Location map showing coverage of Calwynyardah land system defined by black region.
State land type: Alluvial plains with mixed woodlands/shrublands and mixed grasses.
Geology: Quaternary alluvium; weathered gently folded sandstone and shale of Permian and Triassic age.
Geomorphology: Alluvial plains - tributary alluvial plains: up to 19km in extent, comprising loamy alluvial plains with extensive scalded areas and minor sandplain islands, occurring downslope from restricted laterised summit remnants; sparse pattern of subparallel alluvial drainage floors.
Land management: Scalded tracts and drainage floors (units 4 & 6) of the system have moderate to high susceptibility to erosion if vegetation cover is lost; control of grazing pressure is essential.
Image of alluvial plains supporting grassy woodlands of beefwood (Grevillea striata) and acacias. Photo: DAFWA
Stylised block diagram showing location of land units for the Calwynyardah land system (numbers on diagram represent land units in table below)
Table of Calwynyardah land system – land units. * Numbers in brackets refer to soil family or vegetation community/alliance in ‘General report on lands of the West Kimberley area, WA’ (Speck et al. 1970); + Pasture types described in Appendix 1; Note: Proportions and occurrence of pasture types within land units are subject to change over time due to invasion by native and introduced species, seasonal conditions, fire frequency and grazing management.
Summit remnants: up to 15m high; sandy slopes less than 0.3%, but up to 7% adjacent to breakaways, with local exposures of laterite and weathered rock; delimited by breakaways up to 12m high or by stony slopes up to 2%.
Reddish loamy soils: Tippera family (2). Laterite exposures in and marginal to breakaways.
Mainly spinifex grassland with scattered trees and shrubs. Triodia intermedia community (57); locally 54 and 16.
Lower slopes:concave up to 3% and less than 1.6km long, forming gently rounded spurs up to 1.5m high and 400m wide with marginal slopes less than 1%; colluvial mantles and local outcrop.
Complex association of reddish sandy and loamy soils; Tippera family (2); and brownish loams over red clay: Moonah family (17).
Spinifex grassland and low beefwood woodland. Triodia intermedia community (57) andGrevillea striata alliance (34b and 34c).
Alluvial plains: up to 3.2km in extent with gradients 1 in 200 to 2 in 500; lightly sealed sandy surfaces with pebble patches.
Yellowish sandy soils with laterite gravel horizon: Tableland family (5).
Low beefwood woodland with Triodia bitextura, Chrysopogon spp., and Triodia pungens. Grevillea striata alliance (34a, 34b, 34c).
Scalded tracts:extending up to 6.4km downslope, gradients 1 in 150; lightly sealed sandy surfaces with pebble patches.
Association of greyish to brownish sands and loams over tough domed clays: Jurgurra family (19) with yellowish sandy to loamy soils: Elliott family (6).
Much bare ground; patches of beefwood and Bauhinia woodlands with Triodia bitextura, Grevillea striata alliance (34b and 34c).
Sandplain islands:up to 1.6km wide with slopes up to 2%.
Deep red sands: Cockatoo family (7).
Woodland with prominent Acacia tall shrub layer and Triodia bitextura, Chrysopogon spp. ground storey. Corymbia dichromophloia alliance (10, 11) and 56.
Drainage floors:up to 400m wide, gradients 1 in 100 to 1 in 500; locally with channels up to 6m wide and 1.2m deep.
Brownish sands and loams over red clay: Moonah family (17). Minor occurrence of reddish sandy soils: Yabbagoddy family (1).