Addendum Agenda of Shoalhaven Natural Resource & Floodplain Management Committee

Addendum Agenda - Shoalhaven Natural Resource & Floodplain Management Committee – Wednesday 18 April 2018

Page 4

SN18.9 Technical peer review of the River Road Foreshore Shoalhaven Heads: Assessment of the Coastal Management Options Report by MHL.

HPERM Ref: D18/75302

Group:

Section: Environmental Services

Attachments: 1. MHL Technical Review

Purpose / Summary

To advise the Committee of the technical peer review by Edward Couriel from Manly Hydraulics Laboratory (MHL), of the River Road Foreshore Shoalhaven Heads: Assessment of the Coastal Management Options Report prepared by Water Research Laboratory (WRL) UNSW.

Recommendation:

That Council

1. Receive the Manly Hydraulics Laboratory technical review of the WRL River Road Coastal Option Report titled MHL2595 – Review of River Road Foreshore, Shoalhaven Heads: Assessment of Coastal Management Options Report dated February 2018, for information; and

2. Subject to availability of funding, incorporate the following technical information in the detailed design of any future coastal erosion remediation control structure at the River Road foreshore precinct:

a. Coastal erosion remediation structure be designed for a more conservative large river entrance opening to reduce the risk of failure.

b. A minimum design life of 25 years for coastal erosion remediation structure be adopted.

Options

1. As per the recommendation.

Implications: Proceeding with the option endorsed by MHL‘s technical review, to undertake design incorporating the above technical information as per the MHL technical review recommendation. Designing the foreshore erosion remediation structures to a minimum design life of 25 years and for a large river entrance opening is likely to increase the cost of the structure. This will need to be costed as part of the detailed design process.

2. Recommend alternative options for the detailed design of the River Road coastal foreshore erosion remediation.

Implications: This would depend on the alternative option.

Background

The 2016 east coast low storm resulted in a moderate flood (Natural Disaster declared 2016) and a major coastal storm which impacted beaches and foreshores across the City.

This impact included coastal erosion of 1000 meters of riverbank on the Shoalhaven River at River Road, Shoalhaven Heads. In response to this erosion at River Road, Council engaged the University of NSW Water Research Laboratory (WRL) to undertake an assessment of the coastal management options to manage this erosion.

In August 2017, WRL produced the River Road Foreshore, Shoalhaven Heads: Assessment of Coastal Management Options, Technical Report, prepared by their team of experienced coastal and estuarine engineers.

The technical report divides the foreshore area up into six (6) prioritised zones based on coastal hazard and geo-technical risks impacting each zone. The study identified nine (9) management options:

1. Do nothing

2. Monitoring with no active management works

3. Monitoring in combination with management works

4. Relocating existing sand located within the beach area

5. Stabilisation of erosion scarps and revegetation

6. Protection structures (rock or geotextile revetment)

7. Repairs and improvements to stormwater outlets on the beach

8. Improvements to stormwater control across the beach

9. Nourishment of the beach

The report recommends which of the nine (9) foreshore management options are best suited to each foreshore management zone, as outlined in the figures below.

Figure 1: Qualitative Prioritisation of the Foreshore Management Zones

Figure 2: Suitability of Management Options for the Foreshore Zones

Consultation on the WRL technical report has was undertaken with the Shoalhaven Heads Community Forum members, Shoalhaven Heads Estuary Taskforce and the Shoalhaven Heads community.

The community identified the need to address and manage the storm water impacts and maintain the visual amenity.

Stormwater management and discharge is Council’s Asset and Works priority and a specialist stormwater design is needed with soft engineering options to be included. These conditions will provide erosion remediation of the whole frontage in one project, as requested by the community.

Upon the communities’ request, Council sought a technical peer review of the WRL report and engaged Edward Couriel, Director, Manly Hydraulics Laboratory (MHL).

MHL are the technical arm of NSW Public Works Division. Edward Couriel is a qualified Coastal Engineer and has over 20 years’ experience in coastal and estuarine engineering studies and is well placed to provide a pragmatic coastal engineering review of the WRL Technical Report. A copy of the MHL report is contained within Attachment 1.

The review recommends that a larger entrance scenario be adopted for the design of erosion control structures, as discussed in the WRL options report. The design modifications are expected to have a minor construction cost increase and an improved asset class and lifespan.

MHL also recommended that Council undertake a comparison of the life cycle cost and benefits of the WRL recommended 10-year design life of the erosion control structure compared with a longer serviceable life cycles of 25 and 50 years.

The peer review also highly recommended beach nourishment to some degree, as part of any longer-term foreshore management options adopted. As this may be warranted due to the potential benefits and cost savings of this management option, given the extensive environmental approvals associated with the sand nourishment options, the peer review recommended exploring sourcing sand behind the river entrance flood notch, where a “wet notch” was trialled in the 1990’s.

It is recommended that this option be reviewed as part of the 2018 Lower Shoalhaven River Flood Risk Management Study and the associated review of the Shoalhaven River Entrance Management Plan.

If this is a viable option, it would provide, along with the maintenance of the dry flood notch, a moderate sand supply for repeat sand nourishment to the River Road foreshore areas and potentially extend the “life of the next entrance breakout”.

Community Engagement

Extensive community consultation has already taken place in the development of the WRL foreshore management options report via the Shoalhaven Heads Estuary Taskforce and the Shoalhaven Heads Community Forum and at a community drop-in session at the Shoalhaven Heads community centre on Sunday 9 April 2017.

The community identified the need to address stormwater management and retain the visual and recreational amenity of the River Rd foreshore in any management options undertaken.

Members of the Shoalhaven Heads Estuary Taskforce requested Council obtain a technical peer review of the WRL report by another suitably qualified and experienced coastal engineer to assess if the recommended management options outlined in the WRL report are the best possible options. This technical review was completed as described above.

Financial Implications

In October 2017, Council, in consultation with the Shoalhaven Heads Community Forum, applied to the NSW Regional Growth – Environmental and Tourism – Restart NSW grant program for $1, 588,000 to undertake the coastal erosion management options recommended by WRL. Of this $1,588,000, Council would be contributing $550,000 for the storm water management works, rock protection and revegetation works. The cost of the peer review undertaken by MHL was $2,500.

The MHL peer review recommends designing the foreshore erosion remediation structures to a minimum design life of 25 years and for a large river entrance opening. This is likely to increase the cost of the structure, as larger sized rocks will be required. This will need to be costed as part of the detailed design process.

Addendum Agenda - Shoalhaven Natural Resource & Floodplain Management Committee – Wednesday 18 April 2018

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SN18.10 Undertaking a Scientific Analysis of the Shoalhaven Dredging Program

HPERM Ref: D18/80719

Group: Planning Environment & Development Group

Section: Environmental Services

Purpose / Summary

To provide information on what scientific indicators could be used to undertake a scientific analysis/study of the 2016 Shoalhaven Citywide Dredging Program.

Recommendation

1. Receive the report for information; and

2. Include the development and implementation of a scientifically based environmental monitoring and evaluation program in the project brief and design of any future dredging projects and other large-scale Council projects. This will ensure that:

· the implementation and success of projects can be monitored and evaluated;

· reduce the risk of failure of environmental controls and mitigation measures and potential increased project costs;

· ensure compliance with legislative obligations; and

· learn valuable lessons for future projects to avoid and minimise potential environmental and community impacts and therefore save resources, time and money.

The scale of an environmental monitoring and evaluation program would be dependent upon the scale of the proposed project and potential direct and indirect environmental impacts.

Options

1. As recommended.

Implications: The development and implementation of a scientifically rigorous environmental monitoring and evaluation program for any future dredging projects will need to be included in the project brief to ensure resources and budget are allocated. The number of parameters included in and the size of the program would depend upon the scale of the proposed project, its location and potential environmental impacts.

2. Council propose alternative recommendation

Implications: Would depend on the recommendation

Background

At the Committee meeting of 22 November 2017, the Committee resolved:

“That Council staff consider the Shoalhaven Natural Resources and Floodplain Management Committee’s request to undertake a scientific analysis of the dredging and report back to the Committee on how staff can undertake this and how the University of Wollongong can be incorporated into this.”

In 2016, Council undertook the following dredging and creek/dune protection projects:

· Currambene Creek Navigation Channel (removal of a small quantity of rock only);

· Sussex Inlet Navigation Channel;

· Sussex Inlet Canals (Rivera Keys Estate);

· Lake Conjola Configuration Dredging; and

· Mollymook Beach Dune Protection (Blackwater Creek).

The Shoalhaven Dredging Project, Review of Environmental Factors (REF), prepared by Royal Haskoning DHV (2015), recommended the monitoring listed below. The main aim of the REF was to design the project to avoid direct environmental impacts. The purpose of the creek and dune protection works was to restore eroded dune and foreshore areas and protect assets.

Monitoring of dredged areas – Using hydrographic surveys to monitor the dredge area prior to and immediately following the dredging works to determine the dredge depth and width. The REF recommended that these hydrographic surveys be continued biannually for the first year and annually for the following four years to assess the changes in sediment composition and changes in the dredge channel morphology.

Monitoring of nourishment areas – Surveys of nourished areas at Lake Conjola, Sussex Inlet and Mollymook Beach to gain an understanding of the behaviour of the nourishment material. It was recommended that these nourishment areas should be surveyed annually for 3 years post nourishment.

The REF also recommended that photographic monitoring be undertaken of all nourishment areas.

This monitoring is being undertaken by Council. A copy of the REF can be viewed on Council’s website.

https://shoalhaven.nsw.gov.au/LinkClick.aspx?fileticket=2SA6vO8kPYQ%3d&portalid=3

Scientific Indicators for Assessing Dredging Impacts

In order to undertake additional monitoring, quantitative data would need to have need been collected pre and post dredging works. This would provide the ability to analyse pre and post conditions to enable any meaningful analysis of changes in estuary health as a result of dredging.

The commonly used scientific indicators for analysing the health of intermittently closed and opened lakes and lagoons (ICOLLS) on the NSW Coast are tidal regimes, channel morphology, water quality, estuarine vegetation health, marine species numbers and habitat health and benthic macroinvertebrate population health.

It must be noted that there are many factors that influence or affect estuary health, including the indicators above. Careful selection of indicators is necessary to ensure that meaningful data is collected and that it is the actual impact of dredging that is being monitored rather than just general estuary health.

Below is a discussion of potential indicators that could be used to monitor estuary health as part of a dredging project.

Potential Indicators

Tidal Regime – Although the aim of dredging works is not to create or prolong the opening of the estuaries, data on the changes in the range of tidal variation in the estuaries yearly tidal planes, the average water levels and the tidal prisms could be used to analyse any tidal changes and water levels prior to and post dredging. Other variables that would affect this data, include the condition of the estuary entrance and or any artificial openings.

Is this data available? Water level and tidal data is available via the gauges located within Sussex Inlet and Lake Conjola.

Estuary channel morphology – Large scale dredging can change estuary channel morphology (depth & width) which may affect tidal velocities and in turn change the pattern and dimensions of shoaling and scouring in estuary entrances. Useful data collected on channel morphology can show specific areas where scouring or accretion has occurred pre and post dredging. The use of hydro-surveys is one method that can be used to assess channel morphology, as well as analysis of aerial photographic data and digital satellite.

Is this data available? Council undertook hydro-surveys of the actual dredge sites during dredging and after works were completed. Aerial photography is readily available and fairly easy to assess, however, the use of digital satellite data is not available and is relatively expensive.

Water quality – The collection of water quality data is one of the key indicators used to assess the health of estuaries.

Turbidity levels were monitored during the actual dredging works. Turbidity levels are a useful indicator to use to assess water quality effects of dredging due to the disturbance of sediments. Other water quality data that could be collected pre and post dredging works to assess likely impacts, include dissolved oxygen levels, nitrogen (TN), temperature, salinity and phosphorous (TP). Although in order to get any meaningful data that would show any impacts of dredging on water quality for pre and post dredging, the testing would need to be undertaken within close proximity to the dredging location. As turbidity levels remained within REF trigger levels no additional water quality monitoring was undertaken.

Is this data available? – As part of Council’s water quality data monitoring program, samples are collected and analysed for Lake Conjola, Sussex Inlet and Currambene Creek. Water quality tests include temperature, dissolved oxygen, faecal coliforms (CFU/100ml), enterococci (cfu/100ml), phosphorus (mg/L) and total nitrogen (mg/L). This data is available for pre and post dredging, however the water quality test sites are located between 300 metres to 500 metres from the dredge sites and therefore an indicator of general estuary health not dredging. Results of Council’s water quality monitoring program can be found on Council’s AquaData website at https://www.shoalhaven.nsw.gov.au/Environment/Aqua-Data

Estuarine vegetation health – To assess the ecological impacts on estuarine vegetation from any dredging activities accurately, the vegetation communities need to be mapped and their condition assessed. The vegetation communities including seagrasses, saltmarsh, mangroves and swamp oak forest (casuarina) can be impacted by changes in water level, velocities and quality. Pre and post monitoring of the health and condition of these estuarine vegetation communities in locations that could be affected by a dredging project should be undertaken in order to quantify changes in vegetation health.

Is this data available? There is broad scale mapping available of vegetation types for each of the estuaries. As part of the Shoalhaven Dredging REF individual threatened species and threatened ecological communities were identified and assessed. The dredging works were designed to avoid direct impact on estuarine vegetation.

Marine species populations – Some marine fish species utilise estuaries for short periods of time, at a specific period of their life cycle whilst others spend longer periods of time within estuaries. It has been estimated that 60% by weight of the NSW commercial fish catch consisted of species that are dependent on estuaries at some stage of their life cycle (Edgar 2001).

The use of fish and prawn population health to estimate the health of estuaries is difficult and problematic. As different species benefit or increase in estuaries that are in a closed state whilst others may not be tolerant of a closed entrance conditions. Jones and West (2005) in their study of seagrass fish communities in six NSW South Coast ICOLL’s, found that artificially opening the entrance of Lake Conjola to alleviate flooding resulted in the loss of large seagrass beds and subsequent decline in recruitment of economically important fish species to that area.

Their research indicated that artificial openings of lakes or carrying out entrance works, should be done with great caution as the impact of these activities on fish communities remains largely unpredictable (Jones & West 2005).

What data is available? – The NSW Department of Primary Industries - Fisheries may have data on fish populations.

Benthic macroinvertebrates populations – The abundance and diversity of macroinvertebrates is often used as an indicator to assess the condition and health of an estuary, river or stream.

In order to undertake any scientific analysis using this indicator, detailed sample surveys of population within the estuary at each dredging location and control sites would need to be collected pre and post dredging activities to be able to quantitatively assess potential impacts, if any on the population.

What data is available? – Nil

Conclusion

In conclusion, further scientific analysis of the 2016 dredging works, other than the monitoring that has already been carried out, is not feasible for the additional indicators discussed above, because baseline conditions were not collected before the commencement of the dredging. The aim of the dredging REF was to avoid direct impacts and included other mitigation measures.

There is reliable water quality data available to analyse the changes in estuary health pre and post dredging operations. However, this data is limited by the location of Council’s existing water quality testing sites and would only provide information about general estuary health and not changes in estuary health as a result of dredging. Water quality monitoring, in accordance with NSW Environment Protection Authority (EPA) requirements, for turbidity was carried out during dredging operations. Turbidity remained within acceptable levels.

There is also reliable data available to assess tidal regimes. However, given the smaller scale of the dredging works, and the that fact that dredging had minimal influence on the estuary openings, this indicator is unlikely to identify changes to estuary health as a result of the dredging.

Future monitoring programs could be designed and implemented in collaboration with a research institution such as the University of Wollongong. To address the request by the Committee for “scientific analysis of the dredging”, any future monitoring and evaluation program could consider the collection of pre and post dredging data using the following scientific indicators:

· Tidal regimes

· Channel morphology

· Water quality

· Estuarine vegetation distribution and health

· Marine species population health and benthic macroinvertebrate population health

Financial Implications

Any scientific analysis and collection of data for the purposes of assessing changes to the health of estuaries as a result of dredging activities will require additional resources and financial input. Therefore, a monitoring and evaluation program needs to be included as part of the overall project. There is opportunity to partner with research organisations and seek funding for monitoring.

Risk Implications

The risk implications for not undertaking any scientific analysis of the dredging programs/works nominated in this report are, at this time, minimal. Works have been completed and no direct adverse impacts detected nor any indication of adverse indirect impacts. It is relevant however, to consider additional environmental monitoring associated with future dredging operations, depending on the scale of the proposal, longevity and identified environmental concerns in the particular area.

Addendum Agenda - Shoalhaven Natural Resource & Floodplain Management Committee – Wednesday 18 April 2018

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SN18.11 Proposed Millards Creek and Currarong Creek Flood Study Projects

HPERM Ref: D18/68633

Group: Planning Environment & Development Group

Section: Environmental Services

Purpose / Summary

To inform the Committee and Council of the success in receiving grant funding from NSW Office of Environment and Heritage (OEH) for the Millards Creek Flood Study and Currarong Creek Flood Study.

Recommendation

The Committee recommends that Council:

1. Accept the OEH grant of $88,666 toward the cost of the flood study for Millards Creek;

2. Council allocate $44,333 from the 2017/18 Flood Programme budget (Job Number 15706) as Council’s contribution to the Millards Creek Flood Study;

3. Accept the OEH grant of $77,000 toward the cost of the flood study for Currarong Creek; and

4. Council allocate $38,500 from the 2017/18 Flood Programme budget (Job Number 15706) as Council’s contribution to the Currarong Creek Flood Study;

Options

1. As recommended

Implications: Funding for the Millards Creek Flood Study of $88,666.67 and Currarong Creek Flood Study of $77,000.00 have been provided under the NSW State Government ‘Floodplain Management Program’ on a 2:1 basis. Council’s contribution of $44,333 for Millards Creek and $38,500 for Currarong Creek comes from the existing Floodplain Program budget.

2. The Committee could choose to provide an alternative recommendation for future consideration by Council.

Implications: Unknown

Background

Both projects are the first stage of the Floodplain Management process, where Council and the community are seeking to identify the flooding problem of Millards Creek and Currarong Creek, and its tributaries.

Preparation of the technical brief for the flood studies has commenced. The next step will be to seek quotations from suitably qualified consultants via a tender process.

Proposed Millards Creek Flood Study

Millards Creek is located within the Milton-Ulladulla urban area. The watercourse starts from Slaughterhouse Road Milton and discharges into Ulladulla Harbour. There is a history of overland flooding effecting residential properties within the Millards Creek catchment. A number of site specific studies exist, however, they do not capture the catchment holistically. The proposed flood study, will not only look at Millards Creek and its unnamed tributaries but will also consider overland flows. The information available about this catchment is minimal and thus the flood study would give Council better intelligence.

Proposed Currarong Creek Flood Study

Currarong Creek originates from the highlands of Beecroft Peninsula, flows through the Currarong Township and discharges to the Tasman Sea. Black Caves Creek joins Currarong Creek near the Currarong Road Bridge, and the combined flow discharges to the ocean.

Currarong is famous for its tourist attractions such as Abrahams Bosom Reserve and Point Perpendicular Lighthouse and lookout. No site-specific flood studies exist and the current information available about this catchment is minimal. The flood study would give Council better intelligence for both development controls and flood response.

Community Engagement

Advancing Council’s long-term floodplain management program ensures that economic, social and environmental factors relating to the management of floodplains within the Shoalhaven are considered, documented and implemented in Council’s planning programs and policies.

The community will be engaged throughout the duration of the project. Typically, a flood study project includes an initial mail-out and notifications via electronic media to inform residents and ratepayers within the flood study area. Community meetings and drop in sessions would typically be conducted throughout the project. In addition to this, the Shoalhaven Natural Resources and Floodplain Management Committee would be consulted throughout the duration of the project.

Financial Implications

Funding for the Millards Creek Flood Study of $88,666.67 and Currarong Creek Flood Study of $77,000.00 have been provided under the NSW State Government ‘Floodplain Management Program’ on a 2:1 basis. Council’s contribution of $44,333 for Millards Creek and $38,500 for Currarong Creek comes from the existing Floodplain Program budget.

The project is for the provision of consultancy works and will not have any direct or immediate implications on Council’s assets.

The tendering and studies will be undertaken by consultants who will be managed by the Natural Resources and Floodplain Unit of Council.

Risk Implications

No risk implications are applicable if Council undertakes both studies. Council will gain valuable information about the flood behaviour for both catchments, which will inform future land use planning and flood emergency management processes.

Council has a statutory responsibility for land use planning and management under the Environmental Planning and Assessment Act. If Council decides not to undertake these studies, the risk may be poor land use planning and emergency management for these areas. In addition, obligations under the Floodplain Development Manual (2005) will not be met.