2018-05-14 GC Agenda Attachment 1 to Item 6 Lake MacDonald Dr Community Reference Group Investigations Report

7.2       Council considerations for mitigation options
The above mitigation options explored by Council to investigate possible relief of flood depth and
extent within the area surrounding Liane drive have provided results which need to be evaluated
within a consistent framework across the entire Shire.

When considering flood mitigation options within the Shire, the Council is required to evaluate each
option for its effectiveness for the local flooding area and its value within the context of the entire
Shire. In order to do this the Council must first perform a risk assessment of any affected land
parcels within the Shire. The framework for doing this work is set out on State and National levels
and would assess each land parcel for the consequence of a natural disaster, in this case flooding.
Typically these assessments evaluate each parcel of land by assessing:

    1. Loss of life. What is the potential loss of life for a given event in this area?
    2. Financial and Economic. What are the impacts to the local/state economy from a given
       event?
    3. Community & Social. What are the impacts to places of cultural significance and community
       cohesion?
    4. Public Administration. What is the ability of the governing bodies to cope with a disaster of
       this magnitude?
    5. Environmental. What is the damage to natural resources, ecosystems or species?

Once this risk assessment is conducted across the Shire, Council would consider potential
mitigation options within the context of the following questions to assess the effectiveness and
viability of each option:

    1.   What are the positive consequences to providing this mitigation?
    2.   Are there any negative consequences to providing this mitigation?
    3.   What are the cost implications for this mitigation option?
    4.   What are the environmental implications of this option?

With relation to the mitigation options provided in section 7.1, an assessment of each option is
provided in table 1 below:

Table 1: Mitigation Option Assessment

Option              Positive                Negative                 Estimated Environmental
                    Consequences:           Consequences:            Cost      Considerations
                    Flood level reduction   Flood level increases    ($AUD)
                    for Liane Drive         in adjacent areas.
                    (mm)                    (mm)
1: Low Earth        100-250                 500-1000                 250k         Low if no clearing
Bund                                                                              is required and
2: High Earth       100-250                 >1000                    630k         built on private
Bund                                                                              land or road
                                                                                  reserve
3: Single           0                       0                        1.5M         High due to
Channel                                                                           clearing and
4: Double           0                       0                        2.8M         disruption of
Channel                                                                           sensitive habitat
5: Combination      100-250                 >1000                    3.7M

Given the limited benefits, consequences to adjacent land parcels and large costs involved with
each of these options, Council is unlikely to proceed with any of these options.




Lake McDonald Flooding Community Reference Group Report                                        Page 31