2.2 Soils and Geology 2.3 Topography and Tidal Levels
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783rd Council Meeting 26 November 2019 416 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report 2.2 Soils and Geology According to the Department of Natural Resources and Mines Geological Survey of Queensland: Beenleigh 1:100,000 Series Map the subject site is predominately flood plain alluvium over the Neranleigh-Fernvale Beds formation which consists of a conglomerate of oolitic labile arenite and argillite. Gold Coast Council’s soil mapping indicates the dominant site soils comprise brown and grey kandosols, dermosols and sodosols. The City Plan Acid Sulfate Soils Overlay Map indicates most the site falls within the below 5m Australian Height Datum (AHD) Acid Sulfate Soils Hazard Area (Figure 2.4). Figure 2.4 Acid Sulfate Soils (City Plan V4) 2.3 Topography and Tidal Levels The site is relatively flat with a ridgeline around the existing dwellings where it slopes from an elevation of approximately 10m AHD in a southerly direction towards the Coomera River. The foreshore drops steeply from 2.6m on the high bank to HAT at 1.08m (Figure 2.5). The following semidiurnal tide levels were verified by survey for the subject site: HAT 1.08m AHD MHWS 0.67m AHD MSL 0.11m AHD MLWS -0.43m AHD LAT -0.56m AHD 783rd Council Meeting 26 November 2019 417 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report Figure 2.5 Site Contours (Jensen Bowers 2016) 2.4 Wetlands, Waterways, Drainage and Flooding The site is located within the Coomera River Floodplain. According to the City Plan Flood Overlay Map the majority of the site is subject to flood inundation (Figure 2.6). The City Plan identifies a minor watercourse entering the site in the north-western corner and flowing into the large dam. Another minor watercourse and locally significant wetlands are mapped within the central portion of the site (Figure 2.7). This unnamed watercourse is defined as a watercourse under the Water Act 2000 (based on the Watercourse Identification Map Dataset WM128 Version 11 05.12.2016). 783rd Council Meeting 26 November 2019 418 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report At a site level, stormwater is conveyed southwards from the highest areas of the site towards the waterway in the center of the site as sheetflow and discharges from the site across the eastern boundary. The subject site also contains the following State mapped waterways and coastal hazard areas: Fish habitat areas (Figure 2.8) o QLD Waterways for Waterway Barrier Works – site contains Moderate / Low risk waterway (referral required at OPW stage if works being undertaken within waterway) Coastal protection (Figure 2.9) o Coastal management district; o Coastal hazard area – erosion prone area; o Coastal hazard area – medium storm tide inundation area; and o Coastal hazard area – high storm tide inundation area. Figure 2.6 Flood Overlay Map (City Plan V4) 783rd Council Meeting 26 November 2019 419 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report Figure 2.7 Wetlands and Watercourses Overlay Map (City Plan V4) Figure 2.8 SDAP - Fish Habitat Areas (DILGP, 2018) 783rd Council Meeting 26 November 2019 420 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report Figure 2.9 SDAP – Coastal Protection (DILGP, 2018) 783rd Council Meeting 26 November 2019 421 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report 3. Site Constraints A summary of constraints that may affect management of the site is presented in Table 3.1. Table 3.1 Management Constraints for Subject Site Constraint Present Absent Comments An easement in favour of the Council of the City of Gold Coast for the purposes of Sewerage Treatment Easements and/or restrictions on x (Easements A & B, SP126131) is present adjacent to title the Rail Corridor along the length of the eastern boundary. The Gold Coast City Plan zones the site as Waterfront Zoning provisions x and Marine Industry. Environmental significance mapping for wetlands and watercourses identifies locally significant wetlands as well as major and minor watercourses on the site. Biodiversity, Waterways and State mapping indicates site contains vegetation x Wetlands management waterways (drainline and dam) under the VMA and the drainage line is also mapped as a waterway for the purposes of waterway barrier works under the Queensland Fisheries Act 1994. Bushfire Risk x Does not impact the site City Plan identifies site as part of Waterfront development control area – setback to be advised by Coastal Erosion Hazard x Council. SPP identities site contains erosion prone areas and is subject to storm tide inundation. No nature conservation areas / reserves are present Nature Conservation Areas x on or adjacent to the site. Airport Environs x Does not impact the site No known aboriginal cultural heritage sites are present Aboriginal cultural heritage x on the subject site. * Not listed on City Plan Heritage overlay or State European cultural heritage x Heritage register Majority of site is mapped in ‘below 5 m AHD’ hazard Acid sulfate soils - risk x category in City Plan. Flood prone x The site is mapped as being affected by flooding. Small area of ‘Moderate’ hazard identified on City Plan Landslide Hazard and Steep Land x around the existing dwelling. Tree Preservation Order x Does not impact the site No State regulated vegetation is mapped on the site. Mapped Vegetation x No native vegetation is mapped as occurring on site under the City Plan Vegetation Management Overlay. Mapped Essential Habitat x No Essential Habitat is mapped on the site. No threatened species observed on-site during the Observed threatened species x Ecological Assessment. SPRP Koala Assessable x Does not impact the site Development Area *All staff will be inducted into aspects of aboriginal culture that may arise on the site such as discovery or unearthing of artefacts/midden sites. Staff will be advised that if objects are found on site, work must immediately cease the Council notified. Work will not continue until permission is granted by Council. 783rd Council Meeting 26 November 2019 422 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report 4. Development Summary The structure plan for the proposed development comprises medium density residential precincts, a neighbourhood centre zone and approximately 34.3ha of public open space (Figure 4.1). The open space comprises a mix of 5.9ha of local district park nodes and 28.4ha of open space reserve areas including the Coomera River foreshore and a 24ha coastal wetland. Figure 4.1 Landscape Masterplan (Place Design Group, 2018) 783rd Council Meeting 26 November 2019 423 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report 5. Ecological Assessment Summary A site investigation was undertaken in April 2017 by Burchills Engineering Solutions. The following summarises the results of these surveys. 5.1.1 Flora A total of 103 species of flora were identified within the site, comprising 63 native species and 40 non-native species including six (6) species listed as Restricted Invasive Plants under the Queensland Biosecurity Act 2014. Six (6) distinct vegetation units were identified on the site (Figure 5.2). These were classified as: Vegetation Unit A – Anthropogenic Grassland with Isolated Canopy Trees Vegetation Unit B – Swamp Oak and Mangrove Fringing Forest (RE 12.1.3) Vegetation Unit C – Slash pine plantation Vegetation Unit D – Dams with fringing sedgeland Vegetation Unit E – Gardens with mature feature trees Vegetation Unit F – Sugar cane plantation with agricultural drains The constructed drainage line through the centre of the site is tidal and the banks of the drain are subject to tidal inundation. These areas (between MSL and MHWS) contain plants considered ‘marine plants’ under the provisions of the Fisheries Act 1994. Figure 5.1 Tidal drain through centre of site As a result of tidal exchange, salt couch (Paspalum vaginatum) has established on the banks of the drain. Some swamp oak (Casuarina glauca) juvenile regrowth occurs sporadically along the channel with increasing prevalence at the eastern extent where the channel forms a small pool / lagoon. Two 783rd Council Meeting 26 November 2019 424 Economy, Planning & Environment Meeting 20 November 2019 Adopted Report (2) 50-100cm high Grey mangrove (Avicennia marina) saplings were recorded on the banks of the lagoon as well as occasional clumps of Mangrove clubrush (Schoenoplectus littoralis). Vegetation along the banks of the channel is, however, dominated by exotic grasses and forbs including Johnson grass, Rhodes grass, Common couch, Curled dock, Fat hen and other exotic weeds. At the western extent the channel widens into a soak with stands of predominantly exotic grasses and forbs with some freshwater native wetland species also present including Common reed (Phragmites australis), Juncus usitatus, Persicaria spp. and Bulrush (Typha orientalis). A more mature and diverse marine plant community occurs along the banks of the Coomera River. The vegetation along the river is ecotonal and grades from remnant mangroves on the lower bank (below HAT) to Qld blue gum woodland on the higher bank. Marine plants in this community include Grey mangrove (Avicennia marina), River mangrove (Aegiceras corniculatum), Swamp oak, Native hibiscus (Hibiscus tiliaceus), Milky mangrove (Excoecaria agallocha), Salt couch, Sand couch (Sporobolus virginicus), Seablite (Suaeda australis) and Native spinach (Figure 5.3). 5.1.2 Fauna Fifty-eight (58) species of fauna