So far, engineers and consultants have only considered "Mother Nature" and the Regional Council Coastal Strategy is focused on "climate change". Clifton to Haumoana is simple engineering but beaches and property between Clive and Tangoio are in big trouble if Councils continue to ignore the real causes. Just like Westshore, installing a solution without knowing the cause is reckless engineering.
Sooner rather than later, Councils need to consider man-made impediments to the movement of coastal sediment between the source of greywacke stone in the Ruahine and Kaweka Ranges and the beaches dependant on vital replenishment. Over the last 80 odd years, development has changed the landscape but the price has been unforeseen consequences on the coast. Protection for property and infrastructure on and behind the shingle spits has been severely compromised.
Someone could look at the good work of the old Catchment Board and the more recent river and coastline management by the Regional Council and consider the influence of river diversions, stop banks and river gradients slowing gravel movement. Also consider the vast quantities of shingle extracted by numerous screening and crushing plants along the three rivers and the one still on the coast.
Engineers could consider the protruding impediments such as protection for sewer outlets, the Port breakwater, the Perfume Point mole and the remains of the western pier built for the old British Freezing Works. Eventually they will have to consider the regularly deepened shipping channel which traps all seabed sand flowing in the northerly coastal sediment drift. This material is the sole source of stable replenishment for beaches between Hardinge Rd and Tangoio.
Unfortunately, engineers accepted the $111,400 Komar report which overlooked the significance of the deep trench for harbour navigation. This cornerstone report incorrectly concluded gravel never passed Bluff Hill, before or after construction of the Port breakwater.
Port dredging records clearly show 25,000m3 to 30,000m3 of sand accumulates in the shipping channel each year. Council engineers will not accept Prof Komar now agrees this blocked material would otherwise replenish Westshore Beach and then feed Bayview and Whirinaki.
The Port insists they have been exonerated but concede the breakwater contributes about 5 per cent to beach erosion. Their owner, the Regional Council, stated in the Consent for the Whakarire Ave Revetment Project (October 2016) that "Port development caused natural inputs of sediments to southern Westshore Beach to cease". I agree with Prof Komar, the breakwater sheltered Westshore and transformed a mainly gravel beach into a popular sandy beach that maintained a constant state of accretion until the 1980s.
Consequences City Leaders continue to ignore include:
1. Hawkes Bay residents, visitors and tourists have lost a once popular swimming sandy beach because they carried on with a totally inadequate solution.
2. The inshore sediment deficit within 300m of the low tide mark has been accurately measured at 406,000m3 using marine survey data. This serious accelerating net loss of nearshore sand accounts for the steeper gradient, narrower usable beach and loss of safe surf conditions.
3. The new Coastal Erosion Zone now includes 504 Westshore and Bayview homes valued at $263 million. LIM reports tagged to property titles will limit insurance cover, mortgage finance will be difficult and land values will be adjusted to nil value in 100 years. (includes houses that lose road access)
4. The loss of shoreline reserve and city infrastructure will bring total losses close to $400 million. The less than $15 million solution would be a good investment for the Port Company.
Being made to wait almost six years so far, to have the CEO validate my assessment, could be rewarded one day if Hawkes Bay Today includes a Napier beach in the "Top nine beaches to visit in Hawkes Bay".
- Larry Dallimore is a Napier City councillor and long-time campaigner for Westshore beach.
