North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
1 Introduction 1.1 I undertook a peer review of the Surface water technical report for the North East Link (Project). This peer review report is contained in Technical Report P - Surface Water in the Environmental Effects Statement (Technical Report) at Appendix G and is dated 4 March 2019 (Peer Review Report). 1.2 I have been instructed by Clayton Utz on behalf of NELP to review and respond to the public submissions and give evidence on the environmental effects of the Project relevant to my area of expertise.
2 Qualifications and experience 2.1 Annexure A contains a statement setting out my qualifications and experience, and the other matters raised by Planning Panels Victoria’s Guide to Expert Evidence. A copy of my curriculum vitae is provided as Annexure B.
3 Peer Review 3.1 As Peer Reviewer I was engaged during the preparation of the EES to review water quality, geomorphology and flood estimation methodologies and conclusions as presented in the Surface Water technical report. This included the assessment of the pre- to post- project changes in flooding, but not the engineering designs – a subject that I am familiar with but is outside my specific areas of expertise. 3.2 I engaged in discussions with technical personnel who had contributed to the report regarding the assumptions made, the conclusions reached, the approaches taken, and the standards, data and calibration methods used. 3.3 A number of versions of the draft surface water report were provided for review during the course of the development of the EES. The authors addressed peer review comments on the reports during each round of this process. 3.4 I adopt the Peer Review Report, in combination with this statement, as my written expert evidence for the purposes of the North East Link Inquiry and Advisory Committee’s inquiry into the environmental effects of the Project.
4 Further work since preparation of the Peer Review Report 4.1 Since the Peer Review Report was finalised, I have undertaken further review of a Technical Memorandum titled ARR 2016 Sensitivity Assessment – Watsonia Station drain, Banyule Creek and Koonung Creek models dated 15 July 2019. This Memorandum is included in Annex C to this report. 4.2 A summary of my findings in relation to this further work is: • Unsurprisingly, the application of the latest national guidelines for flood estimation provided in Australian Rainfall and Runoff (ARR) 2019 compared with ARR 1987 led to some differences in the estimates of pre-development flood level depths, velocities and extents. • In some cases pre-development flood depths estimated using ARR 2019 are less than those estimated using ARR 1987. In some cases the opposite is true.
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
• It is noted by the authors that the application of a constant “continuing loss rate” (a hydrological model parameter) as recommended in ARR 2019 compared with reducing continuing loss rates recommended in ARR 1987 results in lower extreme flood estimates than the earlier guidelines. This is despite an increase in rainfall intensity compared with the earlier guidelines. • In most cases the differences in modelled flood levels, extents and velocities are not substantial between the two methodologies and are within the level of modelling accuracy. • The models are constrained by the lack of observed local data. Consequently recommended default parameters are utilised to generate model results. These default parameters have been developed based on experience in the modelling of flood inundation over many studies in urban areas so they provide a level of confidence that the comparison between pre- development and post-development change is appropriate. • However, the absolute modelled water levels are subject to error in which case engineers should take this into account and adopt appropriate freeboard in their engineering designs. • At a few locations there are substantial differences in pre-development modelled flood levels between the two methodologies. These locations appear to be near model boundaries or near significant flow constraints such as existing embankments, underpasses or culverts. The authors of the Technical Memorandum suggest that these anomalous results are generally due to modelling assumptions (e.g. boundary conditions). • It is important to note that Melbourne Water Corporation has now adopted ARR 2019 as its standard methodology for the assessment of pre-development to post-development changes in flooding. Substantive changes in flood inundation or frequency are not permitted as recognised in EPR SW6. • As a consequence, it is my understanding that project approval will be dependent on the adoption of EPR SW6 that required amelioration of any substantive change in pre- development to post-development flood risk based on the final configuration and design of the North East Link. • The results presented in the Technical Memorandum do not alter the types of infrastructure, design constraints or conditions required for amelioration of changes in flooding. • However, the results do indicate that significant care is required to examine, and where possible confirm, some the localised flooding as part of detailed design. Where necessary, appropriate additional freeboard should be incorporated in the detailed design to account for uncertainty. 4.3 Since the Peer Review Report was finalised, I have also been requested to read the EES and consider the potential implications of changes in hydrology and water quality on the environment and any other matters that I consider that I could reasonably comment upon. 4.4 This further work has not caused me to materially change my opinions as expressed in the Peer Review Report.
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
5 Summary of key issues, opinions and recommendations Key issues identified in this Statement are:
• A need for more detailed information regarding the design of the works and mitigation of flood risk. • Potential flood impacts on private property or existing infrastructure • Safety and operation of the southern portal design • Integrated water management and Water Sensitive Urban Design (WSUD) • Water quality impacts during construction
I am satisfied that the EPRs are sufficient to account for each of these matters.
Submissions on minor proposed amendments to the EPRs appear appropriate as they seek to clarify the intent and/or involvement of regulators and other relevant parties; or seek to extend monitoring of Project performance to operations.
6 Submissions Submissions received 6.1 I have read the public submissions to the EES, draft planning scheme amendment and works approval application and identified those that are relevant to the Technical Report and my area of expertise. These include the following submissions: 25, 40, 47, 82, 88, 100, 112, 113, 145, 208, 237, 274, 290, 312, 316, 340, 375, 396, 411, 415, 446, 512, 514, 516, 519, 520, 522, 526, 533, 534, 539, 552, 556, 563, 598, 600, 601, 611, 617, 634, 645, 646, 657, 666, 669, 694, 700, 703, 714, 715, 716, 717, 725, 742, 774, 777, 783, 793, 800, 802, 803, 820, 826, 848, 857 Summary of issues raised 6.2 The submissions have raised the following issues relevant to my area of expertise: a) Additional information required on the detail of flood modelling results or approaches b) Potential flood impacts of the Project on private property c) Amelioration of existing stormwater flooding of properties (Bulleen & Banyule Creek) d) Impacts on local flooding arising from changes to existing retarding basins or other infrastructure e) The need to account for impacts on significant water infrastructure including stormwater, sewerage and recycled water assets and functionality. f) The safety and operation of the southern tunnel portal in the floodplain g) The need for integrated water management planning and Water Sensitive Urban Design h) Increased stormwater runoff and associated water quality impacts i) Lack of information on changes in local hydrology and consequent impacts on aquatic ecosystems including wetlands j) The impacts of isolating the Banyule Creek headwaters k) Impacts on Koonung Creek and other waterways l) The potential for water quality impacts during construction
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
In addition to the Peer Review process I have read relevant sections of the EES and am answering questions to the best of my ability. Most of my responses are submitted as comments regarding ways in which the issues raised might be addressed recognising that in my opinion the EPRs are generally sufficient to accommodate effective design decisions to ameliorate flood impacts provided they are appropriately implemented and monitored. I also recognise that there is on-going involvement of regulatory and approvals agencies such as Melbourne Water and Vic EPA on many of these matters; and there are future stages of more detailed engineering design planned for the Project. Response to issues raised 6.3 Set out below are my comments and responses to the issues raised by the written submissions relevant to the area of my expertise. 6.4 Additional information required on the detail of flood modelling results or approaches [Issue a)]. The City of Manningham has raised the need for involvement and scrutiny of hydraulic modelling results to ensure effective integration of local stormwater infrastructure and consideration of local flood impacts in line with the proposed Project. Similar concerns regarding the detail of the current design are expressed by other nearby local government agencies. It is important to note that in the Port Phillip and Westernport region, Melbourne Water is accountable for managing urban stormwater flooding in catchments greater than 60 hectares, with Local Government accountable for catchments of less than 60 hectares. During the review process I raised the issue of approval for flood impacts and was provided with evidence that there was on-going and active engagement with Melbourne Water in this regard, not least related to changes in design standards associated with Australian Rainfall and Runoff. I was also advised of engagement with local government agencies and noted the engagements in Table 5.3 of EES Technical Report P Surface water p. 63 along with the use of local government flood modelling results in the analysis. As part of their EES submissions there is also evidence of a level of engagement by the North East Link Project with Local Government, Melbourne Water and Vic EPA. During the peer review process it was evident that the Reference Project is not a detailed design and there are additional stages of design to follow. My understanding is the Reference Project is an initial design to test the environmental effects and the adequacy of the EPRs. The results of the modelling along with EPRs were in my opinion sufficient to demonstrate that the flood impacts arising from the development could be managed in consultation with approving authorities during the more detailed design stage(s). In many localities the modelling suggests that this design process is likely to ameliorate flood impacts to very close to current conditions. However, in some local instances it may not be possible within the constraints of the footprint or available design options to have zero impact on existing flood levels. In these instances a risk based design approach should be used to minimise the risks to public safety or property in a way that is satisfactory for approval.
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
In my opinion it would be sensible to closely liaise with Local Government and Melbourne Water during the detailed design stages to ensure appropriate sharing of information and adoption of design elements that meet flood management requirements at the appropriate spatial scale. This is contemplated in the existing surface water EPRs particularly SW6, SW8, SW12. The EES submissions have highlighted the desire by Melbourne Water and Local Government agencies to work closely with the Project to ensure any impacts on existing flood levels, flood storage and other factors are appropriately modelled and ameliorated. 6.5 Potential flood impact of the Project on private property [Issues b) and c)] There was a general concern expressed in community submissions regarding the localised impacts of the Project particularly where there are interfaces with local government infrastructure for stormwater management at Bulleen and in Banyule Creek. However, respondents often did not refer to changes in flooding as estimated from modelling work presented in the EES Technical Report P or Technical appendix C. Instead they relied on their knowledge of current flood levels and frequency to describe flood hazards, or they expressed a broad concern about flooding and its effects on local residences and/or infrastructure. It is important to note that in the Port Phillip and Westernport region, Melbourne Water is accountable for managing urban stormwater flooding in catchments greater than 60 hectares, with Local Government accountable for catchments of less than 60 hectares. During the review process I raised the issue of approval of flood impacts and was provided with evidence that there was on-going and active engagement with Melbourne Water in this regard, not least related to changes in design standards associated with Australian Rainfall and Runoff. It was also evident that: • Modelling results from smaller local government catchments were being integrated into the assessment (e.g. EES Technical Report P Surface water Section 5.3.2, first paragraph, p.37; Section 5.3.3, first paragraph, p.39; and Section 5.3.4, first paragraph, p.41) • There was engagement with local government agencies and Melbourne Water during the development of the EES (EES Technical Report P Surface water Table 5-3, p. 63) • There is an intention to engage with local government during concept and detailed design (e.g. EES Technical Report P Surface water p.120-121; EES Technical Report P Surface water p.137, p.176, p.180), and • The reference design is a preliminary design (i.e. subject to further design stage(s)). The results of the modelling along with the adopted EPRs were in my opinion sufficient to demonstrate that the flood impacts arising from the development could be managed in consultation with relevant authorities during more detailed design stage(s). Specifically EPR B3 requires minimising and remedying damage or impacts on third party property and infrastructure; SW6 requires the Project to minimise the risk from changes to flood levels, flows and velocities; and SW7 requires flood emergency management plans to be developed. In my opinion it would be sensible to closely liaise with Local Government and Melbourne
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
Water during the detailed design to ensure appropriate sharing of information and adoption of design elements that meet requirements at these two spatial scales. Where there is a very close interface between the Project and existing stormwater infrastructure (e.g. retarding basins) then opportunities should be sought to at least preserve, or ideally ameliorate, existing stormwater flooding where possible. On-going interaction with Melbourne Water and Local Government agencies is recommended to ensure changes in flooding are minimised during the more detailed design phase(s). This is contemplated in the existing surface water EPRs particularly SW6, SW8, SW12. 6.6 Potential flood impact of the Project on existing infrastructure [Issues d) and e)] A range of existing infrastructure (e.g. retarding basins, pump stations, pipelines) exists within the footprint or influence of the project. The current Environmental Performance Measures including B3, B5, SW6, SW7, SW10, SW11, SW12, LP1, LP2 and LP3 recognise the need to protect existing infrastructure and amenity. Where there is a very close interface between the Project and existing stormwater infrastructure (e.g. retarding basins) then opportunities should be sought to at least preserve, or ideally ameliorate, existing stormwater flooding where possible. Designers will also need to work closely with water and sewerage utilities and other infrastructure owners to ensure existing functionality is preserved or replaced. On-going interaction with Melbourne Water and Local Government agencies is recommended to ensure changes in flooding are minimised during the more detailed design phase(s). 6.7 The safety and operation of the southern tunnel portal in the floodplain [Issue f)] There was some concern expressed regarding the safety and utility of the location of the southern tunnel portal in the floodplain. EES Chapter 24-Surface water p.24-44 notes the intention to use passive measures such as flood walls and road embankments (geometry) as well as active measures such as flood gates to provide protection under large flood events. A flood wall is typically an engineered structure such as a concrete, masonry, glass or sheet pile wall that provides a barrier to flood waters. Effectively a flood wall is a levee, though the latter term is usually reserved for earthen embankments. There are a number of examples from around the world where flood gates and traffic management are effectively managed under similar circumstances. A real-time flood warning system similar to the Kuala Lumpur Smart Tunnel project could be appropriate to support safe operation of the flood gates. In this system real-time rainfall and river level data is used to predict flooding via a hydrological model with results then passed to a hydraulic model that includes operations and supports operator decisions on flood management via a dashboard arrangement. Consistent with EPR SW7 a risk management plan should be developed to ameliorate the risks of tunnel portal inundation as part of detailed design.
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
Based on Submission 600 from EPA Victoria, it is clear that there are also some potential environmental issues that need to be carefully considered during detailed design and incorporated into a consolidated plan for the portal and appurtenant infrastructure. 6.8 Integrated Water Management and Water Sensitive Urban Design [Issues g), h), i), j) and k)] There is widespread and strong consensus in respondents’ submissions that there is a need to carefully design an integrated water management system that captures, stores and slows down the release of additional volumes of stormwater runoff that would be generated by the Project. Careful consideration of water quality amelioration is required as part of this planning process. Many submissions also refer to the need to preserve environmental, amenity and other values as part of an Integrated Water Management Plan for the Project. The key principles of WSUD from a stormwater management and planning perspective are (https://www.clearwatervic.com.au/user-data/resource-files/Water_Sensitive_Urban_Design.pdf):
• Protect natural systems – protect and enhance natural water systems (creeks, rivers, wetlands) within urban developments • Protect water quality – improve the quality of water draining from urban developments into creeks, rivers and bay environments • Integrate stormwater treatment into the landscape – use stormwater treatment systems in the landscape by incorporating multiple uses that will provide multiple benefits, such as water quality treatment, wildlife habitat, public open space, recreational and visual amenity for the community • Reduce runoff and peak flows – reduce peak flows from urban development by on site temporary storage measures (with potential for reuse) and minimise impervious areas • Add value while minimising development costs – minimise the drainage infrastructure cost of development • Reduce potable water demand – use stormwater as a resource through capture and reuse for non-potable purposes (e.g. toilet flushing, garden irrigation, laundry).
The Environmental Performance Requirements in the EES recognise the need to incorporate WSURD (Water Sensitive Urban and Road Design) via SW11 and indirectly via a number of other EPRs. The following Table maps WSUD principles to EPRs: WSUD Principle Environmental Performance Requirement Protect natural systems SW1, SW8, SW9, SW11, FF4, FF6, FF9 Protect water quality SW1, SW2, SW3, SW4, SW5, SW11, SW14, CL1, CL5, CL6 Integrate stormwater treatment SW11, SW12, LP1, LP2, LP3 into the landscape Reduce runoff and peak flows SW5, SW6, SW11, SW13 Add value while minimising SW11 development costs Reduce potable water demand SW11, SCC5
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North East Link Inquiry and Advisory Committee Expert Witness Statement of David Fuller
By its very nature, WSUD requires a trade-off between development and preservation, design and functionality, mitigation and rehabilitation, and between practicality and the available footprint for works and measures. The key is to undertake a process focussing on the issues and how the need for trade-offs can be avoided where possible. This process is necessarily multi-disciplinary and starts from considering existing conditions, plans, and strategies and the impacts of the proposed development. It is a process that necessarily involves a range of stakeholders. In my opinion the EES does contemplate the development of the Project in terms of WSUD and sensitivity to existing plans, infrastructure and activities. However, this element of the EES is less clear, and the process for implementation is perhaps less transparent, than might otherwise be the case. NOTES ON SOME INDIVIDUAL SUBMISSIONS: Observations from my review of some individual submissions are provided below. My response to these submissions is at the end of this section. Submission 800 by Melbourne Water Corporation (MWC) encapsulates many of the issues that need to be considered by the Project and reflects the integrating nature of water resources management considerations and the expectations of the wider community as expressed under various policies, laws, regulations and plans. Overlaid with community expectations and plans for urban design and use of these areas, integrated water management is a critical issue that the Project needs to explicitly address. MWC highlights the existing strategic context of plans and strategies that are seeking to strike a balance between environmental and developmental pressures along the Yarra River and its influent streams, floodplains and wetlands. With respect to water management, the interaction of surface water and groundwater especially near the Yarra River and supporting billabongs and wetlands is a key feature, as are existing investments in the capture, retention, treatment and reuse of stormwater. MWC notes that the Yarra Strategic Plan incorporates a principle that “ There should be a net gain for the environment in the area of the Yarra River land arising out of any individual action or policy that has an environmental impact on Yarra River land” . They further propose a range of mitigation measures to better align the Project with the Yarra River Protection (Willip-gin Birrarung Murron) Act 2017 on page 6 of their submission. Of particular note are the following MWC mitigation recommendations related to water:
• “Design guidelines should be agreed for this area to ensure a high quality built and landscape design, and the integration of environmental objectives to contribute to biodiversity and integrated water management.” • “Provide a generous setback at the river’s edge for revegetation and access.” • “… It is essential that replacement parkland is developed in accordance with Yarra River protection principles that seek to prioritise environmental benefits to the river.” • “Impact on key priority billabongs within the Yarra floodplain must be avoided.”
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MWC also notes their implementation of:
• An Urban Cooling Program that promotes (amongst other things) “Vegetation and water used to cool green space can also provide habitat, improve amenity, and help manage stormwater flows to waterways.” • A Healthy Waterways Strategy that has led to the development of “catchment-specific visions, goals, long-term targets … and 10 year performance objectives” that “contribute to the best waterway outcomes for effort and investment …” . The Yarra Catchment Program that has been developed to deliver “ ecological health and value to the community continuously improved through rehabilitated waterways and balanced uses.” It includes specific outcomes nominated for a number of sub- catchments and billabongs including Yarra catchment, Koonung Creek sub- catchment, Yarra River Lower sub-catchment, Annulus Billabong at Yarra Flats, Banyule Flats Billabong and Bolin Bolin Billabong. . MWC has also suggested some “minor amendments” to EPRs that are discussed later in this Witness Statement. Submission 600 from EPA Victoria notes that New EP Act will have “material implications for the Project including by introducing a new permissions (licence) regime, a general environmental duty and new duties in relation to the management of contamination” . The EPA considers the Project “ has established appropriate EPRs to manage and mitigate potential environmental effects” though a range of minor amendments are recommended as discussed later in this Witness Statement. Some other water-related aspects of EPA Victoria’s submission include:
• The extension of monitoring to cover pre-construction (baseline), construction and post-construction periods • Recognition of the complexity of WSUD designs and performance requirements and the need for an External Auditor • The need to work towards improved outcomes for Banyule Flats and Bolin Bolin billabongs • A willingness for on-going involvement with the Project during further design stages
Submission 774 from Parks Victoria notes there are potential opportunities from the Project for enhancement of the environmental and cultural water flows at Bolin Bolin Billabong. Presumably this is expected to be via appropriate management of stormwater and infiltration augmenting the groundwater regime or via artificial watering events post remediation of water quality issues. Parks desire careful consideration of access to parkland with the impacts of infrastructure on the values of the reserve to be “well considered, planned for and managed”. This includes the location of WSUD subsurface storage and bioretention facilities within or in close proximity to the Parks Victoria Estate. Submission 742 from Birrarung Council suggests that the North East Link Project “ has a unique opportunity to deliver a net benefit, by taking a whole of corridor approach”. With respect to water matters this is related to improved management of stormwater and
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stormwater quality; but also to the concept of managing “the river and its parklands, as a single living and integrated natural entity ”. The Council is concerned that the scope of the EES will be too narrowly focussed on minimising impact rather than seeking to deliver the Yarra River 50-year Community Visions and the Wurrundjeri Water Policy. Submission 716 on behalf of the Banyule, Boroondara and Whitehorse City Councils raises a range of water-related issues including:
• Concerns regarding the ecological integrity of the Yarra River Floodplain, the Bolin Bolin wetlands and Koonung Creek. • Ground and surface water impacts including impacts on ecology and the limits of available information on the connectivity of these resources. • Concerns regarding the under-grounding of creeks and the consequences of this particularly Banyule Creek, Koonung Creek • Loss of open space to accommodate stormwater infrastructure. • Inadequate assessment of drainage works on wetlands and parks • Lack of detail on how SEPP (Waters of Victoria) would be applied at key locations • Uncertainty regarding some WSUD and flood retention elements (e.g. Borlase Reserve, Elgar Park, Eram Park) • Consideration of climate change on hydrological regimes • The EES does not demonstrate WSUD for the entirety of the Project • The opportunity to treat the Project as an Integrated Water Management precinct to realise strategic precinct wide goals as a national benchmark for major road projects.
Submission 316 from Manningham City Council raises a range of water-related issues including:
• Loss of open space that forms part of the Bolin Bolin Integrated Water Harvesting Facility completed in 2017. • Impacts of the reference design on Koonung Creek corridor. • Concerns regarding the under-grounding of Koonung Creek and its consequences • Potential impacts on Bolin Bolin Billabong
RESPONSE TO SUBMISSIONS: The current EPRs point to on-going engagement with regulators and approval authorities as design progresses and more detail becomes available. It is clear from MWC and Vic EPA submissions that more information will be required to support consideration of pertinent matters. Under this process it is expected that consideration will be given to each element of the Project and its beneficial or detrimental impacts on multiple aspects of the catchment environments. These include urban design, landscape and visual amenity; social, cultural and recreational value; groundwater impacts; surface water impacts – particularly flood risks and stormwater management; groundwater – surface water interactions; and impacts on billabongs and groundwater dependent ecosystems.
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An example of this is decisions on the appropriate management of wetland systems such as Bolin Bolin Billabong. In their response, MWC describe the need to develop specific designs for the rehabilitation of billabong and wetland systems taking into account significant changes in groundwater and surface water hydrology that have already occurred as well as the practical issues in developing engineering solutions. It is also my experience in environmental watering projects that specific designs are required. It is recognised that the Bolin Bolin Billabong has been affected by past changes in flow regimes, stormwater runoff, and other matters. The Project’s current groundwater modelling indicates a likely reduction in groundwater levels and yet the groundwater at the billabong is known to be connected to Yarra River levels. Vegetation around the wetland is also likely to be dependent on groundwater levels at the billabong, and it is known that Melbourne Water has completed some artificial watering in recent times possibly in connection with the Bolin Bolin Integrated Water Management Project. The management of the billabong is therefore dependent on understanding the interactions at a local scale of groundwater, surface water, vegetation, stormwater (quality and quantity) and their connections. Importantly the Project not only reduces groundwater levels, but increases stormwater runoff. Consequently there is an opportunity through careful and integrated design to try to achieve multiple outcomes – i.e. mitigate groundwater impacts by direct or indirect infiltration of stormwater, improve the health of the wetland and its vegetation, reduce the amount of stormwater that needs to be managed in some other way. The potential for win:win outcomes is recognised in the Parks Victoria submission. To address this effectively a multidisciplinary team needs to come together to assess the full hydrological cycle. The under-grounding of creeks is a key topic raised by some respondents. In the case of Koonung Creek which is in part already “under-grounded”, there is an existing discontinuity in the waterway that would have some ecological effect. It is understood that the footprint for development is very tight and efforts have been made to formulate engineering solutions in accordance with WSUD principles. The EPRs require ongoing interaction with relevant Local Government agencies and others to maximise the utility and minimise the environmental impact of the Project in this area. Similarly for Banyule Creek there is some opposition to under-grounding and various detailed design options need to be considered to minimise the impacts of doing this. The need for on-going consultation is recognised in EPRs SW4, SW6 and SW8. In my view, resolution of matters such as those outlined above will require integrated planning and assessment of both groundwater and surface water management along the whole alignment. This would naturally be a part of the development of an approved Water Sensitive Urban Design (SW11) along with consideration of aquatic habitat protection (FF4), minimising land use impacts (LP1) and other EPRs. 6.9 Water quality impacts during construction [Issue l)] Water quality risks during construction are adequately identified in the EES although the assessment remains qualitative rather than quantitative. Mitigation measures are heavily
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focussed on management of construction impacts through bunding of chemicals and fuels, scheduling of works, the use of standard construction guidelines and measures (EPRs CL1, CL5, CL6, SW1, SW2, SW3, SW4, SW5, SW9, SW11 and SW14). In my view these are adequate and normal measures that would be used to mitigated water quality impacts during construction along with regular monitoring of works, measures and water quality parameters. It was expected that the monitoring programs would be approved and overseen by regulators and this is clearly the intention in some of the responses from Melbourne Water and EPA Victoria.
7 Environmental Performance Requirements 7.1 It is my view that the Environmental Performance Requirements relevant to my area of expertise, being EPRs SW1, SW2, SW3, SW4, SW5, SW6, SW7, SW8, SW9, SW10, SW11, SW12, SW13, SW14, B3 and CL5 are appropriate and will ensure that the environmental effects of the Project relevant to my area of expertise can be suitably managed to achieve acceptable outcomes. 7.2 In addition, Environmental Performance Requirements B5, CL1, CL5 & CL6, FF4, FF6, FF9, GW1, GW2, LP1, LP2, and LP3 provide for the protection of existing utility assets, management of spoil and maintenance of ground cover, management of hazardous chemicals, and other aspects of relevance to surface water and flood management. It is expected that these additional EPRs will complement and reinforce the surface water specific EPRs. 7.3 I note that Melbourne Water has provide some general comments on EPRs and has sought amendments to the following surface water EPRs:
• EPR SW6: MWC recommends minor changes to the wording to reflect its role and the incorporation of its latest flood guidelines viz. Standards for Infrastructure Project in Flood-Prone Areas (2019). Comment: I generally agree with this amendment.
• EPR SW11: Is not considered sufficient to maintain or improve the hydrology of waterways. Instead MWC recommends a more specific approach including targets based on maintaining natural water quality and flow regime. Comment: It is expected that SW11 would be implemented as part of a process of developing an Integrated Water Management Plan for the Project. This Plan should set performance targets as suggested by Melbourne Water (and Vic EPA).
• New EPR SW??: MWC recommend a new EPR (Submission 800 p20) regarding a post- construction stormwater monitoring program to confirm the effectiveness of Water Sensitive Road Design measures and if required, identify and implement contingency measures. Comment: It is expected that this would be developed in conjunction with the detailed design of the Project. Suitable monitoring programs need to be designed to support both a statistical and a functional assessment of performance against pre-established standards.
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• EPR SW8: MWC recommends offsets are established in accordance with the Urban Design Strategy for impacts from waterway modifications. Comment: I cannot comment on the appropriateness of offsets or whether the UDS is the right vehicle for this. 7.4 I note that Vic EPA has sought an amendment to the following surface water EPRs relevant to water:
• EPR SW4: EPA recommends some minor changes to this EPR including monitoring of surface waters at multiple locations for three (3) years after commencement of North East Link operations to confirm the effectiveness of environmental controls. They also recommend a change in the reference to Best Practice Guidelines for Urban Stormwater Comment: I agree with these recommendations but note that spot sampling of water quality would generally be insufficient to provide clarity in the performance of WSUD elements. The monitoring program should seek to assess the performance of WSUD elements via the combined use of continuous and spot sampling and integrated water quantity and quality modelling.
• EPR SW5: EPA recommends that they be consulted in the development of the Surface Water Management Plan for construction. They also recommend “ monitoring and evaluation of the effectiveness of Water Sensitive Urban and Road Design in protecting receiving waters” ; and a change in the reference to best practice sediment and erosion control and monitoring. 7.5 Apart from my comments on the proposed amendments to the EPRs by Melbourne Water and EPA Victoria, I do not recommend any changes to the environmental performance requirements for the Project.
8 Declaration 8.1 I have made all the inquiries that I believe are desirable and appropriate and no matters of significance with I regard as relevant to my knowledge been withheld from the North East Link Inquiry and Advisory Committee.
Signed Date: 15 July 2019
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Annexure A – Matters Raised by PPV Guide to Expert Evidence
a) The name and address of the expert
David Allan Fuller Principal Water Management & Technology Hydro-electric Corporation t/a Entura 1 Level 25, 500 Collins Street, Melbourne, VIC 3000
b) The expert’s qualifications, experience and area of expertise
I hold the following degrees: • Bachelor of Science (Physics/Mathematics) • Certificate Master’s level post-graduate course in Hydrology, UNSW • Postgraduate Diploma in Statistics • Master of Business Administration • Master of Economics
For the past 37 years I have practiced in engineering hydrology, hydraulics, stream gauging, water quality, environmental hydrology, environmental water requirements, water management and the environmental impacts of developments across all states and territories of Australia and internationally.
I have worked in private firms as a consultant, for a major hydro-electric utility, and for a State water and environmental regulatory agency. My clients have included national and international corporations, State authorities, developers, Commonwealth agencies and private companies.
My key areas of expertise are flood hydrology, hydroinformatics, environmental hydrology and hydroeconomics.
c) Details of any other significant contributors to this statement (if any) and their expertise
Nil. The views presented in this report reflect my opinions based upon my independent review of reports, maps and analyses presented.
However, unrelated to this project, I have discussed and continue to discuss and investigate the issues associated with the introduction of the latest version of Australian Rainfall and Runoff (2019) with the expert hydrologists and hydraulic modellers within my team at Entura.
d) All instructions that define the scope of this statement (original and supplementary and whether in writing or verbal)
I was engaged via Entura to undertake the expert peer review of surface water studies to:
i. assess the process, methodology and assessment undertaken in preparation of the Impact Assessment Report including any assessment criteria applied or assumptions relied upon;
1 Entura is the trading name of the consulting division of the Hydro-electric Corporation. Entura provides consultancy services to the Hydro-electric Corporation and to clients across Australia, South Asia and South-East Asia and the Pacific.
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Annexure A – Matters Raised by PPV Guide to Expert Evidence
ii. identify any additional matters which should be considered in order to address the EES Scoping Requirements, "public works" declaration or to otherwise adequately assess the likely impacts of North East Link; iii. assess the adequacy of proposed Environmental Performance Requirements to manage potential adverse impacts arising from North East Link.
The peer review process was limited to a review of reports and discussions with technical personnel who had contributed to the report regarding the assumptions made, the conclusions reached, the approaches taken, the standards used, and the data and calibration methods supporting the modelled results.
No detailed hands-on technical evaluation of the hydraulic or hydrological models was undertaken.
e) Details and qualifications of any person who carried out any tests or experiments upon which the expert relied in preparing this statement.
Nil.
f) Any questions falling outside the expert’s expertise
Some of the issues raised by respondents are at the edges of my experience. For example, water sensitive urban design. However, I believe I have sufficient knowledge of these matters to be able to provide a sensible commentary on the broad issues raised by the respondents.
g) Key assumptions made in preparing the Peer Review Report
Nil
h) Any departures from the findings or opinions expressed in the Peer Review Report and, if so, why
No departures. However, I have added commentary on matters of relevance to surface water management that were raised in the submissions received.
i) Whether the Peer Review Report is incomplete or inaccurate in any respect
I believe the report is accurate and complete based on the information I have to hand.
j) Details of any changed circumstances or assumptions since the Peer Review Report was prepared and whether these affect the opinions expressed in the Peer Review Report.
Nil
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Annexure B – Curriculum Vitae
A short CV is provided below highlighting my qualifications, experience, work history and listing some relevant project work demonstrating relevant experience to this project according to the areas of my expertise.
David Fuller
David is currently Entura’s Principal Water Management & Technology and in this role he leads the organisation’s hydrology, hydraulics, hydrographic, specialist data management services. He has over 35 years of experience in hydrology, water quality, waterway health and sustainable water management planning. An experienced consultant, David has worked both in Australia and overseas for mining companies, private organisations, state and federal government agencies, and power and water utilities. His primary areas of expertise include flood hydrology and hydraulics, water balance modelling, stochastic hydrology and optimisation, water quality assessment and modelling, environmental hydrology, and natural resource economics.
David’s projects often draw on a range of disciplines and present the results in a way that supports clear decision making. David has worked on some of the largest EIS projects in Australia and provided independent expert peer review and evidence to planning panels and tribunals on the hydrological, hydraulic and environmental impacts of developments and water diversions. As a trained economist, David has also provided independent peer review and advice to state and national governments on the economic impacts of prospective investments.
Qualifications
Bachelor of Science (Physics/Mathematics), University of Tasmania, 1982 Certificate Post-graduate Course in Hydrology, University of New South Wales, 1984 Diploma in Statistics, University of New England, 1988 Master of Business Administration, La Trobe University, 2005 Master of Economics, University of New England, 2014
I have also undertaken the following post-graduate residential workshops relevant to my areas of science and engineering practice:
• Stochastic Data Generation Workshop, University of Melbourne, 1989 • Water Quality in Catchment Management Workshop, University of Canberra, 1993
Professional associations
American Geophysical Union Australian Water and Wastewater Association International Association of Hydrological Sciences
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Annexure B – Curriculum Vitae
Employment history and achievements
1982 – 1991 Hydrologist / Principal Hydrologist, Hydro -Electric Commission, Tasmania 1991 – 2002 Manager Water Resource Assessment, Department Primary industries, Water and Environment, Tasmania 2002 – 2014 Senior Principal Consultant, URS Australia Pty Ltd 2014 - 2016 Director, DeepRiver Associates Pty Ltd 2016 - 2019 Princip al Water Management & Technology, Hydro -electric Corporation t/a Entura
Key areas of expertise include:
• Water balance and demand modelling including multiple use reservoir systems, yield estimation and drought management. • Flood hydrology including extreme flood estimation, development of regional estimation procedures, flood frequency analysis and stochastic data generation. • Water quality and ecosystem health monitoring and modelling including environmental flow estimation and ecological risk assessment • Stream gauging and water data collection systems • Hydrological statistics, trend analysis and time series modelling • Hydroinformatics including real-time data management systems • Water allocation systems, management and planning. • Managing trade-offs between resource managers, users, and the environment. • Hydroeconomics & evaluation of water resource investment strategies and programs. • Development and review of water management policies and strategies. • Hydraulic modelling review and assessment
Some relevant project experience includes:
• Subject Matter Expert, Independent Audit of WaterNSW Flood Management and Operations, Ernst and Young, NSW • Independent Expert Reviewer, Surface water impacts, Melbourne Metro Rail Project, Victoria • Project Director, Flood estimation and inundation mapping for numerous projects in Victoria, Tasmania and NSW • Steering Committee Member and Contributor, National Floodplain Management Guidelines, Commonwealth of Australia • Independent Reviewer, Design flood estimation for Warren, South Para, Barossa dams, South Australia • Independent Reviewer, water balance modelling, flood estimation and dam break analysis, Independence Group, Benambra, Victoria • Project Director, Flood estimation, hydraulic modelling and levee design, Latrobe Council • Chair Independent Expert Review, Lower Lachlan Groundwater Sharing Plan, Natural Resources Commission, NSW
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Annexure B – Curriculum Vitae
• Project Director, Dambreak modelling and mapping Glen Maggie Dam, Victoria • Independent Reviewer, Dambreak analysis for Greenvale Dam, Melbourne Water • Independent Reviewer, Engineering, economic and water savings reviews for major irrigation investments DSEWPaC, Canberra • Project Director, Environmental works and measures for Gunbower Forest flood inundation, North East Catchment Authority, Goulburn Murray Water, Murray Darling Basin Authority • Independent Reviewer, Fred Haigh Dam design flood estimation, Sunwater, Queensland • Independent Reviewer, Engineering, economic and water savings reviews for environmental flows projects, Department of Agriculture and Water, Canberra • Project Director, Review of water management and sustainability issues Latrobe Valley, DPI Vic • Chair, State of Environment Report - Inland Waters and Wetlands chapter, SOE Unit • Lead Expert Reviewer, Impact Assessment of Hydro-reregulation of Tasmania’s Rivers, Basslink Project EIS, Department of Primary Industries, Water and Environment, Tasmania • Lead Author, Critical Impacts of Coal Seam Gas and Coal Mining Techniques on the Water Environment, Department of the Environment, Canberra • Project Director, Development of a method for assessment of salinity impacts of environmental works and measures, MDBC • Project Director, Gladstone coal seam gas project surface water studies and management strategy, Santos • Consortium leader, Development of SIMRAT model to assess the salinity impacts of interstate trade in the Murray-Darling Basin, MDBC • Project Director, Great Barrier Reef Pesticide Usage Monitoring System, DEWHA • Project Director, Heavy Metals in the River Murray project, MDBC • Project Director, National Chemical Monitoring Initiative, DEWHA • Expert Reviewer, Water Balance Modelling –Project Nammaldi, Rio Tinto • Expert Reviewer, Development of Water Balance and Sedimentation Models, Confidential Copper Mine, Indonesia • Project Specialist, Development of a World-wide Water Risk Management Tool, The Coca Cola Company, North America • Leader, Independent value engineering review of a proposed water storage in the Mitchell River catchment, Southern Rural Water, Victoria • Expert Peer Reviewer, Confidential Heavy Metals Mitigation Project, Government of Queensland • Independent Peer Reviewer, Wailoa hydropower scheme on Viti Levu, Fiji Electricity Authority • Independent Reviewer, Pit water balance modelling for Latrobe Valley mine closures and setting of appropriate environmental bonds, Department of Economic Development, Jobs, Transport and Resources, Victoria • Expert Reviewer, Water Balance Modelling, Kevin’s Corner Coal Mine, Hancock Coal • Independent Expert Reviewer, Kakamas Hydro-Electric Project, South Africa • Expert Reviewer, Aquatic environmental impacts for the Senex Coal Seam Gas Project EIS AECOM, Queensland
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Annexure B – Curriculum Vitae
• Independent Reviewer, Water balance modelling and sustainable diversion limits, Murray- Darling Basin Authority, Canberra • Auditor, River Crossings and Water Quality: North-South Pipeline Project, Melbourne Water, Victoria • Lead Author, Development of an evaluation framework for NSW water sharing plans, Natural Resources Commission, New South Wales • Expert Witness, Cherry Tree Wind Farm surface and groundwater impacts, Cherry Tree Hill Wind Farm Ltd, New South Wales • Independent Expert Witness, Commonwealth planning tribunal for Moorabin Airport redevelopment, Victoria. Department of Industry, Canberra • Independent Expert, Due diligence assessment of water allocation and availability for power generation. Pacific Energy, New South Wales • Project Director, Hydro lakes water management and development planning, State Planning Unit, Sarawak, Malaysia • Project Director and Peer Reviewer, Hydrological and hydraulic modelling for numerous renewable energy projects in Victoria, Tasmania, NSW, South Australia and Queensland
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Annexure C – Technical Memorandum – ARR 2016 Sensitivity
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Technical memorandum
Date 15 July 2019
To Sallyanne Everett (Clayton Utz)
From Gavin Hay (GHD)
Subject ARR 2016 Sensitivity Assessment – Watsonia Station drain, Banyule Creek and Koonung Creek models
1. Overview Australian Rainfall and Runoff (ARR) is the industry-recognised guideline for undertaking hydrologic investigations in Australia. As described in Part 5.6.1 of Appendix P to the EES (Surface Water) the primary assessment undertaken for the purposes of the EES was based upon the 1987 version of ARR (last updated in 1997). An updated version of ARR was released by Geoscience Australia as a draft for comment in November 2016. A sensitivity analysis was conducted in respect of some components of the project using this updated guideline as documented in Technical Report P. As of 13 May 2019 a final version of the updated guideline has been released (ARR 2019). This technical memorandum contains the outcomes of further sensitivity testing undertaken to understand the potential changes of the project adopting ARR 2016. It focusses on the Watsonia Station drain, Banyule Creek, and Koonung Creek catchments (being the three catchments that were not the subject of sensitivity analysis in Appendix F to Technical Report P). Although this technical memorandum has investigated the effects of ARR 2016 it is likely that the analysis is indicative of the effects of ARR 2019. The results of this analysis extend the sensitivity analysis to include all major cross drainage models and are consistent and not materially different to those already documented in the EES. This publication is prepared to provide information about the North East Link. This publication may be of assistance to you but the North East Link Project (a division of the Major Transport Infrastructure Authority) and its employees, contractors or consultants (including the issuer of this report) do not guarantee that the publication is without any defect, error or omission of any kind or is appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. 2. Background: The 1987 version of ARR, as last updated in 1997, has been adopted for the EES assessment and as the basis of the reference project. In 2017, shortly after the project commenced, Melbourne Water advised that NELP should proceed on the basis of using ARR 1987. Given this advice from Melbourne Water, the characteristics of the project, and the limited experience with and draft status of ARR 2016, the use of ARR 1987 for the EES is considered appropriate. However, in the near future it is expected that further experience with, and updates to ARR 2016, will see its wide spread adoption as the dominant guideline, superseding ARR 1987. Accordingly, it is important to investigate the potential implications of the
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new guidelines (ARR 2016) which recommend significant changes to the data, methods and assumptions used in flood estimation. Note: as of 13 May 2019, the draft ARR 2016 guideline has been replaced by a final version known as ARR 2019. For consistency with the EES this technical memorandum has investigated the effects of ARR 2016, not ARR 2019. Relative to ARR 1987, the recommended data, methodologies and assumptions of ARR 2016 are similar to those of ARR 2019. A sensitivity analysis to better understand the implications of the new guidelines was included in the EES for the following catchments: • Yando Street Main Drain • Kempston Street Main Drain • Yarra River This technical memo extends the sensitivity testing to include the remaining three catchments not tested in the EES: • Watsonia Station drain • Banyule Creek • Koonung Creek Summary results of this sensitivity analysis are provided in Attachment 1. These three catchments were analysed for the 1% AEP event for existing catchment conditions only. The sensitivity assessment focused on existing conditions since previous sensitivity testing confirmed that the use of different design guidelines would influence estimates of the absolute flood levels but would have little impact on the estimates of changes resulting from the works. 3. Approach Updated TUFLOW flood models of existing catchment conditions were used to assess the impact of ARR 2016 on 1% AEP flood levels and depths. The updated model versions included additional information that became available following the release of the EES. The approach used is outlined as follows: • With no adequate calibration data available for Watsonia Station drain and Banyule Creek, and the historic flood data for Koonung Creek (Gauge no 229229A) having 22.5 years of data but no reliable rating curve, all sensitivity modelling adopted recommended design parameters to estimate both the ARR 1987 and the ARR 2016 1% AEP flood conditions. • The suite of ARR 2016 temporal patterns were run through the hydrological (RORB) models of existing catchment conditions (200 runs per AEP in ARR 2016 compared to 20 in ARR 1987). • The ARR 1987 subareas were defined in the normal manner with a characteristic routing reach, impervious fraction and area. RORB’s default filtering of temporal patterns was adopted to remove embedded bursts. • RORB has limited capabilities with respect to ARR 2016. The subarea types of EIA, ICA and PA were separately routed using a purpose built RORB model. Temporal patterns were not filtered for embedded bursts. • For Koonung Creek, the 200 ARR 2016 design storms were run using a coarse grid hydraulic model (TUFLOW). The coarse grid model results for Koonung Creek were used to identify the representative design storms to be run on the fine grid
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model. The results from these representative design storms were selectively blended to generate the representative flood levels throughout the catchment. • For the smaller catchments of Watsonia Station drain and Banyule Creek, it was practical to run the 200 ARR 2016 flows through the ‘fine’ grid TUFLOW model. The model results were mapped using TUFLOW’s mapping utilities. For a given storm duration, the median results from an ensemble of 10 temporal pattern were selected and used to determine the maximum from all durations for a given AEP to form a maximum of the median result. • The ARR 2016 flood level surfaces were compared to the surface from ARR 1987 to determine the change in flood levels (afflux) of adopting the different design guidelines. The afflux surface was calculated by subtracting the ARR 1987 flood level results from the ARR 2016 results, hence positive affluxes represent an increase in flood levels as a result of the ARR 2016 methodologies. Given that the TUFLOW models use the same terrain information, the afflux in flood levels in the catchment is the same as the afflux in flood depths. A summary of these results is provided in Attachment 1, along with figures showing reporting locations and change in flood level (afflux). 4. Results The results for Watsonia Station drain indicate that higher levels were consistently estimated using the ARR 2016 methodology. Generally, observed increases were less than 100 millimetres and most were considerably less than 50 millimetres. There was an area in the rail cut with increases of approximate 130 millimetres, which is influenced by a model boundary and is therefore not indicative of the changes expected (therefore should be ignored). The results for Banyule Creek indicate that higher levels were consistently estimated using the ARR 2016 methodology. Generally, observed increases were less than 100 millimetres. Along the main creek, increases were typically less than 200 millimetres, with an area of ponded water upstream of Lower Plenty Road with increase of up to approximately 950 millimetres. This is upstream of the culverts beneath Lower Plenty Road, and is likely to reflect changes in both the timing and magnitude of the peak flow and well as changes in runoff volume. The results for Koonung Creek indicate that using the ARR 2016 methodology predominantly lower levels were estimated, with only a few small areas of localised increase. Generally, observed decreases were less than 200 millimetres. Along the main creek and road crossings, decreases were more pronounced, with typical values of between 500 to 1000 millimetres. There were also some areas with more significant reductions, such as the storage in Tram Road Reserve, where the decrease was in the order of two metres. 5. Discussion The sensitivity of Watsonia Station drain, Banyule Creek and Koonung Creek catchments to ARR 2016 methodologies were assessed for the 1% AEP flood event for existing catchment conditions. Watsonia Station drain and Banyule Creek showed a trend toward increase in flood levels and depths as a result of applying ARR 2016, while Koonung Creek showed a more significant trend toward decreasing flood levels and depths. These results are compared in Table 4 1 with the sensitivity results included in the EES.
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Table 1 Difference in existing conditions flood estimates between 1987 and 2016 ARR guidelines
Location Source Existing Condition change from ARR 1987 to ARR 2016 Yando Street Main Appendix F of the Absolute levels increased by less than 0.2 m Drain EES Kempston Street Main Appendix F of the Absolute levels increased by less than 0.5 m Drain EES Watsonia Station Current Absolute levels increased by less than 0.1 m drain investigation Banyule Creek Current Absolute levels increased by up to 0.1 m investigation Yarra River Appendix F of the Significantly lower if default parameters EES adopted, however as both ARR 1987 and ARR 2016 models were adjusted to match designated levels, no significant change. Koonung Creek Current Absolute flood levels decrease by up to 1 m investigation
Not surprisingly, these results indicate that using a different methodology on an uncalibrated catchment produces a different result. The smaller catchments to the north showed an increase in flooding, the larger catchments to south a general decrease in flooding particularly where storages are concerned. Given the substantial differences between the ARR 1987 and ARR 2016 methodologies, the small sample of results, indicates that the estimates are remarkably consistent. This consistency is not necessarily representative of other larger or smaller events at this location or for other locations. The differences in estimated flood extents are due to a range of contributing factors. These factors may include the relative size of the catchment, its location, changes to aerial reduction factors, temporal patterns (especially for the longer duration storms), the adopted loss model and its impact on runoff volumes. The variation in the estimated rainfall intensities is also a factor that varies with location and event. Figure 1 illustrates the percentage differences in rainfall depths for the 1 hour 1% AEP storm duration across Australia ( Source: J. Green, C. Jolly, “Comparing the new design rainfalls to at-site rainfall frequency curves”, Hydrology and Water Resources Symposium, 2018 ). Figure 2 illustrates the significant variability in design rainfall intensities across Victoria and Greater Metropolitan Melbourne. Figure 3 provides a project specific comparison of the 1% AEP rainfall depths for the modelled catchments for a range of durations.
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Figure 1 Differences (%) between ARR 2016 design rainfalls and ARR 1987 design rainfalls across Australia for the 1 hour duration, 1% AEP event
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The following was extracted on 4 June 2019 from Bureau of Meteorology www.bom.gov.au/water/designRainfalls/ifd/documents/Melbourne_2016IFDs.pdf
Figure 2 IFD differences in Melbourne (Bureau of Meteorology)
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Figure 3 1% AEP Design Rainfall Depths in mm for a range of durations comparing ARR 2016 vs ARR 1987 IFD data.
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6. Conclusion This additional sensitivity analysis adds to the previous sensitivity analysis documented in the EES and confirms that there are differences which result from applying different design guidelines. The results of this analysis are consistent with the assessment completed and documented in the EES. These results are not materially different to those documented in the EES and as a result this sensitivity analysis does not change the validity of the key findings of the EES. In particular, the Environmental Performance Requirements (EPRs) remain appropriate for the NEL project. These results do help to demonstrate the uncertainty in absolute flood levels for catchments with limited data. In comparison, the differential analysis of impacts used to inform the surface water analysis for the EES are relatively robust. All the sensitivity analysis undertaken demonstrates that the use of the updated Australian Rainfall and Runoff Guidelines produces a different set of design events, which may produce different estimates of flood levels, flow depths, velocities, flow volumes and potentially impacts of construction and operation of the works. It is expected that the impact of the proposed works may vary between different design events, which is the reason why a range of events are assessed, so that the potential impacts are better understood. The above findings are of importance with respect to the setting of absolute levels and estimating the flood immunity of assets. The uncertainty and variation in the absolute estimates of flood levels are one of the reasons why freeboards are added to the estimated design flood levels to provide a level of reassurance that the design intent is being achieved. The sensitivity analysis documented here and within the EES helps to demonstrate that although estimates of absolute flood levels can be somewhat dependant on the choice of ARR guidelines and methodologies, that the robustness of the EPRs and the assessment of project impacts is relatively insensitive to the choice of design guidelines.
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