Blog 06 November 2012

 
News Updates today in St Francis Bay

1. ST FRANCIS CONNECT ARTICLE - Nevil Hulett Beach and Spit Opinion
Nevil Hulett Beach and Spit Opinion

Nevil Hulett Beach and Spit Opinion

I personally have the following viewpoints on the “Spit” and the whole of the St Francis Beach which are inseparably linked.

• Trying to maintain the current surf line along the spit using rock revetments :

  • Will entail the expenditure of millions immediately and 10 times more in the coming years due to the need for on-going maintenance due to storm damage.
  • Will result in the beach in front of the revetments retreating so that it is eventually no longer usable for recreation (i.e. too narrow at low tide and a danger at high tide).
  • • The spit (Sand Dunes and port Jackson) is not required for the healthy functioning of the canal system. What is required for the healthy functioning of the canal system is a 30 meter wide channel along the length of the “ski basin” to the Kromme river mouth.
    • I personally favour beach nourishment by pumping sand from the estuary and kept in in place by preferably “soft” groynes using sand bags. However “hard” groynes are tried and tested world wide and should not be ruled out.

    • A groyne on the south side of the river mouth would have the following immediate benefits:

  • Stabilizing of the river mouth channel making navigation out to sea safer for the public.
  • Eliminating the sand deposited during incoming tides into the “Ski basin” channel where it meets the river. In the early 90”s this caused the ski basin channel to be closed off completely causing serious problems with water quality due to insufficient circulation in the marina.
  • A build-up of sand on the south side of the groyne.
  • There are two factors that stand in the way of the implementation of the above:
    • Time : Apart from the time it takes to design and implement the above solutions there is the need for time consuming Environmental Impact Assessments with associated public participation.
    • Money: Suffice to say raising the required funds for the preferred solutions may not be easy and or immediate.

    To Buy the canal system time I propose a “managed retreat” for the following reasons:
    • There could be a delay due to EIA and design and implementation of the preferred solutions of between 2 months (dredging) and 52 months (hard groynes).
    • In this time there could be a breach of the “spit” putting the required 30 meter wide circulation channel along the “ski basin” being narrowed or closed.
    • My proposed managed retreat involves spending the minimum amount of money to maintain the 30 meter wide circulation channel along the “ski basin” in this interim period.

    Obviously a best case scenario would be that the spit does not breach during the above “delay time” and no money needs to be spent to keep the 30 meter wide circulation channel along the “ski basin” open.

    In a “worst case scenario” I propose the following “emergency” measures be undertaken.
    • A surveyed line is marked in the “ski basin” using poles at 50 meter intervals (marked with reflective tape so they are visible for boating traffic). This surveyed line must represent the eastern (sea side) edge of the 30 meter wide circulation channel along the “ski basin”.

    • Should the “spit” breach then nothing should be done (apart from “maintenance” dredging into the breach) until the erosion delta from the breach crosses this line. Once it does then a low (1.5 meter high by 3 meters wide) rock revetment should be placed on filter cloth on the erosion delta 10 meters on the sea side of the surveyed line. This has the following advantages:

  • The minimum is spent only on the area that is required to keep the 30 meter wide circulation channel along the “ski basin” open.
  • The money spent will be as far as possible from the dynamic surf zone minimising maintenance.
  • The rock from the low (1.5 meter high by 3 meters wide) temporary rock revetment can be reused once a “permanent” solution is implemented.
  • Should the rock not be required natural windblown sand will quickly cover the temporary rock revetment and can be vegetated with indigenous dune vegetation.
  • Sand from the breach erosion delta that crosses the surveyed line can be quickly and cost effectively dredged the short distance over the low (1.5 meter high by 3 meters wide) temporary rock revetment using the Riparian associations dredger thereby restoring the 30 meter wide circulation channel.
  • Lastly and most importantly:
    • Duncan Lethbridge Jnr has the Rock stockpile, the 4 wheel drive tractor and trailer and the excavator necessary for this emergency measure available immediately.
    • An extension of the current approved EIA should be easily obtained to enable this emergency measure to be implemented at short notice.
    • There is a good chance that the “spit” will not breach until the end of the year thereby eliminating the need for an access road on top of the spit as the 4 wheel drive tractor and trailer and the excavator can move along the hard sand at low tide without the threat of legal action by the PEM guys (Their contract would of expired).

    Lastly a precaution against a 1 in a 100 year storm event (That would require faster implementation than possible by Duncan Lethbridge Jnr) it would be prudent to create a large stock pile of suitable rock locally and to ascertain the availability and cost of
    additional all terrain dump trucks (CAT 6 wheel drive dump trucks are ideal).
    • Best case scenario is that this rock is not required to be utilized for the low (1.5 meter high by 3 meters wide) temporary rock revetment can be reused once a “permanent” solution is implemented.

    Please feel free to email or call me if you would like to discuss any of the above proposals in depth.
    Regards Nevil Hulett
    Cell 082-552-9231
    Fax 086-689-1304
    nevilhulett@gmail.com



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