This Floodplain Risk Management Study and Plan for Mona Vale/Bayview has been
undertaken by Cardno Lawson Treloar for Pittwater Council to identify and examine options
for the management of flooding within the Mona Vale Main Drain and Cahill Creek
floodplain. The study has been undertaken in accordance with the NSW Government
Floodplain Development Manual (2005).
A locality plan can be found in Figure 1.1. The outline of the study area can be found in
Figure 1.2.
Study Context
This study forms two of the multiple stages of the Floodplain Management process which
includes:
- Formation of a Committee
- Data Collection
- Flood Study
- Floodplain Risk Management Study
- Floodplain Risk Management Plan
- Implementation of Floodplain Risk Management Plan.
The study was jointly funded by Council and the Department of Environment and Climate
Change. The Department also assists in the provision of specialist advice on flooding and
related matters.
Findings of the Floodplain Risk Management Study
The investigations and consultation undertaken as part of the Flood Study (DHI, 2002) and
the Floodplain Risk Management Study (Chapters 1 to 9) identified a number of issues for
the floodplain. Based on these issues, a series of floodplain management measures were
developed.
The assessment of management options provided in this study facilitates the identification
of the most beneficial options (in terms of hydraulics, economics, environmental and social
issues). The outcomes of the Floodplain Risk Management Study (summarised in the multicriteria
matrix outlined in Section 8.3) were utilised to develop this Floodplain Risk
Management Plan. Public consultation will be undertaken during the exhibition of this Study
and Plan. This additional consultation and review will lead to the refinement of this study
and the final recommended floodplain risk management options for implementation.
Those actions with a rank equal to or greater than 20 (Appendix H) have been included in
the actions for implementation, except for those options which conflict with a higher ranking
option. Where two options with the same ranking were recommended for the same
location, the option with the higher benefit:cost ratio was included in the plan.
The Plan
The plan consists of a mixture of:
- Property modification actions
- Emergency response modification actions
- Flood modification actions
- Climate change adaptation strategies.
Table 10.1 summarises the highest ranking options which are recommended for inclusion
in the Floodplain Risk Management Plan. The plan is also shown in summary form in
Figure 10.1. Those options selected for inclusion in the Plan are based upon both their
likely benefit and the funding available from Council and the State Government.
A total of 19 options have been proposed for inclusion in the Floodplain Risk Management
Plan. The estimated total capital cost of implementing the Plan is $10,503,000 with a
recurrent annual cost of $77,000.
