Dune Behaviour and
Management at Stockton Bight
Two Contrasting Case Study Examples
Ainslie Downes, Paul Donaldson, Verity Rollason
NSW Coastal Conference | Terrigal | 31 October 2019
Outline and Aims
Background to Study
• Technical studies for Newcastle coastline /
Stockton Bight dune systems
• Dune management plans prepared for two
sites
• Fort Wallace Site
• Fern Bay Site
Presentation Outline
• Intro / overview
• Processes, risk, management
• Outcomes, challenges, summary
BMT Global
Capability Infographic
What Are Coastal Sand Dunes?
Accumulations of wind-blow sands, usually Dune Morphology
associated with beaches and estuaries • Primary dunes: near to the shore; incl.
• Dune formation: Wind conditions (velocity, incipient dune & foredunes
direction), sediment supply, vegetation and • Secondary dunes: backshore; incl.
moisture content are important factors foredune ridges, blowouts, transgressive
dunes
Schematic Section - Coastal Dunes
Source: Masselink et al. (2003)
What Are Coastal Sand Dunes?
Accumulations of wind-blow sands, usually Dune Morphology
associated with beaches and estuaries • Primary dunes: near to the shore; incl.
• Dune formation: Wind conditions (velocity, incipient dune & foredunes
direction), sediment supply, vegetation and • Secondary dunes: backshore; incl.
moisture content are important factors foredune ridges, blowouts, transgressive
dunes
Schematic Section - Coastal Dunes
Woodroffe (2003), adapted from
Source: Roy et al.
Masselink et(1994)
al. (2003)
Stockton Bight and Study Sites
Stockton (Newcastle) Bight Study Sites Fern Bay
Seaside
• Transgressive sand dune barrier system, • Fort Wallace, Village
young in geological terms (Holocene) Stockton (s) Fort Wallace
• Largest active dune system in Sth. Hemi. DHA Proposal
• Complex and variable wind regime • Seaside Village,
• Dominant SE wind climate: NNE-NE Fern Bay (F)
greatest transport potential (Nicolas, 2016)
Newcastle
F
S
Stockton (Newcastle) Bight Embayment
32 km
Fort Wallace - Dunes and Hazards
Beach and Dunes (Local) Fort Wallace
• High energy (exposed) sandy beach
• Site on S margin of transgressive
dune system (~150m wide; ~15m tall)
• Disturbed, patchy vegetation (w. weeds)
Coastal Processes & Hazards (Regional)
• Harbour breakwaters: Interrupt
N littoral drift, wave shadowing S corner
• Major hazards: historical recession
(sediment deficit), beach erosion (now),
SLR recession (future)
• Minor hazards: dune instability, sand
drift (all timeframes)
Fort Wallace Site, Stockton
Source: Six Maps
Fort Wallace - Dunes and Hazards
Beach and Dunes (Local) Fort Wallace
• High energy (exposed) sandy beach
• Site on S margin of transgressive
dune system (~150m wide; ~15m tall)
• Disturbed, patchy vegetation (w. weeds)
Coastal Processes & Hazards (Regional)
• Harbour breakwaters: Interrupt
N littoral drift, wave shadowing S corner
• Major hazards: historical recession
(sediment deficit), beach erosion (now),
SLR recession (future)
• Minor hazards: dune instability, sand
drift (all timeframes)
Fort Wallace Site, Stockton
Source: Six Maps
Fern Bay - Dunes and Dune Processes
Dune System
• Highly active transgressive dunes Fern Bay
(~600m wide, 20m tall), dune slip face
migrating inland across stabilised
vegetated dunes
• Shoreline building seawards (N littoral
sediment supply)
• Dune slip face moving landwards
(NNE – NE direction)
• Deflation basin growing
• Also, sand mining impacts (late ‘90s to
early ‘00s) around Fern Bay region
[title]
Source: XXX
Fern Bay - Dunes and Dune Processes
Dune System
• Highly active transgressive dunes Fern Bay
(~600m wide, 20m tall), dune slip face
migrating inland across stabilised
vegetated dunes
• Shoreline building seawards (N littoral
sediment supply)
• Dune slip face moving landwards
(NNE – NE direction)
• Deflation basin growing
• Also, sand mining impacts (late ‘90s to
early ‘00s) around Fern Bay region
[title]
Source: XXX
Dunes Transgression / Sand Drift Hazards at Fern Bay
Hazard Classification
• Sand drift – nuisance hazard (no threat)
• Transgressive dune migration – significant
hazard (potential threat)
• Active slip face position indicative of
transgression rates
Hazard Assessment
• Profile slip face measurements
• Contour level chosen for each photogram
profile (need to avoid vegetated dunes)
• Pre and post mining measurement
separated
Typical Dune Morphology
Source: Chevron (2011)
Transgressive Dune Activity
Newcastle Bight
Measured slip face migration:
200 metres in 40 years!
Sub-heading Sub-heading
• Blah • Blah
• Blah • Blah
1994 1954
Sand mining
2001
Transgression marches on…
2013
Fort Wallace (Stockton) Development Proposal
Development Proposal Constraints
• Site 3.2 km north of Harbour (& N exiting • Coastline hazards: aggressive and
residential), spanning beach to Fullerton St. progressive erosion; future climate risks
• Former defence site Note: dune movement not a key issue
• Existing: hummocky dunes, sparsely • Heritage features
vegetated (w. weeds), historical structures Opportunities
• Proposed: Rezoning for residential; enviro • Areas of undeveloped backbeach land
/ reserves (SP2 > R2, E3, RE2) • Restore / improve degraded dune ecology
Coastal Risk Management - Fort Wallace (Stockton)
Management Aims and Objectives
• Incorporate coastal hazards into the master
planning process
• Implement a program of dune rehabilitation and
ongoing dune maintenance on the site
Master Planning
• Hazard and risk guided master planning process
(location and form of development)
• All development set back behind unlikely 2100 hazard line
• Higher density housing sited differently
• Good planning outcome!
Fort Wallace Site, Hazard Setbacks & Master Plan
Source: BMT (2019)
Coastal Risk Management - Fort Wallace (Stockton)
Dune Management Plan (DMP)
• DMP prepared for risk mitigation
• Key outcomes sought:
• encourage sand capture to buffer for erosion
• mitigate nuisance sand drift
• Added benefit: remove weeds; improve dune ecology; &
encourage ecological stewardship (future local community)
• Short- and medium-term actions
• Rehabilitation specification for the dunes
• Ongoing maintenance regime and storm response actions
• Long-term actions:
• Erosion trigger point to indicate additional actions required
Dune Management Plan for Fort Wallace
Source: BMT (2019)
Coastal Risk Management - Fort Wallace (Stockton)
Fern Bay Seaside Village Development Site
Development Proposal
• Site 7km north of Harbour, & nearly 1km
landward of the shoreline
• Development on stabilised vegetated dunes,
landward of active transgressive dune front
• Surrounded by reserve (Worimi RP & SCA)
Conditions of Consent
• Dune Management – prepare Dune
Management Plan (DMP) to manage risk,
prior to issue of the final subdivision cert.
• DMP to be implemented by the Community
Association in perpetuity!
Seaside Village Mater Plan, Fern Bay
Source: Rawson Communities
Coastal Risk – Fern Bay
Dune Transgression Hazards
• Key hazard to consider - transgressive dune
potential to engulf development
• (Nuisance) sand drift – minor concern
• Measured transgression rates (region average):
0.4 m/yr to 3.4 m/yr (increasing moving North)
• Adopted rates and timeframe to impacts:
Lower: 0.5 m/yr, 2615 timeframe
Middle: 2.0 m/yr, 2165 timeframe
Upper: 3.5 m/yr, 2100 timeframe
Upper w CC: 4.0 m/yr, 2090 timeframe
Dune Transgression Hazard Estimates
Source: BMT, 2019
Coastal Risk Management – Fern Bay
Management Aims and Objectives
• Identify appropriate actions and measures required
to reduce adverse impacts on the development in
the event that the transgressive dunes encroach on
the development in the future
• Satisfy conditions of consent dune management
requirements
Development Siting
• Differs to Stockton site, very long-term risk to site
• Development setback at significant distance from
the shoreline – will not be an issue for many
decades, if at all.
Seaside Estate Aerial
Source: Blue Wave Property Strategies
Coastal Risk Management – Dune Management Plan
• Dune Management Plan developed for risk mitigation
• Trigger based adaptive management plan was prepared
• Aims of DMP:
• Avoid modifying natural dune landscape values
• Understand dune behaviour changes and condition
• Implement appropriate mitigation measures
• Dune toe migration monitoring regime with various trigger points
• Monitoring involves surveying dune toe at 10 yearly intervals, with
trigger to increase monitoring if/when toe is 80 metres from the
development (equivalent to a 20-year timeframe until impact)
• Revegetation not considered appropriate due to active dune values
• Appropriate and permissible future mitigation measures unknown
Fern Bay Dune Management Report
Source: BMT (2019)
Project Challenges – Dune Management
• Coastal risks – understanding the physical
processes to guide site planning and
management
• Capacity building – bringing the clients up to
speed with coastal processes and risks
• Community title development – need to
prepare fit for purpose management plans that
aren’t overly onerus / burdening on the
community
• Cross jurisdictional issues – Worimi
Aboriginal Lands, Council and other
neighbouring land owner management goals
and plans
Summary
Fort Wallace Fern Bay
Dune Condition and Processes Dune Condition and Processes
• Sited on margin of transgressive dunes • Highly mobile, transgressive dune system
• Dune partially vegetated (weeds) and stable • Development on stable vegetated dunes
Key Hazard landward of transgressive dune toe
• Coastal erosion and recession (long-term) Key Hazard
Management Response • Dune transgression (very long-term)
• Risk based master planning Management Response
• Dune management plan focused on retaining • Trigger based adaptive dune management
sand and ecological outcomes plan, focused on monitoring landward
movement of the transgressive dune toe
Ainslie Downes, BMT
Environmental Scientist
Thank you Ainslie.Downes@bmtglobal.com
www.linkedin.com/in/ainsliedownes/
Paul Donaldson, BMT
Senior Coastal Scientist
Paul.Donaldson@bmtglobal.com
www.linkedin.com/in/donaldson-paul/
Verity Rollason, BMT
Principal Coastal Scientist
Verity.Rollason@bmtglobal.com
BMT’
Newcastle
(02) 4940 8882
