Coastal erosion workshop

We had an interesting session this afternoon with coastal researchers, Jim Dahm and Bronwen Gibberd, who are working for Porirua City Council to get information about coastal hazards and erosion, and starting to prepare long-term plans to prevent them getting worse.

We had a small turnout (about 10 locals), but they were mostly people who had lived at the beach for many years and could tell the researchers a lot about the beach and how it has changed over the decades.

There were some interesting insights, such as:

  1. There are really three separate areas along the beach, each with differing characteristics:
    1. Brendan beach, where the problem is mostly sand building up after storms (accretion)
    2. the ‘middle’ beach, which is pretty stable and doesn’t suffer from much erosion
    3. the beach at the western end, near the boat ramp, where most of the erosion occurs
  2.  Most of the time the beach is stable — it is only storms that cause major problems (i.e. the beach is generally protected from regular currents bringing material onto the beach)
  3. A lot of sand seems to drift down the coast from the north and ends up on Brendan beach in storms or deposited on the sea bed in the Bay
  4. A half-metre rise in sea level can push the beach back inland by 30–50 metres
  5. Hard barriers, such as sea walls, are no longer favoured for protection because, while they protect what’s behind them, they cause problems with the beach in front.

Jim and Bronwen are very interested in finding out as much as they can about how the beach has changed in the past 30–40 years, and would like to hear from people who have information about that. They are particularly interested in getting photos of the beach — it doesn’t matter if they are family snapshots or home movies, as long as they show parts of the beach.

If you have any information that might be useful for them to get a clearer picture of how Pukerua Bay beach has changed, you can contact them through coastal.hazards@poriruacity.govt.nz.

Pukerua Bay beach in 1957

Today’s workshop was the first of several. They will be back in about the middle of September to talk about the things the council will have to look at over the long-term (50–100 years) to mitigate the effects of storms, erosion and sea level rise. Keep an eye out for the publicity.

More information here on PCC’s website

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