A good kick in the groyne
Similar to to the 2022 election we have had a renewed call for the construction of groynes at Ocean Beach Domain in time for the election in 2025. Very little has occurred coastally in the intervening years. Perhaps the other concern is the lack of action on wider coastal plans for areas such as Brighton, Waldronville, Tomahawk and Waikouaiti. All of these areas have issues over their management as coastal buffers to low-lying communities. Ocean Beach Domain has dominated the coastal narrative for at least the last 3 decades, often at the expense of other areas.
While a lot has been written about protecting South Dunedin from flooding, there has been no broader view given to protecting the area from coastal innundation. Its well documented that their has been periods of significant dune collapse and extensive flooding as far as Hillside Road. Both catchment management and storm defenses must be a dual consideration for the area, particularly if wetland redevelopment occurs as part of the South Dunedin strategy. Sand dunes are like saving money for a rainy day. You build up sand in preparation for storms and provide the conditions for building up sand again after them. Its cyclical and accepts that nature will take its course, but with proactive management will return to be an effective buffer again.
For all of the talk about expensive engineering solutions, there has been no discussion about taking an ecological and land use approach to dune strengthening of Ocean Beach Domain or other areas for that matter. An ecological approach means instead of expensive engineering you change how the land is used and strengthen fore, mid and rear dunes with planting and appropriate acceas development. It requires flexibility and an approach based on the conditions at the time and in the future. Its proactive not reactive.
So, in a nutshell the following are the best options for Ocean Beach Domain going forward:
- Change the land use of the area back to a natural dune system.
- Investing in long-term constant revegetation for sand trapping.
- Providing access in properly designed key areas.
- Allow for loss by proactive management, including renourishment, dune shaping and revegetation.
So, why will groynes not work at St Clair? The answer is twofold, the renewal and lengthening of the wall that was extended seawards in the early 2000s has lowered the beach so much that there is no space or potential for enough sand movement. They worked in the 19th century because the beach was not dealing with the erosional effects of the present sea wall that has made the beach narrower and lower. The current St Clair sea wall is a major problem for exacerbating the continued erosional cycle we see today and cannot be solved with groynes.
Could the wall be fixed?
It could be by moving it back to its original 1913 position, but there is no guarantee. It would work and it would be hideously expensive. Probably the cheapest option is to maintain it’s current position, but proactively manage the associated erosion with sand sausages and renourishment. Not ideal, but financially and strategically the easiest option.
As a City Councillor I have the skills and overview of our coastal areas to protect our communities in the longer term. We don’t need expensive over-engineered solutions produced by external consultants. We need locally produced plans of revitalisation using proven ecological and land management techniques.
If you’d like to know more click on the link to my coastal page and read my 2008 overview for Ocean Beach Domain ignored by the Dunedin City Council at the time. Or follow my Facebook Page “The beginners guide to coastal conservation.”
