Gravel moving into the Bay – report by John Butt

August 31, 2008

Local resident John Butt has devoted much energy into researching the alarming accumulation of gravel along the Eastbourne beaches. The Days Bay Residents Association consider this gravel is threatening the local beach in our Bay to the detriment of visitors’ & residents’ enjoyment. This situation is high on our agenda for serious discussion with the Council. Watch this Blog for further devlopments.

These photos are significant – John has taken a current photo from the same location at the south end of Muritai & shows the accumulated gravel all too clearly!

Could this happen in Days Bay – see more visual examples of John’s research at

Recent research by a local into the movement of the gravel “pulse” initiated by the 1855 earthquake debris from a major slip in the Orongorongo valley was discussed. The acres of gravel built up in Muritai Bay and Robinsons Bay continues to move, recent erosion of the beach at the south end of the Rec is now visible. The front edge of this gravel pulse was recorded in 1978 at Hinds Point, and in 1985 in Muritai Bay and is clearly still moving. The pulse was recorded moving around the coast in these two scientific papers, and new research has shown the pulse has arrived in Days Bay. It is made up of many thousands of cubic meters of gravel, moving with southerly storm waves along the beach and around each point. The leading edge was recorded moving inside the harbour at 400 meters per year in 1978 and 600 meters per year in the 1985 report by Carter & Gibb.
John Butt has found photos of Eastbourne bays at the Turnbull Library and repeated these photos from almost identical places to show the changes, these are on his website. The bulk of the pulse is now on each south facing coastal strip from Lions Rock to Eastbourne wharf. The 1978 report by E R Matthews was based on an experiment where 20 tonnes of fist sized pieces of brick tiles were placed at the beach by Lake Kohangapiripiri in 1978. These “tracers” are now easy to find in Rona Bay and Days Bay. The front edge of the pulse has arrived in The Bay, explaining the build up of gravel starting at the south end.
Relevant reports:
Coastal Sediment Dynamics, Turakirae head to Eastbourne, E R Matthews 1979
Days Bay – Beach Stabilisation Lionel Carter and Jeremy Gibb 1985

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