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Nic
Peet introduced the session. Chris Dolley explained the workshop as a
starting point for developing a strategy for flood resilience in the face of
a fast-changing climate. Discussions covered:
·
An
overview of the history of key decisions including 2015, 2018 and 2021 LTPs,
with slow and steady approach to making improvements and asset replacements
at key sites.
·
Levels
of service and levels of protection are modelled and account for things like
slash through freeboard. Bridges were not normally included in modelling in the
past. Linked in to TREC through Waka Kotahi and others highlighting the
impacts of bridges on other infrastructure and the need for bridge design to
change given the Cyclone Gabrielle event, e.g. higher, longer span. Specifically,
have discussed the Awatoto rail bridge with Kiwirail and stressed the need
for a better-designed replacement for the temporary bridge that’s in
place now.
· Modelling for over-design events has
been done, including a failure mode analysis done of the Heretaunga
Scheme done in the 1999 which articulated what might happen (where would the
water go) in an over-topping or failure event. Some scenarios played out in
Cyclone Gabrielle but others didn’t. Also, currently T+T is running over-design
event modelling, including a 500-year post-Gabrielle event in addition to
probable maximum flood.
· One potential improvement to
Council’s information-sharing is to make more of this type of work
(1999 report) available to the public via the hazards web portal.
· More meaningful
‘measures’ need to be used to communicate the level or severity
of river flows/ floods.
· Models have been updated with the
Cyclone Gabrielle data, and going forward, modelling is being used to
determine where the most significant issues are likely to occur and identify
a wide range of options for how to mitigate against those failures happening.
· Understanding the flood plain as a
whole and having thresholds is key to future response management– through
a flood plain management plan. These flood plain management plans would
include areas of risk and thresholds for when action needs to be taken, e.g.
evacuations.
· Had the forecast data for Cyclone
Gabrielle from MetService been accurate the flood models would have shown the
flooding that occurred and the response by CDEM would have been much
different and potentially tens of thousands of people would have been evacuated.
·
Have
new flood forecasting tools that run in the background 24/7.
 ç next 3 years work
· Very good knowledge and experience
base in HB, or in NZ. The Dutch model comes up often, and have looked at
using in the past however very expensive. National tax funds hundreds of
millions of dollars of maintenance work which is simply unaffordable for NZ.
Philosophy is all about protecting people and buildings and they have moved
whole rivers to protect communities, which doesn’t ‘mesh’
with the NZ view of ‘giving rivers room’.
·
Modelling
of future events, factoring in climate change, is being done.
·
The Flood
Plain Management Plan (to be developed) will be community focused and talk
about the risks and options for interventions to mediate those risks and
strongly connected to the districts and their District Plans, including how
communities can interact with warnings and alerts. These will replace the
technical, internal looking documents we currently have.
·
Tonkin
+ Taylor modelling being done for overdesign events (500yr, post-Cyclone
Gabrielle) including secondary flow paths, detention of flood waters, room
for the river and nature based solutions. Challenge will be how HBRC engages
with the community on a wide range of solutions/interventions as part of the
plan into the future. Will work with T+T to share their work with the
independent flood scheme performance review panel and potentially present to
council in a month or so.
· Key point is that if you live on a
flood plain there are interventions that can be made/built, but they all have
limits.
· Rules around evacuation include that
it must be done in daylight and you must allow sufficient time.
· T+T is also investigating the costs
associated with interventions.
·
Before
the deluge – the sector’s business case to government for
investment in flood resilience is currently with the government for consideration.
HBRC has not sought more funding in addition to the $250M we already need to
deliver on, however still actively involved in Crown funding discussions.
·
$3M
has supercharged the scheme review programme from 10 years be completed by
2026, with those reviews ultimately bound to identify additional investment
required.
Martin
Williams left at 12.22pm
·
The
(Raikes) report that John Bostock tabled during the Revenue & Financing
Policy Review hearing has been provided to the independent flood scheme
performance review panel and to T+T.
·
The
following slides highlight the evolving picture associated with flood
resilience.
Martin
Williams rejoined the meeting online at 12.25pm.
·
Urban
stormwater networks are the responsibility of the district and city councils
and taking account of those in district plans. Stormwater networks interact
with flood schemes when they run into rivers.
· Scheme reviews for smaller schemes
include engagement with those communities, however there has been a tendency
to keep costs low to the detriment of the scheme, e.g. maintenance work not
done because it was deemed too expensive by the community. Expect that there
will be recommendations for significant funding to bring some of the smaller
schemes back up to acceptable levels of service – not just for current
landowners but for all generations.
·
Status
of scheme reviews is:
 
 out to market and will all be
completed by the end of 2026
·
Looking
at ways to provide value include:
·
T+T
report on the Tukituki review recommended gravel extraction to a greater
extent and a contract for tender is going out next week.
·
Need
to make programmes of work and their timeframes visible internally and to the
community.
 small forests for
wastewater discharges
·
T+T
presented their work to date on the Upper Tukituki review and HBRC has
already commissioned the removal of gravel in front of Waipawa, plus a couple
of areas have been identified where the river is perched and changing the
grade line is recommended.
· It was suggested that community
engagement needs to start with the question “what should we do for
flood resilience”? rather than proposing solutions for the community to
comment on. Resourcing will have to be scoped with the comms & engagement
team.
· If this is going to be
Council’s number one strategic priority, the conversations will come
after the LTP. Getting from present to future, the elements are 1. Evidence
gathering, 2. Develop the proposed approach to future resilience with
engagement with the community, leading to 3. Decisions (2027 LTP). The $250M
Category 2 work will be running parallel. A timeline will be developed.
· All infrastructure providers are
sharing information and working together, particularly through the Regional
Recovery Agency infrastructure pou.
·
Important
to promote future workshops as a means of providing the community with
information about what the Council is doing and where work is at.
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