Summary - City of Gosnells

Wetlands Field Survey 78The stratigraphic sequences (that underlie the superficial sediments that were mapped simply by Jordan in1986 as S10, Cs and Sc) were found to be complex and varied. Also many factors (groundwater, artesianflow, subsurface seepage etc) apart from rainfall were found to contribute to the recharge and discharge ofwetlands in this area (VCSRG, 2001). Thus in some areas of the dunes, (e.g. in the University of WesternAustralia Allison Baird Flora Reserve), the seasonal waterlogging was found to extend over part of theslopes of dunes and to form paluslopes (seasonally waterlogged slopes). Floodplains (seasonally inundatedflats) were also found to be present adjacent to the dunes. The paluslopes and floodplains described in BFS387 in VCSRG (2001) have not, as yet, been incorporated into the SCP Wetland Dataset. Paluslope wetlandsare uncommon in south west Western Australia. Paluslopes have not been characterised in any other areas ofthe SCP. Floodplains with intact native vegetation are also very uncommon on the SCP as most of thesewetlands have been cleared for agriculture or highly modified by drainage works. Both paluslopes andfloodplains are represented by areas of intact native vegetation in BFS 387; these wetlands are of highconservation significance.The primary task of the current survey was to characterise the conservation values in the MKSEA. As intactnative vegetation is usually a good proxy for high conservation values on the eastern SCP, the current surveyfocussed primarily on all of the areas of remnant native vegetation in the MKSEA that could be classed as‘native bushland’ according to Government of Western Australia (2000). Each area of native bushland wasexamined in the reconnaissance survey and most were later sampled in the site-based flora and vegetationstudy. Many of the sampled sites were also investigated with regard to stratigraphy and hydrology to verifywetland status in the manner recommended by DEC (2007). This approach captured all of the highconservation value wetlands in the MKSEA that are currently assessed as CCW and or REW (DEC, 2008). Italso enabled the recognition of some additional wetlands, some wetland types and wetland processes in theMKSEA that are of high conservation value and that were not previously known from Government ofWestern Australia (2000) or the SCP Wetlands Dataset (DEC, 2008).The current survey was not intended as a fine scale mapping of the wetland boundaries and a definitiveassessment of the management categories of wetlands (in order to submit a case for changes to the SCPWetlands Dataset DEC or to develop a plan to manage the important wetlands of the area for conservation)but as an overview that reliably identified areas of the highest conservation significance/ecologicalsensitivity and priorities for further investigation. Similarly, the water monitoring currently commissionedby the City of Gosnells (where the sampling of water levels has been confined to a small number ofpiezometers spread over a large area) will not be sufficiently intensive to adequately characterise thewetlands of the area to the standard required prior to rezoning and development proposals according to DEC(2007). Due to the complicated stratigraphy, hydrology and biology of the area, further fine-scale wetlandstudies at a scale and intensity similar to VCSRG (2001) should be carried out to map the main wetlandboundaries more accurately and to investigate and analyse the processes that maintain the wetlands. Thisadditional wetland mapping and assessment should be carried out at a scale that will take into account theeffect of the drainage measures that are installed on individual landholding blocks in the MKSEA. Implicit insuch a study would be an examination of the stratigraphy and hydrology at a scale appropriate to habitatvariables that determine native vegetation. It would be most appropriate to carry out such further wetlandswork as part of the development of an integrated management plan for remediating the hydrological cycle inthe area and the sustainable management of the water resources of Yule Brook, BFS 387, BFS 53 and areasof high conservation significance in the MKSEA.The wetlands identified and delineated in the current survey, the geomorphic classification and themanagement category determined for each wetland are presented below in Sections 6.1, 6.2 and 6.3respectively.Tauss, C. and Weston, A.S. (2010). The flora, vegetation and wetlands of the Maddington-Kenwick Strategic Employment Area.A survey of the rural lands in the vicinity of the Greater Brixton Street Wetlands. Report to the City of Gosnells, W.A. Version 18.04.10