Semi-arid Western Australia Research Articles

Wanderrie Banks: Micro-Relief Patterns in Semiarid Western Australia

Wanderrie country consists of alternate sand banks and alluvial flats, termed wanderrie banks and flats, developed on tributary alluvial plains in semiarid Western Australia. The origin of wanderrie features is sought by investigation of their patterns, profiles, surface deposits, and geomorphic setting. Three types of wanderrie pattern are shown to depend on relationships between drainage direction and northwest and southeast winds which appear to have been of dominant and subdominant status in a former arid period of stronger eolian activity: a pattern transverse to northwest drainage; a longitudinal pattern parallel with cross streams, and hence mainly at right angles to northwest winds; and an intermediate oblique pattern. A fourth, diffuse pattern occurs on shorter slopes, particularly those drained obliquely to the northwest winds. Wanderrie banks are 2–4 feet high and occupy steeper sectors on stepped slopes; their crest forms show displacement by easterly winds. Their soils are sands with textures and grading similar to those of eolian sands in the same area; the flat soils are alluvial earths with fairly high silt and clay content. Wanderrie features are restricted to the margin of the plateau of Western Australia, where surface drainage persisted during the arid period; in areas of poorly organized drainage further inland they are replaced by sand-plain. Wanderrie features are attributed to the combined action of wind and sheet-flow. Longitudinal banks originated as sand-precipitation ridges in lee of water lanes; transverse banks grew from wind sorting in steeper accumulation zones on stepped slopes subject to sheet-flow. Subsequent modification of bank form indicates a dominance of easterly winds, consistent with the present wind regime.