Grange Planning Brain

title: Planning Scheme Amendment to Implement Kyneton, Lauriston, Tylden and Malmsbury Flood Studies council: macedon-ranges state: vic category: amendment classification: MAJOR status: in-progress last_compiled: 2026-05-31 source_docs:

  • final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf
  • web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-24235bf252.txt
  • kyneton-and-carlsruhe-overall-map.pdf
  • kyneton-flood-study-frequently-asked-questions.docx
  • kyneton-flood-study-frequently-asked-questions.pdf
  • web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt
  • tylden_rapid_flood_risk_assessment.pdf
  • malmsbury_rapid_flood_risk_assessment.pdf
  • lauriston_rapid_flood_risk_assessment.pdf

Planning Scheme Amendment to Implement Kyneton, Lauriston, Tylden and Malmsbury Flood Studies

This amendment is a hazard-mapping implementation project: it is intended to translate updated North Central Catchment Management Authority flood modelling into the Macedon Ranges Planning Scheme through revised Land Subject to Inundation Overlay mapping and, for parts of Kyneton, a new Floodway Overlay. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) Its practical planning effect is not to fund drainage works, but to change which land is screened for flood risk before buildings, works or subdivision proceed. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.2)

Background

The amendment sits within Council’s adopted 2025-2035 strategic program: the Year One Action Plan directs Council to commence a planning scheme amendment process to implement flood studies for Kyneton, Lauriston, Tylden and Malmsbury prepared by North Central Catchment Management Authority. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.942) That action implements the broader objective to reduce environmental risks, including bushfire, storm and flood, in land use planning. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.788)

The technical base has two layers. Kyneton and Carlsruhe are based on the Kyneton Flood Study 2019, which Council says used updated data and detailed modelling of the Campaspe River and Post Office Creek through Kyneton. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) Lauriston, Malmsbury and Tylden are based on Rapid Flood Risk Assessments completed for North Central CMA in 2020 as part of a 21-township regional program. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.4; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.4; Source: tylden_rapid_flood_risk_assessment.pdf, p.4)

The immediate trigger for the amendment is a climate-change update. Council’s consultation page states that Australian Rainfall and Runoff guidance was updated in August 2024 to provide specific advice on climate-change considerations for flood modelling, and that North Central CMA then updated the Kyneton Flood Study and the Tylden, Malmsbury and Lauriston assessments to incorporate those considerations. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)

Analysis

Statutory Mechanism

The core mechanism is overlay accuracy. The Land Subject to Inundation Overlay applies to land designated as subject to inundation in the 1% Annual Exceedance Probability flood, commonly described as a 1-in-100-year flood. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.2) The overlay does not prohibit all use or development; it triggers planning assessment so proposals can be designed in a way compatible with the flood risk of the site. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.2)

North Central CMA has two statutory roles relevant to this amendment. It is the floodplain management authority for the North Central region by delegation from the Minister responsible for the Water Act 1989, and it is a recommending referral authority under section 55 of the Planning and Environment Act 1987 for subdivision and development applications within floodplains. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.1) Council remains responsible for local drainage and stormwater overflows from its drainage system, which means the amendment separates catchment-scale riverine flood mapping from local drainage asset management. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.1)

The Floodway Overlay has a narrower hazard function than the LSIO. Council’s 2025 consultation material states that the FO is applied to inundated land with higher hazard levels due to greater water velocity and depth, while the LSIO identifies land subject to inundation in the 1% AEP event. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) That distinction matters because the amendment is not simply enlarging a general flood map; it is sorting mapped floodplain into different statutory risk categories.

Kyneton and Carlsruhe

Kyneton is the most consequential mapped area because the proposed change includes both a new FO and LSIO for areas of Kyneton, while the smaller settlements are described as LSIO changes. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) Council’s earlier flood-mapping review states that the existing Kyneton mapping was based on geological mapping with very low or uncertain reliability, and that there had not previously been a comprehensive flood study for Kyneton and Carlsruhe. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.1)

The Kyneton/Carlsruhe overall map shows the proposed and existing LSIO along the Campaspe River, Little Coliban River, Post Office Creek, Pipers Creek and Ritchies Creek, with mapped floodplain running through and around the town rather than being confined to one edge of the settlement. (Source: kyneton-and-carlsruhe-overall-map.pdf, p.1) The planning implication is that amendment effects are likely to be parcel-specific: some land will move into an overlay, some land may remain within existing controls, and some existing LSIO extent may be reduced where the new model indicates lower risk. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-24235bf252.txt)

The Kyneton documents available in this corpus do not provide the parcel count, affected land area, flood depths, velocity bands or number of buildings affected by the proposed LSIO and FO. (Source: kyneton-and-carlsruhe-overall-map.pdf, p.1; Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) That is a material analytical gap because Kyneton is the only location where the amendment is described as introducing a new Floodway Overlay, and FO mapping normally has stronger implications for built form, access, flood storage and evacuation risk than LSIO-only mapping. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)

Tylden: Frequent Road Overtopping and Stable Property Count

The Tylden rapid assessment covers a township of approximately 236 people upstream of Upper Coliban Reservoir, with the Little Coliban River and Jones Creek south of the town and an unnamed creek flowing north-east through the town. (Source: tylden_rapid_flood_risk_assessment.pdf, p.6) The upstream catchment area is 41 square kilometres, which makes Tylden a small-catchment flood setting where local catchment subdivision and road crossings can materially affect mapped hazard. (Source: tylden_rapid_flood_risk_assessment.pdf, p.6)

The modelled peak flow at the downstream end of the Tylden study area rises from 27.2 cubic metres per second in the 20% AEP event to 65.1 cubic metres per second in the 1% AEP event, with a 36-hour critical duration for those events. (Source: tylden_rapid_flood_risk_assessment.pdf, p.25) In land-use terms, the key sensitivity is not a large increase in the number of affected properties across event sizes: the report shows five residential properties and one industrial property inundated for every modelled event from 20% AEP through 0.5% AEP. (Source: tylden_rapid_flood_risk_assessment.pdf, p.37)

The sharper Tylden issue is road performance. Tylden-Woodend Road is overtopped even in the 20% AEP event, with modelled depth increasing from 0.2 metres for 18 hours in the 20% AEP event to 0.6 metres for 36 hours in the 1% AEP event. (Source: tylden_rapid_flood_risk_assessment.pdf, p.38) Two residential buildings are modelled as subject to over-floor flooding across all modelled events, but the floor levels are partly assumption-based where surveyed floor levels were unavailable. (Source: tylden_rapid_flood_risk_assessment.pdf, p.37)

Climate-change sensitivity increases the planning justification for updated controls. Under the report’s RCP 8.5 scenario, Tylden’s 20% AEP peak flow increases from 22.6 to 27.2 cubic metres per second, and its 1% AEP peak flow increases from 54.8 to 65.9 cubic metres per second. (Source: tylden_rapid_flood_risk_assessment.pdf, p.40) The report states that, under RCP 8.5, the current 20% AEP event should be considered against the 10% AEP map, the current 10% AEP event against the 5% AEP map, and the current 5% AEP event against the 2% AEP map. (Source: tylden_rapid_flood_risk_assessment.pdf, p.41)

Malmsbury: Regulated River, Highway Constraint and Sports Ground Exposure

Malmsbury has a different flood mechanism because the Coliban River is significantly regulated by Upper Coliban, Lauriston and Malmsbury Reservoirs upstream of the town. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.6) The township is immediately downstream of Malmsbury Reservoir, has a population of approximately 831, and sits within a 289 square kilometre upstream catchment. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.6)

The modelled peak flow at Malmsbury rises from 98.9 cubic metres per second in the 20% AEP event to 213.9 cubic metres per second in the 1% AEP event, with the critical duration reducing from 72 hours in smaller events to 48 hours in the 1% AEP event. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.30) The report records no inundated properties in the 20% AEP event, two public properties inundated from the 10% AEP through 1% AEP events, and three residential plus three public properties inundated in the 0.5% AEP event. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.42)

The main access and infrastructure constraint is Mollison Street, identified as the Calder Highway in the impact table. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.41) The model shows Mollison Street overtopped from the 5% AEP event, with depth increasing from 0.1 metres for 4 hours in the 5% AEP event to 0.2 metres for 15 hours in the 1% AEP event and 0.4 metres for 21 hours in the 0.5% AEP event. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.43) That makes the amendment relevant not only to private-property assessment but also to emergency access and movement planning around the Calder Highway corridor. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.43)

Malmsbury’s climate-change sensitivity is stronger than Tylden in map-equivalence terms. Under RCP 4.5, the current 20% AEP event is treated as equivalent to the 10% AEP map, while under RCP 8.5 the current 20% AEP event is treated as equivalent to the 5% AEP map. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.46) For the 1% AEP event, peak flow increases from 207.8 to 226.9 cubic metres per second under RCP 4.5 and to 249.8 cubic metres per second under RCP 8.5. (Source: malmsbury_rapid_flood_risk_assessment.pdf, p.45)

Lauriston: Reservoir-Influenced Riverine Risk with Limited Road Impact

Lauriston is downstream of Lauriston Reservoir and has an upstream Coliban River catchment of 221 square kilometres. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.6) Like Malmsbury, its flood behaviour is affected by upstream storages, with the report noting significant regulation by Upper Coliban and Lauriston Reservoirs. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.6)

The modelled peak flow at Lauriston increases from 58.5 cubic metres per second in the 20% AEP event to 229.6 cubic metres per second in the 1% AEP event. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.29) The property-impact threshold is higher than Tylden: no properties are modelled as inundated in the 20%, 10% or 5% AEP events, while four residential properties are modelled as inundated in the 2%, 1% and 0.5% AEP events. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.41)

Over-floor flooding in Lauriston increases between the 2% and 1% AEP events: two residential properties are modelled above floor in the 2% AEP event and three residential properties in the 1% and 0.5% AEP events. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.41) Unlike Tylden and Malmsbury, Lauriston Road is shown with zero modelled depth and zero duration across all assessed AEP events. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.42)

Climate change still changes the statutory risk picture. Lauriston’s 1% AEP peak flow increases from 231.2 cubic metres per second under current climate to 252.5 cubic metres per second under RCP 4.5 and 277.9 cubic metres per second under RCP 8.5. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.44) Under RCP 8.5, the current 10% AEP event is mapped as equivalent to a 5% AEP event and the current 5% AEP event is mapped as equivalent to a 2% AEP event. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.45)

Model Reliability and Statutory Caution

The Lauriston, Malmsbury and Tylden reports are explicitly rapid assessments, not detailed site-specific flood studies. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.4; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.4; Source: tylden_rapid_flood_risk_assessment.pdf, p.4) Each report states that the rapid nature of the work precluded detailed site-specific studies, extensive model calibration and community engagement. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.4; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.4; Source: tylden_rapid_flood_risk_assessment.pdf, p.4)

The shared modelling platform is still more robust than old geological mapping because each report used Australian Rainfall and Runoff 2019 hydrology, available LiDAR terrain for the full study area, RORB hydrology and TUFLOW hydraulic modelling. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.51; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.52; Source: tylden_rapid_flood_risk_assessment.pdf, p.47) The main statutory caution is that the TUFLOW parameters were not calibrated or verified to recorded flood levels in all three rapid assessments. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.51; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.52; Source: tylden_rapid_flood_risk_assessment.pdf, p.47)

The reports also identify common limitations: no independent survey check of LiDAR terrain, possible under-representation of waterways less than eight metres wide, reliance on statewide VLUIS land-use data for roughness, and no method in ARR2019 to account for potential increases in rainfall losses under a drying climate. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.52; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.53; Source: tylden_rapid_flood_risk_assessment.pdf, p.48) These limitations do not invalidate the amendment, but they mean future permit decisions may still require site-specific flood levels, floor-level survey, hydraulic advice or referral conditions. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.3)

Current Status

The consultation material identifies Stage One as 3-31 March 2025, when directly affected residents could provide initial feedback on the studies and flood mapping. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) Stage Two is listed as a future planning scheme amendment to introduce the mapping changes into the Macedon Ranges Planning Scheme. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)

Council’s adopted 2025-2035 action plan confirms that the next procedural step is to commence the amendment process. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.942) The consultation page states that Council will seek authorisation from the Minister for Planning, exhibit the proposed changes through the amendment process, work with North Central CMA to resolve issues, and refer unresolved issues to an independent Standing Advisory Committee established for flooding matters. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)

Dependencies

  • Blocks: Final statutory recognition of the updated Kyneton, Lauriston, Tylden and Malmsbury flood mapping in the Macedon Ranges Planning Scheme is blocked until the amendment is authorised, exhibited, considered and approved. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)
  • Blocked by: The amendment depends on Ministerial authorisation, public exhibition, resolution of submissions, and any Standing Advisory Committee process for unresolved objections. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)
  • Informed by: The technical base includes the Kyneton Flood Study 2019, Kyneton 2024 Climate Change Addendum, Lauriston/Malmsbury/Tylden 2025 Climate Change Addendum, and the 2020 rapid assessments for Tylden, Malmsbury and Lauriston. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)
  • Implements: The amendment implements Council’s 2025-2035 action to reduce flood risk through land-use planning and to commence the flood-study amendment process. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.942)
  • Conflicts with: No direct policy conflict is documented in the available source set; the practical tension is between using rapid-assessment mapping for statutory controls and the reports’ own caution that more detailed local studies may be needed for some decisions. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.52; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.53; Source: tylden_rapid_flood_risk_assessment.pdf, p.48)

The amendment depends on North Central CMA as the floodplain management authority for the northern part of the shire, while Council remains responsible for local drainage and stormwater management. (Source: kyneton-flood-study-frequently-asked-questions.pdf, p.1) The rapid assessments were funded through a joint Victorian and Australian government initiative and formed part of a 21-township regional program across the North Central CMA region, so the Macedon Ranges amendment is one local statutory implementation of a broader regional flood-risk program. (Source: lauriston_rapid_flood_risk_assessment.pdf, p.4; Source: malmsbury_rapid_flood_risk_assessment.pdf, p.4; Source: tylden_rapid_flood_risk_assessment.pdf, p.4)

Council’s asset planning shows why the amendment should not be read as a drainage-capital-works package. Council’s stormwater drainage network had an estimated replacement value of about $96.5 million as at 30 June 2024, comprising 316.6 kilometres of stormwater pipes, 11,857 pits and 70 drainage basins. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.924) The same asset plan states that Council does not yet have structured condition information for stormwater assets and that the ability of the stormwater network to withstand climate-change impacts is yet to be determined. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.925) The amendment therefore manages development exposure to mapped riverine and waterway flooding, while separate asset-planning work remains necessary for local drainage capacity, renewal and flood-immunity upgrades. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.925)

Gaps in This Analysis

The main corpus gap is the absence of the full Kyneton Flood Study 2019 Final Report, Kyneton Flood Study 2024 Climate Change Addendum, and Lauriston/Malmsbury/Tylden Rapid Flood Risk Assessment Climate Change Addendum 2025, even though Council’s consultation page lists them as reference documents. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) Without those documents, this page cannot quantify the Kyneton FO/LSIO land area, parcel count, modelled depths, velocity categories, floodway criteria or property-level effect. (Source: kyneton-and-carlsruhe-overall-map.pdf, p.1)

The second gap is the absence of the amendment documentation itself: no amendment number, explanatory report, instruction sheet, proposed planning scheme maps, exhibited schedule changes, officer report on submissions or advisory committee material is present in the source set. (Source: final-agenda-attachments-council-meeting-22-october-2025-reduced.pdf, p.942; Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) Until those documents are available, the amendment can be described as an in-progress implementation process, but not as an exhibited or approved statutory control. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)

The third gap is consultation substance. The available material states that Stage One ran from 3-31 March 2025 and that later unresolved issues may go to a Standing Advisory Committee, but it does not provide submission counts, issue categories, agency positions or property-owner concerns. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt) That prevents a reliable assessment of contested issues, likely mapping changes before adoption, or the scale of site-specific objections. (Source: web-research-L0-flood-study-technical-reports-for-kyneton-lauriston-tylden-and-malmsbury-evidence-f02ba876c7.txt)

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