Responses to community comments - inundation surveys

by kmarples,

Responding to comments received recent tidal inundation surveys during May/June and July 2020

Council carried out a community survey on tidal inundation during May and June 2020 as part of its Local Adaptation Planning work in Pelican, Blacksmiths, Swansea and Caves Beach.

Community members asked Council to comment/respond to the major themes raised in the survey. Please see example comments and responses below.


Acknowledgement of king/high tides and tidal inundation

“I have lived in Peel Street, Swansea adjacent to Black Neds Bay for almost 10 years. The worst I have seen this street affected by flooding has been small pools of water on the road. and, I have never been inconvenienced in any way or restricted”

“We have lived with a degree of inundation during King Tide periods and freak storm cells with the impact mostly affecting channel and lake perimeters”

Tidal inundation would cause much damage & inconvenience especially if it coincides with heavy rain for an extended period like April 2015 or when the “Pasha Bulka” was beached in 2007.

A: Council and the local community have records of tidal inundation during periods of king tides and when tidal anomalies take place (eg. trapped coastal waves or low barometric pressure). Areas impacted include the Swansea cycleway adjoining the Pacific Highway, Bowman Street (near Plains Creek Gully Bridge), Wood Street, Jonathan Street and Channel Street Swansea. Also, the car park and access road to Grannies Pool.

While the impacts associated are considered ‘minor’ by many at present, the frequency, duration and extent of this inundation is projected to increase over the coming decades. Council and the community are working together to help identify and manage current and future flood and inundation risks.


Dredging of the entrance channel

“I believe the best option is to dredge the Swansea channel and replenish the sand dredged from channel to local beaches or use it as road base for road projects.”

“Dredging of the channel and lake entrance full time is a must”

If you went to the expense of dredging the lake and Black Neds Bay then any water level concern would be much less. Put a brick in a bucket, what happens?

A: Dredging the channel has been shown to increase the amount of water entering the lake from the sea. This can worsen flooding in the channel and low-lying areas of the lake. Dredging can also lead to faster velocity of tidal flows in the channel which can worsen erosion/scouring of the bank. Dredging is primarily related to navigation access and is not a feasible strategy for managing flooding or projected sea level rise. For further information on the impacts of dredging on the channel and lake, please refer to the Lake Macquarie Coastal Zone Management Plan.


Keep drainage clear

“Storm water drains need to be kept clean at all times”

“Flooding occurs [at times] throughout the year depending on the season and the moon. All a part of nature. Maintenance of drains and gutters would go a long way to addressing the problem”

“Drains and clearing of creeks to insure run off into lake is paramount We use to live in Marks point and we experienced flooding which came from the road not the lake. Poor, blocked and ineffective drainage was the issue not sea rise. To my knowledge this is still the situation LMCC are not addressing the drainage issue. It seems to me they are looking to claim sea rise to be responsible not their failure to address what is a blatant failure over many years”

“I live in Bay Street. Our street endures rain water running in from Lake Parade / Catherine St / Moxey St towards the lake. Also, when the street gutters are not cleared by Council on an annual basis, the rising lake water backs up and our street floods regularly in addition to rain and storm water not able to get away. Our only drainage is into the lake”.

A: Council has a program to maintain local drains on an annual basis, or more twice yearly when assessed as a priority (for example, a number of low-lying areas around Swansea, Pelican and Blacksmiths). Poor drainage has been and will continue to be an issue in and around parts of Pelican, Blacksmiths and Swansea as the area is low-lying and very flat. The lack of fall in local streets means that inadequate grade is available to allow water to drain. This is exacerbated by a shallow groundwater table. The 2D Stormwater Model and report prepared by WMA Water in 2018/19 indicated that in many low-lying areas of Swansea, doubling the pipe capacity in the drainage network won’t be effective in reducing flooding as there is insufficient fall to convey drainage waters into the lake. The local adaptation plan currently being prepared will provide direction for alternative drainage solutions to be introduced in combination with and sequenced with other adaptation options.


Kerb and guttering

“Council should be planning kerb and guttering all streets in Swansea with the correct fall so water runs away instead of pooling, the soccer oval which fronts Pelican Street should be kerb and gutter as a matter of urgency. It is a disgrace in 2020 that LMCC does not planned to do this. This would ease the problem of flooding in various areas”

A: Poor drainage has been, and will continue to be, an issue in and around parts of Pelican, Blacksmiths and Swansea as the area is low-lying and as lake and sea levels rise so too will tidal, flood and groundwater inundation. Kerb and gutter has been used successfully in suburbs with higher elevation and enough slope to allow water to run off downslope. The grades in local streets in these areas do not allow for this to occur. The local adaptation plan currently being prepared will provide direction for alternative drainage solutions to be introduced in combination with and sequenced with other adaptation options.


Evacuation routes and Bowman Street flooding

“Bowman St will still need to be raised to allow residents to enter/leave Caves Beach soon! Already floods on high tides”.

“To exit or enter Caves Beach there is only one access point which is the junction of the Pacific Highway and Bowman St. This area is highly subject to flooding. In the event of any emergency this would mean that the rapid evacuation of Cave Beach would be impossible as well as emergency vehicles being unable to enter. A second access road is required and the upgrading and reopening of Scenic Drive to access the Pacific Highway would seem to be a reasonable solution”.

A: Council and community members preparing the local adaptation plan have been working closely with NSW State Emergency Service representatives. Emergency preparedness including identifying and maintaining suitable evacuation routes has been identified as an essential part of the adaptation plan.


Climate change mitigation – preventing sea level rise

“While there are many cities below sea level it is better to prevent inundation by rising sea levels because it may result in houses becoming uninsurable. Even slight temporary inundation suggested in many of the survey questions would cause inconvenience to everyone & have a negative impact on real estate values. “Prevention is better than cure” in this case”.

A: Council and the community have shown a high level of support for climate change adaptation and mitigation. While the local adaptation plan being prepared is part of Council’s climate change adaptation programs, there are a number of other programs seeking to mitigate climate change through reducing greenhouse gas emissions and energy and water conservation programs. For further information please refer to the recently adopted Environmental Sustainability Strategy and Action Plan 2020-2027.


Erosion at Blacksmiths dunes

“I walked along the beach at Blacksmiths on Friday morning last with a friend so that we could pick up plastic and rubbish that had washed up by the tide. It was alarming to see the erosion along the frontal dunes”.

A: Council and the community are aware of the episodic erosion of Blacksmith beach and dunes. Council is carefully monitoring erosion and damage caused. Options for monitoring and managing the beach and dunes now and in the future will be a key component of the Draft Local Adaptation Plan and Coastal Management Program being developed by Council and the community. For project updates, visit shape.lakemac.com.au/blacksmiths-beach-surf-assessment


Lake flooding options

“We live on the lake and suffer flood inundation from the lake. The options don't seem to address this”

“I was very puzzled by the options being considered in the current exercise - it seemed to be confined to Swansea's CBD, with no mention of any actions further west. It seems logical that some measures must be taken to block the encroachment of the lake, but no details were given - what barriers or other measures? , where?, all parts of the suburb or only selected higher ground?

A: Local adaptation planning options in the Feasibility Assessment and the Cost Benefit Analysis consider flooding and tidal inundation impacts and options for the foreshore areas of the lake and the channel, including lakeside residents and the Swansea economic centre (CBD). For more detailed information review the Feasibility Assessment Report, explore the document library and newsfeed on this project website or contact Council on 4921 0333.


Seawalls, Levees and Pumps

“Why don’t we raise our sea walls to form a protective barrier/levee bank?”

A: Raising our seawalls and building levee banks may be useful for high lake and ocean levels. However, seawalls and levee banks often exacerbate the impacts of local rain events. For low-lying suburbs this option is considered to be inappropriate as it does not address the impacts of groundwater levels rising during flooding events and the long term increase in the level of groundwater as sea and lake levels rise.

“Pump flood waters into storage”

“For Figure 4, Black Neds Bay West and SBD stages 1-4: this is going to cost a real lot of money and community disruption, particularly raising buildings and highway and Wood Street and Lake Road will still flood. Who will pay for this? Why don't you build the raised revetment (non-porous or course) and install pits and pump at the ends of the drainage lines. Will only have to pump when rainy and high tides/floods. Plus, you will catch all pollution in these pits. It would have to be cheaper than what it proposed”.

A: This option was considered as part of the feasibility assessment mentioned in the newsletter and is not currently supported due to the large volume of water generated during rainfall events. Storage capacity and pumps would need to be considerable. Pumps are often also at a high risk of failure during flood events. For further information please refer to the Feasibility Assessment Report.


Sewerage concerns

“The main problem we experienced during the flooding of June 2007 and April 2015 was not water over the roads but the fact that the sewer manholes were inundated and so Hunter water ceased to pump, meaning there was no proper sewer. A fix is a priority”.

“We arrived in Swansea in 2004 and have been severely inundated twice, being 2007 and 2015. On both occasions our entire block was covered to a depth of over 30cms, flooding our house's ground floor and our detached garage (which we had built to the 1-in-25-year flood level). Both times the flood water was contaminated by sewerage.

A: The combined Council and community working group preparing the Local Adaptation Plan have been liaising with Hunter Water representatives about the development of the Plan. Hunter Water has advised “Climate change presents significant challenges to the way we manage our water and wastewater infrastructure”. Hunter Water programs related to climate change action are available here: https://www.hunterwater.com.au/our-water/sustainability/climate-change-action


Personal history/account of flooding in area:

“Resident of the area for the past 45 years so I have seen some major flooding & inundation hence my acceptance of some natural interference with everyday life.”

“Worst storm at Pelican was over 30 years ago when bulk carrier Signa washed up on Stockton Beach. Water covered Pelican Park and Lake View Parade to 400mls for about 4 hours but receded by 9am. Nothing since last 30 years.”

“20 years, despite big storms, heavy rainfall and high tides, this has never breached the breakwall of my property. I live between Swansea and Black Neds Bay.”

“From my 70+ years association with Swansea, flooding has been caused by stormwater in the catchment area and not sea level rise.”

“Swansea has always had flooding and high tides. Why should we bother with this project?”

A: The largest recorded flood in Swansea occurred in 1949 and measured around 1.2m AHD. Other large flood events occur approximately every 10 years (recently 2007 and 2015). The Signa storm in the 1970’s was one of our highest recorded events.

A 1% AEP (annual exceedance probability) event is a very large flood with a probability of 1% (1 in 100) of occurring in any one year. Tide gauges at Swansea, Belmont and Fort Denison (Sydney) show that sea and lake levels have risen at around 2.5-3mm per year over the last couple of decades. This rate of rise is predicted to increase over the next few decades. The local adaptation plan is looking across 10, 50- and 100-year planning horizons. We are planning for the worst, hoping for the best, and only acting when necessary.


Property Prices and Insurance Premiums

“Is this work going to devalue my house/property?”

A:Many factors affect the property market and the individual choice of buyers, including interest rates, the health of the economy and the desire to live in a particular location. Studies of the value of property in flood affected areas here and overseas show some consistent patterns:

  • There is already a discount built in to the market for properties that are known to flood
  • Even in known flood areas, other factors such as aspect, views, and direct water frontage are strong drivers of value
  • After a major flood or other disaster prices may drop (typically 5-10 per cent) but generally recover after one or two years

New information such as flood conditions being made publicly available (such as Brisbane’s ‘Floodwise’ program) can cause a drop in prices (about six per cent in Brisbane) but they generally recover after one or two years.

Council reviews independent annual property market reports from the Real Estate Association of Australia and compares 10-year profiles with non-low-lying suburbs. Recent figures show that there has been an increase in the number of units and villas in Swansea and that sales in Pelican and Blacksmiths are trending similar to other suburbs across the local government area.

By planning for the worst, monitoring and responding to recognised triggers only when required Council and the community can help reduce uncertainty of housing prices in potentially impacted areas.

“Won’t this work drive up my insurance premiums?”

A:Insurance is provided for the period of the premium (typically one year) and for a specified event or hazard, not for a gradual process such as sea level rise. Therefore, the level of a lake, river or the sea in 20 or 50 years’ time should have no effect on the premium calculated for the current year.

Flood insurance has only been widely available on the Australian market since 2009. Prior to that, information about flood hazards in Australia was considered so poor that most insurers were unwilling to provide insurance. As state and local governments complete more high-quality flood studies, insurers can more confidently judge the risk and offer appropriate cover.

Flood levels are predicted to rise with projected sea level rise – and the number of houses impacted by flooding will also increase. As this happens, a naturally accompanying increase in premiums may occur. This is not caused by adaptation planning. It is hoped that adaptation planning will help to reduce future impacts and minimise insurance premium increases.

Council liaised with the independent Insurance Council of Australia to better understand how insurance is calculated for Australian insurers.


Raise and fill options

“Swansea needs to be built up at least to 450mm above current high-water level, all new builds should conform to that, current floor levels must remain. This is expensive but I believe it's the only way to save Swansea and I feel would be enough to keep the suburb open even in bad weather”.

“My house cost me about an extra $20,000 for foundations to cover future flooding”

A: The current Flood Planning Level is 2.36m AHD, which takes account of the current 1% AEP (annual exceedance probability storm – similar to a 1-in-100-year storm occurring in any one year), sea level rise and a safety margin (called freeboard). This ensures that a house built today is more likely to stay “high and dry” over the commonly adopted asset life of 50 years.

“To do rebuilds are up for huge costs to cater for flooding and yet the Council intends to get the highway and business area built up (who's cost). So the council would be better off building a large lock in Swansea channel instead of doing all these build ups and higher floor levels for all housing etc. because the streets will be flooded and we won't be able to drive around any way.”

A:Council and the local community are currently examining a range of options to manage flooding and tidal inundation into the future. Building a lock in the entrance channel was considered in the feasibility assessment undertaken as part of the project. The option was deemed not feasible at the current time as a result of technical feasibility and cost. Review the Feasibility Assessment Report for further information. A shortlisted range of options was advanced to the Cost Benefit Analysis, which is currently being undertaken and results will be available on the project website shortly.

“Why doesn’t Council start “ramp” filling Swansea now?”

A: While filling in some low-lying areas can assist with nuisance drainage and flooding – large-scale filling would impact existing roads and properties and might exacerbate the problem. It is understood that future filling of land will take place on an as needed basis – please refer to option AC1 (raise and fill) in the cost benefit analysis options list. Any filling/raising of land needs to be carefully timed and sequenced with other local adaptation planning options.


Swansea Holiday Park

“With Swansea caravan park headed for inundation & possible relocation to elsewhere in the City, why is so much money being spent on infrastructure in the park i.e. swimming pool, cabins etc?”

A: As part of the cost benefit assessment (CBA) being undertaken as part of this local adaptation plan, Council is looking two alternative options for the Swansea Holiday Park: i) to raise and fill the park, and ii) to relocate the park. The CBA results will be of interest in planning for the long-term future of the holiday park. In the short-to-medium-term, Council has developed strategic and operational management plans for all of its holiday parks. These plans have been informed by ongoing local adaptation planning in areas susceptible to flooding, tidal inundation and projected sea level rise. Much of the infrastructure in holiday parks is considered movable and as such adaptable to future impacts that may take place in 20-30 years or more. Council’s investment in more permanent infrastructure is informed by a business case considering costs and benefits over the projected asset life cycle.


General comments questioning the survey:

“The survey seems not to separate the difference between flooding of the lake and possible rise in mean sea level”.

“Any local tidal disruption would be 2-4 hours max. The 24 hour + scenarios above relate to flooding due to heavy rain and not tide”.

A: The survey was seeking community tolerance responses for flooding impacts caused by tidal inundation and/or lake catchment area flooding.

“Having noted ‘Never’ in answering questions; I realise when we have super storms and natural events this is unavoidable”

“See hard copy and adapt: qu. 6: 1 in 10 years qu 7: 1 in 10 years Qu 8: 1 in 10 years qu 9: 1 in 10 years qu 10. 1 in 25 years qu 11: 1 in 100 years. ie: i feel you should have had a 1 in 10 years and 1 in 25 years column as well so i put those occurrences in the never column.”

A: This was a very valid point about the frequency options available in the initial survey conducted in May/June. It prompted the project to conduct a follow-up survey (in July) to investigate the community’s tolerance for impacts that didn’t occur annually but occurred in less frequently intervals such as once in five, 10, 25, 50 or 100 years. This survey has now concluded and received 168 responses. An engagement summary will be available soon.

“The question asked about restricted access is via car or pedestrian?”

A: The intent of the question was relating to all forms of access that you predominantly use.

“Never not practical due to cost benefit to community. The answers are very dependent on the cost ratepayers re works programmes to reduce/eliminate impacts. If the questions were qualified by the expected impacts on other Council funding, then you would receive a much different outcome!!”

A: A shortlisted range of options was advanced to the Cost Benefit Analysis, which is currently being undertaken and results will be available on the project website shortly. A key part of this analysis is to determine the distribution of costs and to identify the parties who benefit from the adaption works. Stay tuned to this project website to keep up to date with the latest local adaptation planning information and cost benefit analysis reporting.


Mud Creek and Wyee Bay

“Drainage has to be addressed and effective: we live on Mud creek which is blocked by foliage and trees falling into creek and blocking the creeks’ run off into the greater lake. The clean-up of these creeks is a must to reduce flooding. The road bridge across Mud creek causes a problem Hunter water ran gas pipes across Mud creek which is lower than the road bridge cutting access off to the greater lake and adding to the possibility of extremism flooding in a proclaimed and known flood area How can this happen.”

“The tidal inundation and erosion to our local lake’s foreshore is slowly claiming more and more of the Wyee Bay shoreline. A combination of our predominant NE winds combined with the increasing big tides, with no sea wall protection is a problem.”

“Prevailing North Eastern winds driving the lake to erode the banks on the reserve of Wyee Bay. 4-6 metres in areas in 10 years.”

A: These comments refer to areas outside of the local adaptation plan for Pelican, Blacksmiths, Swansea and surrounds. We have passed on these comments to the Lake Macquarie Coastal Management Program being developed 2020-21 and will also retain information for the proposed Fennel, Edmunds, Kooroora Bay Local Adaptation Plan, pending outcome of recent floodplain management grant application. Follow and contribute to the Lake Macquarie Coastal Management Program community consultation at shape.lakemac.com.au/coastal

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