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

Figure 15: Critical times for erosion

In the medium-term, it is likely that periods of calm weather will result in increased meandering of the river and the southern
channel will once again become the dominant channel. This will result in increases in the velocities adjacent to the foreshore
and a corresponding increase in erosion rates, potentially greater than the average rates between 2006 and 2009. While it is
possible that meandering will result in a northern channel alignment, the extensive flood delta [Figure 12] and the
predominance of the southern channel in the past [Appendix A] indicates that a southerly alignment is much more likely. In
the event that a northerly channel develops or a major event results in a reinforcement of the middle channel, the
development of the southern channel may be delayed. As such, it is likely that erosion in this location will continue, although
given the extent is difficult to predict.

From the high rates of erosion [averaging 10m/yr, but potentially higher] and the narrow width of the Noosa River Spit [70m,
some of which is low-lying], it is clear that in the Noosa River Spit could potentially breach in the medium-term. On average
rates, this would be expected to be within 5-10yrs, however the high variability of the system and the potential impact of
major events could have a substantial impact on this timeframe. Breaching would introduce the potential for redevelopment
of a Noosa Sound channel which would have significant ramifications on estuary dynamics [Figure 16]. Long-term widening
of the breach could result in eventual loss of the Noosa Spit. In the long-term, if no protection works are undertaken,
narrowing and breaching of the Spit along the beachfront is also conceivable [Figure 17]. The impacts of breaching of the
Noosa River Spit are potentially substantial. It is noted that reinstatement of the Noosa River Spit would be a substantial
undertaking, particularly if it involves closure of a dominant channel.

Erosion at the end of the Spit is also likely to continue and this would result in increased wave penetration into the estuary,
particularly to Munna Point [Figure 18]. This could potentially have an impact on erosion in this area. Management of this
location may need to be considered if erosion at the end of the Noosa River Spit is allowed to continue.




                                                                      -A& A
Figure 16: Potential channel alignment in the event of breaching of Noosa River Spit