Lower Wyong River Floodplain Risk Management Study

A number of conclusions can be drawn from the Floodplain Risk Management Study which lead to
inclusions in the Floodplain Risk Management Plan. These conclusions are as follows:
- The study area (Wyong River and Mardi Creek from Woodbury's Bridge to a point 1.4
kilometres upstream from Tuggerah Lakes) covers some 18.34 sq kilometres. Thirteen(13)
percent of the study area is zoned “Wetland Management Zone” while ten (10) percent is
zoned as “Open Space”. The remainder is generally cleared and used for residential,
commercial/industrial uses and agriculture (grazing).
- There are 404 houses on the floodplain with floor levels below the 1% AEP flood level.
- There are 148 commercial and light industrial premises on the floodplain.
- The total average annual flood damage is some $9.22 million. The ranking of the
contributions to flood damage are:
- Commercial/Industrial: 82 percent
- Public Utilities: 11 percent
- Residential: 7 percent
- The commercial/industrial damage is virtually all sustained in the Tuggerah Straight
Industrial Area.
- Wyong Shire Council's development control has been based on their Flood Prone Land
Development Policy (circa 1986). The increase in buildings on the floodplain in the past 15
years suggests that the Policy is not achieving its objectives of minimising the financial and
emotional cost of flooding.
The Flood Policy should be updated and incorporated into a Development Control Plan.
The creation of the DCP and its public exhibition will provide greater public awareness of
floodplain management and will have greater standing in the Land and Environment Court.
It is understood that the development of such a DCP is currently underway.
- The Lower Wyong River has an operational flood warning system, though it has not been
tested in a large flood. Similarly, the general lack of floods has the potential to create a
situation where on-going maintenance of the flood warning system and infrastructure is
overlooked.
- The 2005 Floodplain Development Manual introduces concepts of:
<ul>
<li>flood risk;</li>
<li>flood modification, property modification and responses modification measures to mitigate flood risk;</li>
<li>flood planning levels (FPLs) based on a design (or historical flood) plus an
appropriate freeboard; and</li>
<li>the PMF event as the measure to classify "flood liable land".
A variety of flood modification and property modifications have been examined as ways to
address existing flood risks. Other than works in Mardi Creek (which have been virtually
completed), none of the measures examined are attractive in terms of capital required,
reductions in flood damages, or by benefit/cost analysis.</li>
<li>Continuing flood risk occurs through the continued existence of development in the flood
liable land areas, while, essentially, future risk relates to future development.</li>
<li>The principal mechanism for managing continuing and future flood risk is via development
controls.</li>
<li>Council's current development controls for flooding derive from the Flood Prone Land
Development Policy, dated circa 1986. The Policy should be incorporated into a
Development Control Plan and modified with regard to the freeboard requirements, the
development types covered and criteria adopted.</li>
<li>Additional measures appear warranted for rural residential development in the area.</li>
<li>Changes to the Main Northern Railway Line and the Pacific Highway have the potential to
significantly increase flood levels. The impacts on flooding of the recent significant road
works along Tuggerah Straight by the RTA are unknown. Whilst this infrastructure is
owned and operated by other government instrumentalities, Wyong Shire Council should
continue to monitor works on the infrastructure links.</li>
<li>The vulnerability to flooding of the Wyong Nursing Home has been a source of on-going
concern to Wyong Shire Council, however, the flood warnings for evacuation are now
issued by the SES and the evacuation of residents (should the need arise) appears more
likely . In this situation, the appropriate action for Wyong Shire Council is a continuing
dialogue with SES and the Nursing Home to ensure adequate warning and evacuation
measures remain in place.</li>
<li>The lack of floods in the past 20 years has diminished the general public's awareness of
flood risk. This should be addressed by a public education program. A revision of the
Flood Liable Lands DCP would assist in this regard.</li>
</ul>

Tags: Lower Wyong River, Wyong
Organization: Central Coast Council