2021-01-27 Special Meeting Agenda

SPECIAL MEETING AGENDA                                                                27 JANUARY 2021


However, flooding within the playground is characterised by higher flow rates and greater depth.
The site is extremely flood constrained and could be characterised as being part of the floodway
(i.e. an area of active flood conveyance during a flood event). The flooding characteristics at the
site can be summarised as follows:
       The majority of the site floods for even the 50% AEP event (i.e. 50% chance of flooding each
        year). Floods more frequent than this have not been modelled
       Flooding reaches unsafe conditions over much of the site in even the most frequent flood
        modelled (50% AEP)
       Flooding occurs rapidly, with as little as 13 minutes from the start of the event until the site
        begins to inundate, while the time from the start of the event until the southern-most pathway
        (evacuation route) begins to inundate is 39 minutes
The applicant’s flood modelling concludes that
       Proposed flood depths for the 50% AEP range from 0.25 m along the western boundary up
        to 2m within the vegetated open channel in the middle of the site.
       Proposed flood depths for the 1% AEP in the year 2100 range from 0.5 m along the western
        and over 2m within the vegetated open channel in the middle of the site.
       A maximum rate of lateral spread (velocity) of approximately 0.05m/s
These characteristics present clear issues for both infrastructure located in the park and also the
safety of park users. The applicant has addressed infrastructure lifecycle costs by advising that
they accept and have budgeted for the likely cost burden associated with this frequent flooding, so
the remainder of this review focuses on the safety of people.
Council’s consulting hydraulic engineer is of the view is that…..
    the proposed use as a playground is incompatible with the nature of the sites flood constraints,
    as the proposal will actively encourage people (including children) to congregate in an area with
    known flood risks. For all flood events modelled, the majority of the site will have a degree of
    hazard which makes it unsafe for children and the elderly. This includes events as frequent as
    the 50%AEP (i.e. 50% chance of occurring in any given year).
    To put it simply, if a child or an elderly person remains on site during even a minor (50%AEP)
    flood event, in the majority of locations on the site they will be at risk of serious injury or death.
    It is therefore incumbent on Council as both the proponent and assessment manager to be
    confident that there is no reasonably foreseeable likelihood that the public will remain on the
    site during a flood event.
    Elimination of the flood hazard at the site is not possible, as filling the site to eliminate the hazard
    would cause off-site flood impacts (i.e. worsen flooding conditions elsewhere).
    To address the risk to people, the applicant has submitted a revised Flood Risk Assessment
    and Emergency Management Plan (FRAEMP) (Bligh Tanner, January 2021) which includes
    proposed marked-up modifications to the playground design (refer Figure 18). These proposed
    modifications have also been incorporated into the flood modelling results presented by HWMC
    (July 2020).
    The risk to people has been addressed in the FRAEMP through the following strategies:
          Discretionary visitation to the site (i.e. relying on people not attending or staying at the
           park during rain)
          Signage
          Self-evacuation




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