1. South Australian Coastal Conference 13 November 2015
Sediment Compartments and Landform Frameworks for Coastal Management and Planning
Matt Eliot
Damara WA Pty Ltd
Supported by NCCARF Phase 2

2. Key Lessons Learned
A situation of coastal diversity lends itself to the use of landform-based coastal vulnerability assessment Planning requires consideration of multiple scales and disciplines, implying value in a geomorphic hierarchy The divergence between models and landform assessment provides opportunity for additional information that can be used for model process selection or model verification Hierarchical relationships can be used as a framework for developing increased complexity in coastal change assessment

3. Acknowledgements Supporting Organisations NCCARF (Phase 2)
Geological Survey of Western Australia Department of Planning Department of Environment &
Conservation Department of Transport Geoscience Australia Department of Climate Change WAMSI Program Oceans Institute (UWA)
Staff
Damara WA
Ian Eliot
Matt Eliot
Tanya Stul
Glenn McCormack
GSWA
Bob Gozzard
DEC
Chris Nutt
Ewen Buckley
Project Champions
Bruce Thom
(Wentworth Group)
Charlie Bicknell (Transport)
Vivienne Panizza (Planning)
Martine Woolf (GA)
Martyn Hazelwood (GA)
Chari Pattiaratchi (SESE)

4. WA Coastal Vulnerability Studies
1962
Per Bruun
1987
Searle & Semeniuk
WA Coastal Vulnerability Studies
WAMSI Node 6.4
WA Coast Project
Coastal Planning Studies for WA Department of Planning
Sediment Cells Definition Studies
2013
Geoscience Australia SLR Study
2013
Geoscience Australia – Coastal Compartments
ICOASST Project
NCCARF – Phase 2

5. Sediment Compartments
A sediment compartment is a spatial unit that defines a section of coast within which coastal behaviour is coherent.
Terminology and means of definition vary globally, and has varied over the course of various studies.
Some distinction between the geological framework and the sediment transport can be made, but the distinction is clearly evident only for small parts of Australia.
Work progressing through NCCARF Phase 2 (presently) combines the concepts.
Use of sediment compartments is an ‘old’ concept. It was most popular in the 1980s, before the advent of numerical modelling.
It remains the basis for much of our coastal management.

6. Sediment ‘Cell’ Approach
Applied internationally since 1966 using multiple approaches, including hierarchies.
Our definition: Sediment cells are sections of coast within which sediment transport processes are strongly related.
Not just source, sinks and pathways as there may be multiple ones with reversals. Focusing on the ‘relationship’. Considered holistically as the assemblage of marine and terrestrial landforms contained within the cell together with landform connectivity.
Factors to consider:
Leakiness: Cells are not always self-contained units
Boundary reversibility and migration
Rivers and sand feeds as boundaries
Rock and engineered structures
Non-coincidence of boundaries through scales
Davies 1973
HR Wallingford 1997

7. These look awfully familiar…
Hey!!!
These look awfully familiar…

9. Landform Frameworks
A landform framework describes the inter-relationships between geomorphic units.
The framework should be applicable over a range of scales.
At small scales, the landform framework describes how the various landform elements fit together (e.g. beach, foredune, primary dune).
At each scale, it should describe sediment transfers and support characterisation of key processes.
In general, there is a relationship between time and space scales – resulting in a change of disciplines!
Image: Coast Protection Board 2008
From Limestone Coast and Coorong Coastal Action Plan

10. Coastal Systems Mapping
Approach follows:
French JR & Burningham H (2009) Mapping the connectivity of large scale coastal geomorphological systems: Coastal system mapping with CmapTools tutorial. Science Report – SC060074/PR2. Bristol, Environment Agency, 25pp.

11. Process Identification & Scales
Nearshore Diversity?
Swell? Alongshore?
INSET D
Scales
INSET B
(A) Curvature of Geographe Bay reflects diffraction of prevailing swell around Cape Naturaliste
(C) Nearshore sandbars
respond to swell, tide and
nearshore currents
INSET C
(B) Pattern of
offshore ridges and canyons
provides wave focus and dispersion
(D) Coastal salients developed where sandbars are large or concentrated
Offshore Focusing?
Onshore Supply? Alongshore Transport

12. Problem 1 – Trying to find relationships between information at different scales…

13. Finer Resolution Required & Change in Information of Interest
Planning Scales
Marine Habitat Management
Strategic Land-use Planning
Regional Land-use Planning
Local Land-use Planning
Erosion Management
Coastal Adaptation
Finer Resolution Required & Change in Information of Interest

14. Geomorphic Hierarchy
Zones: Broad sectors of the Australian continent based on climate
Divisions: Provides an overview of the whole state suitable for maps at scales of about 1:5,000,000
Provinces: Areas defined on geomorphologic or geological criteria suitable for regional perspectives at scales of about 1:1,000,000
Regions: Areas with recurring patterns of landform and geology suitable for regional mapping at scales of approximately 1:250,000

15. Geomorphic Hierarchy
Land Systems: Areas of characteristic landform patterns suitable for mapping at regional scales of 1:50,000 to 1:100,000
Compartments: A local unit based on one or more definite landforms suitable for mapping at scales of about 1:25,000 to 1:50,000
Sediment Cells: A local unit based on several linked landforms suitable for mapping at scales of about 1:5,000 to 1:25,000
Landforms: A local unit based on one or more landforms suitable for mapping at scales of about 1:5,000 to 1:15,000

16. Landform Vulnerability Assessment Approach
An extreme event or events cause change to the type or location of a land system.
eg. Avulsion and delta shift
Policy Focus
(Measurable?)
Policy Allowance
(Guesses!) =
VULNERABILITY
STABILITY +
SUSCEPTIBILITY
Likelihood of landform and/or land system change
Likelihood of erosional change to landforms related to current land surface condition
Likelihood of structural breakdown leading to a change in the land system
Gradual landform change associated with land surface instability ultimately results in structural change.
eg. Barrier evolution

17. SANDY (BARRIER) COAST SUSCEPTIBILITY
Rank 1: Episodic Transgressive Barrier
Nested blowouts and parabolic dunes.
Rank 2: Prograded Barrier
Low, foredune ridge plain
Rank 3: Stationary Barrier
Low or narrow ridge of blowout
The susceptibility of a sandy barrier refers to the intrinsic propensity of the structure comprising the barrier system to alter in response to projected change in metocean conditions, particularly sea level rise over.
Barrier formation occurs over a long period, commonly millennia, although structural change from one type to another may occur within tens to hundreds of years.
Rank 4: Receded Barrier
Low narrow dune ridge & old shoreline
Rank 5: Mainland Beach
Narrow duns & beach abutting bedrock.
SANDY (BARRIER) COAST SUSCEPTIBILITY
The sequence illustrated here follows that described by Roy (1994).

18. Vulnerability Rankings for Compartments & Cells

19. Combined Scales of Vulnerability Rankings
Implied result is a set of scales at which coastal behavior can be related
Key
Vulnerability
Implications for Development
Low
Coastal risk not considered a constraint to development
Low-to-moderate
Coastal risk may present a low constraint to development
Moderate
Coastal risk may present a moderate constraint to development
Moderate-to-high
Coastal risk is likely to be a significant constraint to development
High
Coastal risk is a highly significant constraint to development

20. Approximate Planning & Management Scale Relative Landform Scale
Process Scale
Local Area
Sub-regional
Regional
Primary Cells
Inner continental shelf
Offshore reefs & islands
Holocene sediment banks
Upper shoreface
Barrier systems
Deltas & estuaries
Centuries
Secondary Cells
Inshore reefs & islands
Sediment banks
Upper shoreface
Frontal dunes, foredune plains & parabolic dunes
Shoals of streams & estuaries
Decades
Years
Tertiary Cells
Subtidal terrace
Nearshore morphology
Beachface (beach & berm)
Rock outcrops
Foredunes
Active frontal dunes
Seasons
Days
Small (Landforms)
Moderate (Landforms)
Large (Land Systems)
Relative Landform Scale
UP AND DOWN SCALING
Scale determines the principal coastal processes driving landform changes and the sediment budgets that underpin them. The scale of coastal sediment cells should be commensurate with the scale of processes potentially impacting on the planning proposal or project in the relevant management timeframe, together with the scale required to consider impacts of planning proposal or project on the coast.

21. Problem 2 – Improving Coastal Modelling

22. Bedform Deflation PhaseQs
Models
Planar bed
Constant bedform
Bedform response
Reality
Bedform Growth Phase
Bedform Deflation Phase
Simple models provide opportunity for systematic dislocation between model and reality, with consistently biased results
Example is exaggerated erosion hazard when neglecting erosion- recovery processes u
Planar Bed Bias + −
Constant Bedform Bias + −
Bedform Response Bias + −

23. Applicable Coast Types Result is a function of model applicability!
Dominant Processes
Secondary Processes
Model Method
Result is a function of model applicability!
Marginal Coast Types
Signal
“error”
Bias
Secondary Processes
Dominant Processes
“error”
Reality
Parameter 2
Model
Model
Bias
Applicable
Marginal
Signal
Parameter 1

24. Alternative Models of Coastal Change
Dubois(1992)

26. General Model for Coastal Response to SLR

30. Effect of scale on processes
Many assessments only use few elements. Reality includes a cascade of processes with identification limited by perception of time and space scales.
Example: Comet Bay
Effect of scale on processes
Complex interactions of sediment transport and inlet-ocean exchange
Comet
Bay
(Stul et al. 2012)

31. Southwest: Reef Dominated Coast

34. Northwest: Tide Dominated Coast & Arid Floodplain

35. Problem 3 – Using Landform Information

36. Landform – Model Relationships
Default Use
Conceptual Model
Increased degrees of freedom & model parameterisation
Landforms
Connectivity
Active Processes
Scales of Response
Response Amplitude
Empirical Model
Statistical Model
Sadistical Model
Analytical Model
Model Domain
Model Scales
Active Processes
Numerical Model
Landform Analysis can be used to assist model formulation through:
Complexity of model conceptualisation
Refining investigation boundaries
Improve process selection and valid representation
Determine process-scale relationships
Consider short and long-term coastal vulnerability

37. Basis for Landform Assessment
Land systems and landforms develop as aggregated result of many years of process-response for both active and extreme processes.
There is a GENERAL pattern that finer resolution landforms respond to more shorter time-scale processes
SCALE
Study Scales
Extrinsic Conditions
Main Components
Noise / Residual Effect
Sampling Scales
Study Limits
Process Scales
Short Scales
Long Scales
A key outcome is that there is a change in discipline: from geology, through geomorphology to coastal engineering.
(After: Wright & Thom 1977)

38. Regional Process Scaling
After: McLean (2000)
Need to work between scales by moving both up and down.
A few examples of factors to consider:
Rock or other structural controls (+leakiness)
Rivers or sand feeds
Shelf and basin interaction
Feature Feedback and importance of scale of observation .

39. Process Scaling Geomorphic Classification Numerical Modelling
Geomorphic Hierarchy

40. A few Conclusions about Compartments
Looking at coherence for coastal management
Determines an appropriate ‘style’ of coastal management
Provides a potential scale in which to identify active processes
Provides a basis for looking ‘down’ to model scales

41. A few Conclusions about Landform Frameworks
Landform analysis is a fundamental tool of coastal engineering that has seen reduced application with increased prevalence of numerical modelling
Interpretation of land systems and landforms may:
Improve model performance through
Assisting with selecting model scaling, processes and complexity
Describing boundary conditions
Providing validation if same information is not used for model calibration
Provide a framework for upscaling and downscaling of coastal change assessments
Offer a proxy for long-term coastal landform vulnerability

42. NCCARF Phase 2

43. Sediment Compartments Research Project
NCCARF Phase 2
Sediment Compartments Research Project
Available expert knowledge identifying coastal compartments has been developed as a spatial database (Geoscience Australia)
It is proposed to characterise the database with information that describes how each compartment behaves, in a coastal sense
Key attributes include prevailing and dominant meteorological drivers; tendency to be open or closed; whether there is an external source of sediment supply; and the general nature of alongshore transport (high / low, dominant / oscillatory / episodic)

44. ‘Soft Coasts’ Information Manual
NCCARF Phase 2
‘Soft Coasts’ Information Manual
Context and Content
Soft shores, including beaches, banks and coastal terraces are the features first affected by coastal dynamics, including any response to changes of climate.
Soft shores commonly provide a buffer to erosion-recovery cycles, and therefore management of soft shores may provide an important means of influencing coastal resilience.
What are the issues?
Causes and impacts of coastal dynamics – storms, SLR, human impacts
Coast Types
Alongshore and cross-shore coastal dynamics.
Beaches as damping mechanisms for coastal stress
Erosion-recovery cycles
Dune management: sediment sink; erosion buffer; ecological community
Transfer of coastal stresses

45. ‘Soft Coasts’ Information Manual (continued)
NCCARF Phase 2
‘Soft Coasts’ Information Manual (continued)
Large scale coastal dynamics
Sediment sources, pathways and sinks
River of sand concept
Coastal systems mapping
Sediment compartments
Sediment budgets
Balancing the budget: shelf sediments, dunes and floodplains

46. ‘Soft Coasts’ Information Manual (continued)
NCCARF Phase 2
‘Soft Coasts’ Information Manual (continued)
Available data accessible to you
Coastal data typically used: aerial imagery, wave and water level observations, beach profiles, sediment grain size
Common information sources:
Smartline
NCCOE Framework
ACE-CRC Generic Erosion Allowances
OZ Estuaries
Coastal Compartments
Professional Advice
State-relevant information: e.g. South Australian Coastal Action Plans

47. ‘Soft Coasts’ Information Manual (continued)
NCCARF Phase 2
‘Soft Coasts’ Information Manual (continued)
What you can do to respond
Develop a greater understanding of your coast
Establish your history
Reduce sensitivity to coastal change through appropriate land-use, intelligent siting and design of infrastructure
Develop alongshore and cross-shore development buffers, that may support active management
Decision-making Frameworks
Distinguishing cyclic and progressive change
Setting management triggers and actions
Understanding adaptation hierarchies
Coastal Monitoring: photo monitoring, informal measurements
Professional Assessments: sedimentary analysis; deterministic / probabilistic modelling;

48. ‘Soft Coasts’ Information Manual (continued)
NCCARF Phase 2
‘Soft Coasts’ Information Manual (continued)
Tips and traps
Understanding that erosion is expected.
Working with nature: recognising the financial implausibility of fighting nature
Use of rules of thumb in decision-making (pros and cons)
Over-reliance on policy-based assessment.
Foreshore setbacks are widely used as the preferred mechanism
Application of Bruun ratio commonly used, with no alongshore variation
Coping with shifting policy and practices at State and Local Level.
Ignoring rock – at one’s own peril
Beware coastal modelling: stating the obvious
Common principles for management:
Foreshore setback
Hydraulic smoothness
Nodal development