the atmosphere. So there's potential to change our future.”

Southshore resident Vivienne Johnson says the earthquake has “increased our awareness of our vulnerability” and she worries “for the new people coming and investing in new properties for their future”.