Phase 1 ( LRP17-1001 Commonly referred to as Phase 1 of Trial Site One - CSIRO monitoring )
The first of LDC large scale sites , Mt Wickham is Phase 1 is an alluvial gully complex on chromosol soils . With a gully treatment area of 4.23ha and a further 12ha of catchment feeding into the gully ( Figure 10 ), the site is characterised by linear hillslope gullies , scalds , and major alluvial gullies , including tunnel erosion on highly sodic soils that drain into Sandalwood Creek and then into the Bowen River .
Ecological engineering firms Verterra and Alluvium were contracted to design the gully remediation technical design and manage the construction . They collected data in the field to inform the design , including soil sampling and electromagnetic soil ( EM ) mapping . EM sends signals into the soil and measures moisture , texture , and salinity to help determine catchment treatment zones . Local contractors and machinery supported the on-ground works . Earthworks and initial ground works were carried out in October and November 2018 .
The main areas of Phase 1 works are shown in Figure 10 . Phase 1 consisted of :
● grade control rock chutes
● re-contouring of the rehabilitation area
● soil amelioration using a range of chemical treatments , and
● revegetation using a range of pasture and legume species .
○ 400 tonnes of topsoil were removed and stockpiled
○ 100 tonnes of gypsum and 374 tonnes of compost were blended with stockpiled topsoil for final dressing
○ 40 round hay bales ( sorghum hay ) were rolled out manually at distances of 20-30m
○ Hay bales were placed in rows across the basin to slow water and add organic matter
○ 538kg seed planted , including deep-rooted legumes , canopy species , pasture grasses , legumes and cover crops .
Figure 10 . Image of the site showing the areas of Phase 1 works at Mt Wickham . Image taken in February 2019 following a rainfall event ( photo credit : Damon Telfer ). Source : NQ Dry Tropics .
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