Western Australian landscapes, soils and vegetation

Landscapes, Soils & Surface Environments - Workshop 2b

Raphael Viscarra Rossel, Lewis Walden

2026-02-17

Recap

  • We saw four broad Australian physiographic regions:

  • We linked them to:

    • Different soils
    • Different vegetation

  • We used hillslopes and catenas to explain soil–water–vegetation changes downslope

Now: zoom into a specific Western Australian landscape region.

Our study area: Swan Coastal Plain to Darling Scarp

We’ll use this area to study throughout the unit. It includes:

  • Coastal dunes, Swan Coastal Plain, Perth Basin, Darling Scarp and Yilgarn Craton margin.
  • Includes Banksia woodlands, wetlands, jarrah–marri forests and urban areas.
  • Elevation rises from ~0 m at the coast to ~300 m on the plateau.

Note

This area lies on Whadjuk Noongar Country

Why focus on this WA region?

  • Compact coastal–plain–scarp area from the Indian Ocean to the Yilgarn Craton edge.
  • Strong contrasts in geology, soils, vegetation and hydrology within a single region.
  • Directly relevant to Perth’s water, land use and biodiversity.

Important

A natural laboratory for applying soil–landscape–vegetation concepts locally.

Regional geology: basin meets craton

  • West: Quaternary coastal sediments (dunes, beach sands, wetlands) over the Perth Basin.
  • Centre: Bassendean sands and Guildford clays over Cretaceous basin sediments.
  • East: rocks of the Yilgarn Craton, forming the plateau.
  • The Darling Scarp marks the boundary between basin sediments and craton basement.

Note

Ancient craton + younger basin → contrasts in soils & hydrology

Regional geomorphic units (west → east)

  • Coastal dunes and beaches (Quindalup system).
  • Swan Coastal Plain dune systems – Spearwood and Bassendean.
  • Guildford alluvial plain – river and floodplain deposits.
  • Darling Scarp and Plateau – lateritic uplands over Yilgarn bedrock.

We’ll keep returning to these units.

Coastal dunes and beaches

  • Young, calcareous shoreline and dune deposits close to the Indian Ocean.
  • Very sandy, low nutrient soils; often mobile or recently stabilised.
  • Vegetation: coastal shrublands, foredune grasses, patches of low woodland.

Swan Coastal Plain: Spearwood system

Laliberté et al. (2013)

  • Middle-aged dune ridges with yellow sands over limestone or calcarenite.
  • Soils: deep sands, sometimes with carbonate or hardpan at depth.
  • Vegetation: mixed Banksia woodlands, eucalypts and heaths on better-drained sands.

Swan Coastal Plain: Bassendean system

  • Older, leached dune system with grey, quartz-rich sands.
  • Soils: very deep, acidic, nutrient‑poor sands; often water-repellent.
  • Vegetation: diverse Banksia woodlands and heaths; high biodiversity but low fertility.

Guildford alluvial plain

  • Low-lying plain along major rivers (e.g. Swan, Canning).
  • Soils: duplex and clayey alluvial profiles, often seasonally waterlogged or saline.
  • Vegetation (pre-clearing): riparian woodland, woodlands and shrublands tolerant of wet clays.

Darling Scarp and Plateau

  • Steep escarpment formed along the Darling Fault; uplands on Yilgarn bedrock.
  • Soils: deeply weathered lateritic profiles with gravelly, earthy horizons over granite.
  • Vegetation: jarrah–marri forests, mixed woodlands and shrublands on lateritic and colluvial soils.

Regional soil patterns in the study area

From west to east:

  • Deep quartz sands: coastal, Spearwood, Bassendean – low nutrients, rapid drainage.
  • Duplex and clay soils: Guildford plain – higher fertility, seasonal waterlogging.
  • Gravelly lateritic soils: scarp and plateau – moderate fertility, limited water storage.

Note

Soil texture, depth and chemistry change systematically with geomorphic unit.

Vegetation patterns in the study area

  • Coast and dunes: coastal shrublands and low woodlands.
  • Swan Coastal Plain sands: Banksia woodlands and heaths on deep, well‑drained sands.
  • Alluvial plain: riverine and clay-flat woodlands/shrublands (largely cleared).
  • Scarp and plateau: jarrah–marri forests, lateritic shrublands and granite outcrop communities.

Important

From coast to scarp, vegetation changes track underlying soil texture, depth, organic matter, fertility and water availability along the landscape.

Linking soils, water and vegetation

  • Deep sands → low water-holding, low nutrients → drought‑tolerant, sclerophyll vegetation.
  • Clay and duplex soils → perched water tables, seasonal wetlands, salinity risk.
  • Lateritic gravels → moderate fertility but limited available water; deep‑rooted forest species.

Important

Vegetation patterns encode soil moisture and nutrient regimes across the landscape.

Hydrology across coastal plain and scarp

  • Coastal and dune sands host important unconfined aquifers feeding wetlands and urban water supplies.
  • Groundwater generally flows westward from scarp/plateau towards the Indian Ocean.
  • The scarp forms a boundary between saline craton groundwater and fresher Perth Basin aquifers.

Important

Hydrology links elevation, geology and soils: upland recharge on the plateau, throughflow beneath the plain, and discharge to wetlands, rivers and the coast.

Land use patterns and pressures

  • Coastal plain: dense urban development, infrastructure, horticulture and remnants of Banksia woodland.
  • Guildford plain: agriculture, grazing, urban and industrial land uses on heavier soils.
  • Scarp and plateau: water-supply catchments, forestry, conservation areas, lifestyle properties.

Important

These land uses reshape soils, runoff, recharge and habitat connectivity influencing both ecosystem resilience and management options.

Whadjuk Noongar Country and landscapes

  • Whadjuk Noongar people have managed these coastal and scarp landscapes for thousands of years.
  • Cultural burning, seasonal movement and use of wetlands influenced vegetation patterns and soil properties.
  • Two-way science integrates Indigenous knowledge and Western soil–landscape science for sustainable management.

Important

Country is a living system of land, water, soils, plants, animals and people; understanding landscapes here must include Whadjuk Noongar knowledge and custodianship.

Regional data layers we will use

We’ll explore these data layers in QGIS to understand the landscape e.g.:

  • Digital Elevation Model (DEM)
    • Elevation gradient from ~0–300 m
  • Satellite imagery / vegetation
    • Vegetation cover and land use
    • Banksia woodlands, wetlands, jarrah–marri forests
  • Soil / geology units
    • Coastal sands, alluvial clays, laterites
  • Soil properties (later in unit)
    • Texture, pH, organic C

Activity (10–15 min): Regional observation (on screen or handout)

Goal: recognise major landscape units and their boundaries in the study area.

⓵ Identify and label major landscape units:

  • Coastal dunes and beaches
  • Swan Coastal Plain systems (e.g. Bassendean, Spearwood)
  • Guildford alluvial plain
  • Darling Scarp and uplands

⓶ Mark approximate boundaries between units.

⓷ Note possible processes shaping each unit:

  • Marine/shoreline processes
  • River and floodplain deposition
  • Long-term weathering and erosion of the plateau

We’ll discuss as a group after ~8 minutes.

Discussion: what do you see?

  • Where are the biggest changes in:
    • Elevation?
    • Vegetation cover?
    • Land use?
  • What might these patterns tell us about:
    • Soil types and drainage?
    • Water movement and storage?
    • Landscape stability vs sensitivity?

We’ll link this directly to the QGIS profiles next.

Setting up for activity: QGIS (5 min)

We’ll now use QGIS and Profile Tool to explore the same landscape.

  • If you want to follow along in QGIS:
    • Open QGIS
    • Go to: Plugins → Manage and Install Plugins
    • Search for “Profile Tool”
    • Click Install Plugin

Detailed setup instructions are in the Unit Handout.

QGIS Activity (10-15 min): exploring the Perth–Darling Scarp area

Goal: relate elevation and geomorphic breaks to soil and vegetation changes along one profile.

⓵ Draw a profile line From the Indian Ocean to the Darling Scarp uplands.

⓶ Inspect the profile:

  • Elevation and slope
  • Soil types and properties (pH, texture, organic C)
  • Vegetation types and cover

⓷ Discuss:

  • Where are the steepest slopes and major breaks?
  • How do soils and vegetation shift across these breaks?
  • Where is water likely to accumulate vs drain quickly?
  • Which zones seem most sensitive to disturbance, and why?

Discussion (5 min): what did your profiles show?

  • Elevation and landforms
    • Where do you see clear breaks in slope?
    • How do these breaks line up with the units you mapped earlier?
  • Soil along the profile
    • Where were the coarse-textured soils? Which had more organic C? And did pH vary?
    • How might these differences influence land use or management in each area?
  • Vegetation–soil–topography patterns
    • Where do vegetation types change abruptly along the profile?
    • Are these changes better explained by elevation, slope position, or soil?
  • How might these influence water movement and storage?

Regional processes in this area

Examples of processes at this scale:

  • Long-term weathering and erosion of the inland plateau

  • Uplift and erosion along the Darling Fault, followed by erosion to form the scarp.

  • Marine transgressions/regressions building coastal dunes, shoreline ridges, terraces.

  • River and floodplain deposition forming the Guildford alluvial plains and fans at the foot of the scarp

Important

These long-term processes created the dunes, plains, rivers, scarp and plateau that organise today’s soils, vegetation and hydrology.

Key takeaways

  1. Our study area – from the Swan Coastal Plain to the Darling Scarp on Whadjuk Noongar Country – spans strong gradients in geology, soils, vegetation and water.
  2. Regional units (coastal dunes, coastal plain, Guildford plain, scarp and plateau) give a framework for soil–water–vegetation patterns.
  3. Soil and vegetation contrasts reflect underlying geology, topography and hydrology.
  4. QGIS + Profile Tool let us link elevation to vegetation and inferred soil properties.
  5. This regional understanding underpins later work on soil–water–vegetation relationships.

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