University of Wollongong Thesis Collections University of Wollongong Thesis Collection University of Wollongong Year Mangrove and saltmarsh surface elevation dynamics in relation to environmental variables in Southeastern Australia| Kerrylee Rogers University of Wollongong Rogers, Kerrylee, Mangrove and saltmarsh surface elevation dynamics in relation to environ- mental variables in Southeastern Australia, PhD, School of Earth Environmental Sciences, University of Wollongong, 2004. http://ro.uow.edu.au/theses/653 This paper is posted at Research Online. http://ro.uow.edu.au/theses/653 NOTE This online version of the thesis may have different page formatting and pagination from the paper copy held in the University of Wollongong Library. UNIVERSITY OF WOLLONGONG COPYRIGHT WARNING You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: Copyright owners are entitled to take legal action against persons who infringe their copyright. A reproduction of material that is protected by copyright may be a copyright infringement. A court may impose penalties and award damages in relation to offences and infringements relating to copyright material. Higher penalties may apply, and higher damages may be awarded, for offences and infringements involving the conversion of material into digital or electronic form. Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting CHAPTER TWO THE SETTING 2.1 Introduction This study focuses on saline coastal wetlands within Southeastern Australia. This includes mangrove and saltmarsh habitats geographically distributed between the NSW-Queensland border and coastal Victoria. Study sites were selected according to criteria detailed in this chapter. Study site descriptions are provided, with particular reference to factors that may influence mangrove and saltmarsh distribution and surface elevation dynamics, such as climate and sea-level rise. 2.2 Site Selection Criteria Sites were selected on the basis of four criteria. Since the observed trend of mangrove encroachment of saltmarsh (Saintilan and Williams 1999, 2000) is largely limited to Southeastern Australia, sites were selected from a number of regions throughout temperate Southeastern Australia. Study sites covered 7 catchments and 12 individual locations and approximately 1 800 km of coastline (Figure 2.1 Table 2.1). Secondly, sites were included from a number of representative geomorphic settings, as described by Roy et al. (2001) (Table 2.1). These settings incorporate geological properties, morphology, and environmental factors such as salinity and sediments to express their structure and function and aid coastal management. Five main estuary groups were recognised; bays (I), tide-dominated estuaries (II), wave-dominated estuaries (III), intermittent estuaries (IV) and freshwater bodies (V). Since mangrove and saltmarsh vegetation generally occur abundantly in tide-dominated estuaries and wave-dominated estuaries, these estuary types have been included in this study. While bays in New South Wales do not tend to support large areas of mangrove and Kerrylee Rogers 19 Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting saltmarsh, primarily due to the wave-activity on the eastern coastline, bays in Victoria experience less wave-activity and support mangrove habitats that are among the most productive communities of coastal Victoria (Champion 1974) and diverse saltmarsh habitats (Adam 1990). Therefore, four sites in Western Port Bay have been included to represent the bay estuary group. In addition, Roy et al. (2001) identified 13 estuary types, with ocean embayments (1), drowned valley estuaries (3) and barrier estuaries (5) specifically represented in this study. Estuary type, along with stage of infilling and development impacts are all considered to be important modifiers of estuarine ecology. It is anticipated that this classification will aid comparisons between estuaries. Sites were also chosen on the basis of the degree of interest and involvement of local management agencies. It was anticipated that this research would provide information to catchment, estuary and coastal management committees, government agencies and coastcare groups relevant to the management of mangrove and saltmarsh communities. In particular, Western Port Bay, Hawkesbury River, Homebush Bay and Minnamurra River have been included because of enthusiastic support from local management groups. Finally, where possible, sites of international, national or state significance have been selected. Kooragang Island is a RAMSAR listed wetland. The wetlands of Currambene Creek, Cararma Inlet and French Island are located in marine parks and are protected under the NSW Marine Parks Act (1997) and the Victorian National Parks (Marine National Parks and Marine Sanctuaries) Act (2002). The wetlands at Rhyll are administered under the Philip Island Nature Park and the wetlands of Quail Island are classified as a Nature Conservation Reserve and protected under the Victorian Crown Land (Reserves) Act (1978). Homebush Bay, lies within the jurisdiction of Sydney Olympic Park Authority and protected under the NSW Sydney Olympic Park Authority Act (2001), thereby having specific planning policies that detail their management and conservation. Ukerebagh Island, Kooragang Island, Minnamurra River, Currambene Creek and Cararma Creek are designated SEPP 14 wetlands under the NSW Environmental Planning and Protection Act (1979). Kerrylee Rogers 20 Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting Figure 2.1: Locality map of study sites. Table 2.1: Study sites, their geomorphic setting and significance. * From Roy et al. 2001. Kerrylee Rogers 21 Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting 2.3 Site Descriptions 2.3.1 Ukerebagh Island, Tweed River Ukerebagh Island is located on the Tweed River, near the border of NSW and Queensland, some 860 km north of Sydney (153o33’E, 28o10’S, Figure 2.2). The main arm of the Tweed River is approximately 60 km long and the tidal limit is located 2 km upstream from Murwillumbah (DIPNR 2004). The Tweed River system, incorporates the Tweed River channel, Terranora Creek, Bilambil Creek, Rous River, Terranora Broadwater and Cobaki Broadwater. Ukerebagh Island is located approximately 1.5 km south of the Tweed River entrance and is enclosed by Terranora Inlet, the Tweed River channel and Ukerebagh Passage. The Tweed River catchment (1 114 km2) lies primarily on alluvial flood plains. The catchment is surrounded by the Tertiary aged McPherson Range and Lamington Plateau, consisting primarily of volcanics (GA 2004). The Tweed River catchment exhibits sub-tropical climate characteristics, with mean maximum daily temperatures at nearby Murwillumbah of 29.6oC and mean daily minimum temperatures of 8.5oC. Mean monthly rainfall ranges between 40.5 mm and 230.9 mm, with rainfall being significantly high in the warmer months of November to May (BOM 2004a). All catchments within the study, including the Tweed River, are subject to the effects of El Niño and La Niña cycles (BOM 2004b). The Southern Oscillation Index (SOI) is used to indicate El Niño episodes. Negative SOI values are typically accompanied by warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade winds and a reduction in rainfall over eastern and northern Australia. The last El Niño event occurred in March 1997 to April 1998 (Figure 2.3). The SOI was negative during the study period, commencing in March 2002, with positive values being evident in December 2003 (BOM 2004b). Kerrylee Rogers 22 Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting Figure 2.2: Location of the Tweed River and Ukerebagh Island. Kerrylee Rogers 23 Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting Figure 2.3: Southern Oscillation Index (SOI) since January 1995. Note the negative values since March 2002 (BOM 2004b). Since March 2002 to November 2003, rainfall averaged approximately 30% less than mean monthly rainfall (Figure 2.4) at Murwillumbah. Some months, such as July 2002, exhibit an almost absence of rainfall (BOM 2004c). Figure 2.4: Total monthly precipitation, and 5-month mean precipitation since January 2000 and monthly average precipitation since 1972 recorded at Murwillumbah weather station (BOM 2004c). Kerrylee Rogers 24 Mangrove and Saltmarsh Surface Elevation Dynamics in Chapter Two: Relation to Environmental Variables in Southeastern Australia The Setting The Tweed River has undergone a number of morphological changes that have been focussed in the estuarine regions. The most significant changes include training of the river entrance, dredging of the river and its tributaries and the Tweed River Sand Bypass Project. Dredging of the Tweed River began in the 1870’s and the river entrance was trained in 1904.