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

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

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)

WA Coastal Vulnerability Studies 1962 Per Bruun 1987 Searle & Semeniuk 2006-15 WA Coastal Vulnerability Studies 2008-09 WAMSI Node 6.4 2010-13 WA Coast Project 2010-13 Coastal Planning Studies for WA Department of Planning 2011-13 Sediment Cells Definition Studies 2013 Geoscience Australia SLR Study 2013 Geoscience Australia – Coastal Compartments 2013-16 ICOASST Project 2015-16 NCCARF – Phase 2

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.

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

These look awfully familiar… Hey!!! These look awfully familiar…

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

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.

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

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

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

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

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

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

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).

Vulnerability Rankings for Compartments & Cells

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

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.

Problem 2 – Improving Coastal Modelling

Bedform Deflation Phase Qs 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 + −

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

Alternative Models of Coastal Change Dubois(1992)

General Model for Coastal Response to SLR

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)

Southwest: Reef Dominated Coast

Northwest: Tide Dominated Coast & Arid Floodplain

Problem 3 – Using Landform Information

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

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)

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 .

Process Scaling Geomorphic Classification Numerical Modelling Geomorphic Hierarchy

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

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

NCCARF Phase 2

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)

‘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

‘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

‘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

‘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;

‘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