Morphological Development of Coastal Dunes in a Humid Tropical Environment, Cape Bedford and Cape Flattery, North Queensland by Kenneth Pye (1982)
I found this research paper that was helpful in explaining the origins of the development of the dunes. This paper examines coastal sand dunes in a tropical environment in North Queensland, Australia - specifically at Cape Bedford and Cape Flattery, about 50km north of Cooktown. Here's what the research reveals:
What Makes This Study Unique
Coastal sand dunes are typically rare in humid tropical climates because high rainfall and vegetation usually prevent their formation. However, this area has developed some of Australia's largest coastal dune systems despite receiving over 1,700mm of rain annually.
The Dune System
Scale and Size: The dunefield covers more than 500 square kilometers, with some individual dunes reaching:
Over 4km in length
Up to 1km wide
Heights of 80+ meters
Sand extending up to 20km inland from the coast
Types of Dunes Found:
Parabolic dunes - U-shaped dunes that form from localized "blowouts" in vegetation
Elongate parabolic dunes - Long, hairpin-shaped dunes that can stretch for kilometers
Crescent-shaped dunes (lunettes) - Small crescents that form downwind of lakes
Degraded dune areas - Older, weathered dunes now covered by vegetation
Why These Dunes Exist
Several factors combine to create this unusual tropical dune system:
Abundant Sand Supply: The surrounding landscape contains extensive sandstone formations and granites that weather to produce large quantities of quartz sand.
Strong, Consistent Winds: The area experiences powerful southeasterly trade winds, especially during the dry season (May-November), with about 99% of sand-moving wind energy coming from the southeast.
Seasonal Climate: While the area is tropical, it has a distinct dry season when vegetation stress and lower rainfall allow sand movement to occur.
Exposed Coastal Location: The headlands of Cape Bedford and Cape Flattery are directly exposed to the prevailing winds.
Dune Formation and Movement
Most dunes begin as "spot blowouts" - areas where vegetation is destroyed by fire, cyclones, or drought, creating bare patches that wind can erode. Once started, these expand into larger dune systems.
Movement Rates: The study found that active dunes move relatively slowly:
Maximum recorded rate: 5.6 meters per year
Most dunes move less than 2 meters per year
Many dunes are now completely stabilized by vegetation
Environmental History
The research suggests these dunes formed during earlier periods when conditions were more favorable for sand movement - possibly during drier phases of the Holocene (last 10,000 years) or Pleistocene ice ages. Radiocarbon dating of buried organic material indicates some dune activity occurred at least 5,000-6,000 years ago.
Current Status
Today, most of the dunes are stabilized by vegetation, primarily drought-resistant species like Acacia, Melaleuca, and Casuarina. Only about 10% of dunes remain actively moving, and there's limited new sand supply from beaches.
Significance
This study demonstrates that large coastal dune systems can develop and persist in humid tropical environments under the right combination of geological, climatic, and geographic conditions. It challenges the conventional wisdom that such features are restricted to arid or temperate regions.
The research also provides insights into how past climate changes affected landscape development in tropical Australia and helps us understand the complex relationships between vegetation, climate, and landform evolution.