Summary - City of Gosnells

Regional Setting 7mapped as clayey sand of the Guildford Formation (Sc). In the lower catchment of Yule Brook, southwest ofBrixton St (and below about 7m AHD) the clayey sand (Sc) was mapped as grading into GuildfordFormation sandy clay (Cs). The same sandy clay (Cs) was also mapped over much of the MKSEA in the areasouth of Victoria Rd (in the lower catchment of Bickley Brook). [Note the term ‘mud’, as defined in Section3.3 below, is equivalent to the term ‘clay’ as used in Jordan (1986).]The Deep Bassendean Sands (S8) unit is mapped by Jordan (1986) as prevalent in the east of the MKSEA.However, the Guildford Formation underlying this area was evident in several areas where sandy clay (S10)was exposed in slightly lower lying areas amongst the dunes. The dune sands (S8) extended to the yellowsand of the Ridge Hill Shelf (S12) at an elevation of about 26 m AHD at the eastern boundary of theMKSEA, south of Victoria Rd. Apart from these dunes in the east of the MKSEA, there was a roughlycircular, quartz sand dune (S8) at the corner of Bickley and Victoria Rds and two low, linear sand ridges (S8)in the centre of the Greater Brixton Street Wetlands between Brook and Boundary Rds.A small basin of peaty sand (Sp1) was mapped by Jordan (1986) at the base of one of the low sand ridges atthe corner of Boundary and Bickley Rds. Peaty sediments were not recorded elsewhere in the MKSEA or theGreater Brixton Street Wetlands (Jordan, 1986; V & C Semeniuk Research Group, 2001). This occurrencewas, therefore, unusual for this area.The MKSEA and BFS 387 are located in an alluvial fan complex (V & C Semeniuk Research Group, 2001).This is evident in the topography of the area; it is a series of flat to gently undulating alluvial terraces(floodplains and palusplains) that gently grade down to the Canning River and are dissected by Yule Brookand its tributaries (Figure 7). The regional stratigraphy in this system is linked to the geographic position inthe landscape (V & C Semeniuk Research Group, 2001) as the structure of the alluvial fan has been createdby the gradation from a large to small sedimentary load and gradation from coarse to fine sediments withincreasing distance from the Darling Scarp. This gradation can be seen superficially in the soils (Jordan,1986) (Figure 6) where the finest soils (Cs) of the area are distributed in the downslope, western areas ofBFS 387. The stratigraphic style of the various zones of the alluvial fan also has implications with regard tothe characteristic hydrological processes that operate in each of these zones along this gradient (V. Semeniukpers. comm.). The variation in habitat in the BFS 387 and the MKSEA (topography, soils, stratigraphy andhydrology) is reflected in the subtle variation in vegetation assemblages that have been noted as occurringalong the topographical gradient from east to west in the Greater Brixton Street Wetlands (Goble-Garratt,1991). Thus, the alluvial fan complex can be seen as a series of habitat zones created by the variation in thephysical environment along the topographical gradient (Figures 6, 7). The habitat zones created by thevariation in the physical environment along the topographical gradient of the alluvial fan complex in WattleGrove-Kenwick-Maddington are important features that underlie the resilience, connectivity andsustainability of the biodiversity values in the area and should be considered with regard to the conservationvalues and the management opportunities in the area.Table 2.2: Soils of the MKSEA (adapted from Jordan, 1986)Soil unit Descriptors applicable to soil unit LandformSand over sandy clay(Qpb/Qpa: S10)Shallow (Pleistocene) Bassendean Sands overPleistocene alluvium of the Guildford FormationPalusplain (Pinjarra Plain) at 10-14 m AHDapprox.Sandy silt (Qha: Ms4) Holocene alluvium Valley floor of Yule BrookClayey sand (Qpa: Sc)Sandy clay (Qpa: Cs)Deep BassendeanSands (Qpb: S8)Sand (Qpr: S12)Pleistocene alluvium of the Guildford FormationPleistocene alluvium of the Guildford FormationDeep (Pleistocene) Bassendean SandsStructure-less yellow sands of the YoganupFormationPalusplain-floodplain (Pinjarra Plain)