Summary - City of Gosnells

Wetlands Field Survey 89Some wetlands in the MKSEA were more modified than the CCW above with regard to wetland vegetationand other wetland attributes and processes. These wetlands were palusplains, sumplands, damplands andcreeks of the Pinjarra Plain and thus scarce wetland types. Some of these wetlands retain open to scatterednative vegetation canopy species and/or were important to the maintenance of wetland values and processes(e.g. biodiversity, groundwater quality and quantity) of adjoining CCW and of the Swan Canning Riversystem. The modification that these wetlands have been subject was considered as capable of beingremediated by re-vegetation and by the application of best practice water sensitive design and catchmentmanagement principles in the overall plan for the area.In accord with the above, part of UFI 7645, UFI 7783 and part of UFI 8047 (that are currently MUWs inDEC, 2008a) were assigned the management category of REW in the current survey (Table 6.3; Figure 11).Parts of UFI 13362 adjacent to Yule Brook (that are currently MUW) were also recommended for REWstatus in this study, as part of the proposed amelioration of the hydrological regime in BFS 387 and theMKSEA, the restoration of the former Yule Brook floodplain and to enable catchment managementobjectives with regard to the Swan-Canning River Water Quality Improvement Plan as listed by GHD(2008).One of the areas in UFI 13362 where existing wetland values can be enhanced to meet the objectives aboveis the least altered area of UFI 13362 with regard to soil, landforms and hydrology. Floodplains of this type(that have not had not been built upon and have their geomorphic integrity and hydrology remaining more orless unaltered are scarce wetland types of the Pinjarra Plain (more than 94% of wetlands of the Pinjarra Plainhave been developed or degraded, Hill et al.,1994). The paddocks of this large area are currently sparselystocked and there are few buildings. There is a small creek that traverses UFI 13362 before entering thethickly vegetated, natural area of UFI 7635 (which is recommended as a CCW in the current survey) andflowing into Yule Brook. This creek retains its natural course for much of its length as it traverses thepaddocks and the area around its confluence with Yule Brook (at UFI 7635). This area is the least disturbedarea of floodplain vegetation adjacent to Yule Brook. The Yule Brook floodplain and creek in Lot 2008 canbe enhanced by the regulation of land uses to avoid further modification, control of weeds, revegetation toincrease infiltration of rainfall and surface water into groundwater and appropriate re-design of the MUW atthe head of the tributary (UFI 7632) to improve water quality. The tributary can then function to recharge thefloodplain as well as to provide drainage to developed land to the east.In general, the remainder of the wetlands in the MKSEA had either been excavated to form dams and drains,or had been severely eroded by the intensive grazing of stock or they had been totally or partially filled. Theywere usually totally cleared of native vegetation. These wetlands were assigned the management category ofMUW. Such wetlands are the only category of wetland that can be modified for use in storm water run-offtreatment and, if appropriately designed and engineered, such facilities could contribute to supporting thewetland attributes and functions of nearby CCW and REW wetlands in the MKSEA (as above for REW13362). These wetlands are often located in areas adjacent to CCW and REW and should be reserved asbuffer zones for them (Figures 11, 12). Land uses in wetlands in this category (particularly around BFS 387and the CCWs and REWs of Precinct 2) should be regulated to exclude any additional activities that mayimpact negatively on water quality and quantity of the adjacent CCW and REW and of the Swan CanningRiver system. Revegetation should be a major objective for the MUW of the MKSEA.The management categories that were assigned to wetlands in the current survey are listed in full (incomparison with the corresponding categories in the Swan Coastal Plain Wetlands Dataset) in Table 6.3below.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