Development Application - Part 2 of 2 - Report & Plans · OPW11/0116

     3.2.   Option B - Establish Erosion Limit Control Lines

The present strategy of establishing erosion limit control lines has been partially implemented by Council and in areas where
these limits were deemed to have been breached, rock walls have been constructed to prevent further erosion beyond these
limits. Given the extent of recent erosion, it may be that erosion control lines have been breached in other locations,
triggering construction of additional rock walls under the present strategy.

Option B involves hardening of the bank and as such does not have an appreciable effect on flows. No additional numerical
modeling was completed for this option.

In the medium-term, it would be expected that the dominant channel will return to an alignment along the southern bank and
the erosion rate will increase. This will result in additional areas for which control lines are breached. It is conceivable that
over time the entire length of Noosa River Spit could be protected with rock walls and no beach would be available.

The potential impacts of Option B [establishing erosion limit control lines] include:
                •   Before control lines are breached - foreshore eroded with scarps and scattered with dead trees
                         •     Reduced opportunities for beach recreation and safe swimming
                         •     Safety issues [unstable banks in such a popular area]
                         •     Loss of Council pathways and established vegetation
                         •     Adverse public perception
                •   After control lines are breached - rock wall and deepening of seabed adjacent
                          •   No further erosion
                          •   Complete loss of beach
                          •   Complete loss of recreational amenity
                          •   Adverse public perception

Given the desirability to retain some recreational amenity in this area, it is not considered to be desirable to continue
pursuing this strategy. It is noted, however, that there are some areas where provision of a beach is not suitable or desirable
[e.g. at the end of the Noosa River Spit] and provision of a wall as a means of erosion protection will likely remain the most
appropriate solution in these locations.

Consideration was given to nourishing on the southern side of the Noosa River Spit adjacent to the location most vulnerable
to breaching [Figure 19] in an attempt to increase the time before erosion control lines are breached. Unfortunately, a large
section of Noosa River Spit is low-lying [submerged on higher tides] and will be more easily eroded. As the whole length
cannot be easily widened or raised due to the presence of mangroves, this would merely shift the most vulnerable location
and would not provide a recreational beach or reduce the erosion at the end of the Noosa River Spit.




       Nourishment to move erosion control lines




Figure 19: Option to widen vulnerable area of Noosa River Spit