A Spatio-Temporal Assessment of Landcover and Coastal Changes at Wandandian Delta System, Southeastern Australia

Journal of Marine Science and Engineering

Article A Spatio-Temporal Assessment of Landcover and Coastal Changes at Wandandian Delta System, Southeastern Australia

Ali K. M. Al-Nasrawi 1, Carl A. Hopley 1,2, Sarah M. Hamylton 1 and Brian G. Jones 1,* ID

1 School of Earth and Environmental Sciences, University of Wollongong, Wollongong NSW 2522, Australia; [email protected] (A.K.M.A.); [email protected] (C.A.H.); [email protected] (S.M.H.) 2 Buildings & Facilities Sustainability, Wollongong City Council, Wollongong NSW 2522, Australia * Correspondence: [email protected]; Tel.: +61-2-42213803

Received: 21 September 2017; Accepted: 17 November 2017; Published: 27 November 2017

Abstract: Large numbers of people live along and depend upon the world’s coastal resources. Human modifications of the coastal zone, in combination with climate induced environmental changes, have had a major effect on the natural ecological systems. GIS analysis of remote sensed data, combined with fieldwork and laboratory tests, can be used to determine the resultant eco-geomorphic changes that need to be managed sustainably on a worldwide scale. Modelling the eco-geomorphic dynamics between 1949 and 2016 on the Wandandian Creek delta (southeastern NSW, Australia) provides a case study of management options for such coastal resources. Results from the Wandandian Creek delta show that sand/silt sediment derived from the partially (22%) modified terrestrial catchment has prograded into the wave-dominated St. Georges Basin where it is impacted by nearshore processes. Clear spatio-temporal growth of the areal extent and elevation of the deltaic levees and sandspits, with their associated mangroves and saltmarshes, has occurred over the past 65 years. Although the growth rate has fluctuated during the study period, due to flood events in 1974, 1990s and 2010, the overall subaerial and subaqueous delta area has had an average growth of 4168 m2 annually with the shoreline extending 1.451 m/year on average. This geomorphic growth has stabilised the estuarine deltaic habitats with high proportions of nutrients and organic matter, particularly within saltmarsh, mangrove, Casuarina/Juncus and other mixed native plant areas. This research shows the importance of analysing morphological changes observed on the delta that can be related to both anthropogenic modifications and natural processes to the catchment and thus should be used in the development of catchment and coastal management plans.

Keywords: anthropogenic modiﬁcations; eco-geomorphology; remote sensing; GIS-modelling; sediment progradation

1. Introduction Many coastal ecosystem management strategies have become more focused on the conservation and sustainability of coastal wetlands [1,2] locally [3], regionally [4] and globally [5] according to their unique ecosystem function roles [6]. However, they are located in sensitive zones where anthropogenic and climate change stressors are concentrated, such as estuaries and deltaic platforms [7–9]. For effective management of such areas it is imperative that comprehensive knowledge of their environmental responses to current anthropogenic and climatic stressors is known, along with the factors that have driven such responses within the last few decades, to enable prediction of their future behaviour.

J. Mar. Sci. Eng. 2017, 5, 55; doi:10.3390/jmse5040055 www.mdpi.com/journal/jmse J. Mar. Sci. Eng. 2017, 5, 55 2 of 21

One of the most cost effective methods of studying changes in coastal ecosystems is through global information system (GIS) analysis of aerial photograph and satellite images [3,4,10,11]. Ozesmi and Bauer [10] provided an overview of the most appropriate satellite data and classification methods to use for studying wetlands. They also discussed how complimentary information could be obtained from aerial photographs, thus providing the opportunity to extend equivalent analyses back before satellite data became available to study longer term changes to wetland composition and shoreline positions. Some studies have relied entirely on satellite data, such as the study by Cho et al. [11] who successfully mapped wetland and shoreline changes on a broad scale in southeastern India. The same techniques have been applied when mapping vegetation and shoreline changes in inland wetland situations, such as Haack’s [12] study of the distribution and dynamic nature of small isolated wetlands in the plains and highlands of Kenya and Tanzania, and Roshier and Rumbachs’ [13] mapping of temporary wetlands in the arid areas of the Darling River basin in eastern Australia. The success of these studies led us to instigate a case study modelling the current and historic coastal ecosystem dynamics on the Wandandian Delta (St. Georges Basin, Southeastern Australia) as a method for providing data to assist in developing local catchment and coastal management plans. The aim of this study is to use the Wandandian Delta as a case study to monitor and measure sensitive shoreline, land cover and vegetation changes in a deltaic system and its associated coastal wetland in order to assess potential options for conserving and managing the wetlands. This study (i) employs spatial technologies to determine the ecological and geomorphological (eco-geomorphic) growth of the estuarine system within the last few decades, (ii) considers the direct and indirect influences of anthropogenic and environmental trends on the catchment runoff and sedimentation factors, (iii) assesses the historical eco-geomorphic trends to determine the main factors likely to affect the future ecosystem health, and then (iv) indicates how these findings could be extended to other estuarine deltaic regimes and important coastal wetlands worldwide. This work is relevant to management because it indicates how susceptible the estuary is to shoreline expansion or contraction, which causes changes in ecosystem accommodation space as a function of sediment transport and deposition from the catchment.

2. Background

2.1. The Study Site Specifications The Wandandian deltaic eco-geomorphic system is located on the southeastern coast of New South Wales (35◦06023.400 S 150◦33020.500 E), about 194 km south of Sydney (Figure1). The coastal eco-geomorphic system of the Wandandian Delta is located at the end of Wandandian Creek where the channel is actively prograding into St. Georges Basin (Figure1) that is separated from the South Pacific Ocean by a sandy barrier [14]. The shallow St. Georges Basin has rock outcrops that control where the Wandandian fluvial sediment can accumulate and build the deltaic system over time [15,16]. The Wandandian eco-geomorphic system has been considered as a sensitive area that includes (i) fluvial platforms, and (ii) intensive vegetation cover, such as mangroves and Casuarina [17,18]. Wandandian Creek is 25 km long starting from the eastern cliffs of the Tianjara Range (part of east Australian Great Dividing Range) to indirectly discharge to the southern Pacific Ocean via St. George Basin, a typical wave dominated estuarine platform [15,19]. The 1.6 m deep Wandandian Creek drains about 46% of St. Georges Basin catchment [20]. The deltaic system built by the Wandandian Creek sedimentary processes contains small areas of coastal wetlands (including mangrove, saltmarsh and back swamp) and intertidal flats on a fluvial bayhead delta [16]. J. Mar. Sci. Eng. 2017, 5, 55 3 of 21 J. Mar. Sci. Eng. 2017, 5, 55 3 of 21

Figure 1. The study site, of the coastal deltaic section of Wandandian Creek, southeast NSW, Figure 1. The study site, of the coastal deltaic section of Wandandian Creek, southeast NSW, Australia, Australia, illustrating; (a) location of New South Wales (NSW) in eastern Australia, (b) the study site illustrating;located on (a) the location mid-southern of New NSW South coast, Wales (c) (NSW)the regional in eastern setting Australia, showing the (b )St. the Georges study siteBasin located and on the mid-southernthe catchment NSWarea of coast, Wandandian (c) the regional Creek, and setting (d) showingillustrates thethe St.deltaic Georges border, Basin elevation and the and catchment the area ofsampling Wandandian locations Creek, (WD1 andto WD18). (d) illustrates the deltaic border, elevation and the sampling locations (WD1 to WD18). 2.2. Catchment and Land Use Classes

2.2. CatchmentWandandian and Land Creek Use Classeshas a small catchment draining about 202.3 km2 ranging from high to irregularly sloped terrain with elevations from 0 to 709 m along the ~25 km long Wandandian Creek. Wandandian Creek has a small catchment draining about 202.3 km2 ranging from high to This represents an average 3.5% slope along the main creek channel, but the slope is much higher in irregularly sloped terrain with elevations from 0 to 709 m along the ~25 km long Wandandian Creek. the upper parts of the valleys (Figure 2a, [14]). The Wandandian Creek catchment contains the ThisWandandian, represents an Bewong, average Tullarwalla 3.5% slope and along Jerrawangala the main villages creek that channel, are neighboured but the slopeby quite is intensive much higher in therural upper activities parts [15]. of theThis valleys region has (Figure a population2a, [ 14 of]). about The 15,000 Wandandian [14,21] but Creek this will catchment increase as contains urban the Wandandian,development Bewong, expands Tullarwalla [14]. St. andGeorges Jerrawangala Basin is a villagespopular that holiday are neighboured destination known by quite for intensive its ruralrecreational activities [activities15]. This such region as sightseeing, has a population bushwalking, of about fishing, 15,000 water [skiing14,21 ]and but sailing. this will increase as urban developmentHuman settlement expands in the [14 catchment]. St. Georges began Basin in 183 is0 and a popular by 1900 holidayhad established destination grazing, known urban for its recreationalareas and activities other modifications such as sightseeing, over 22% of bushwalking, the catchment ﬁshing, (see Figure water 2b). skiing These and transitions sailing. in land Humanuse were settlementassociated with in the clearing catchment native began vegetation, in 1830 resulting and by in 1900 changes had to established the drainage grazing, network urban hydrology and eco-geomorphologic characteristics of the catchment and its runoff and sedimentary areas and other modiﬁcations over 22% of the catchment (see Figure2b). These transitions in land processes [3,22]. Large areas of the catchment are still covered with native vegetation (74.2%) use were associated with clearing native vegetation, resulting in changes to the drainage network including a state forest and a national park along the eastern cliffs of the Tianjara Range (Figure 2). hydrology and eco-geomorphologic characteristics of the catchment and its runoff and sedimentary processes [3,22]. Large areas of the catchment are still covered with native vegetation (74.2%) including a state forest and a national park along the eastern cliffs of the Tianjara Range (Figure2). Early land clearing affected the eco-geomorphic systems in the lower catchment and its dependent downstream J. Mar. Sci. Eng. 2017, 5, 55 4 of 21 J. Mar. Sci. Eng. 2017, 5, 55 4 of 21 areasEarly but duringland clearing the study affected period the eco-geomorphic has only included systems minor in additionalthe lower catchment urban development and its dependent (Figure 2). Sanddownstream mining operations areas but for during construction the study materials period in has the lateonly1960s included through minor to theadditional early1970s urban in the lowerdevelopment deltaic reach (Figure of Wandandian 2). Sand mining Creek operations increased for construction water depths materials and affect in the sedimentation late 1960s through rates for to the early 1970s in the lower deltaic reach of Wandandian Creek increased water depths and affect over a decade. The dredging also opened the creek to recreational users and wake waves enhanced sedimentation rates for over a decade. The dredging also opened the creek to recreational users and bankwake erosion. waves enhanced bank erosion.

FigureFigure 2. Landcover 2. Landcover elevation elevation andand patterns patterns within within Wan Wandandiandandian Creek Creek catchment catchment area, showing; area, showing; (a) (a) thethe elevation elevationof ofthe the catchmentcatchment illustrating the the terrain terrain and and high high sloped sloped watershed watershed (using (using Australian Australian height vertical datum at 1.024 m MSL), the 1-metre digital elevation model (DEM) is derived from C3 height vertical datum at 1.024 m MSL), the 1-metre digital elevation model (DEM) is derived from C3 LiDAR (Light Detection and Ranging) obtained by LPI on 19 September 2016 [23]. (b) Land use classes LiDAR (Light Detection and Ranging) obtained by LPI on 19 September 2016 [23]. (b) Land use classes and areas (km2). Source after [15,17,18,23]. and areas (km2). Source after [15,17,18,23]. 2.3. Local Climate Conditions 2.3. Local Climate Conditions The main climate factors that could have major effects on the eco-geomorphic processes are Theprecipitation main climate (and the factors resultant that river could discharge have in major the Wandandian effects on watershed the eco-geomorphic area), temperature processes and are precipitationmean sea (andlevel theat/around resultant the riverdeltaic discharge system (Figures in the 3 Wandandian and 4). watershed area), temperature and mean seaWandandian level at/around catchment the deltaic has a systemtemperate (Figures oceanic3 climateand4). (Cfb) with no dry season [23], which promotes weathering and sediment production [24]. The average temperatures range from 11.5 °C in Wandandian catchment has a temperate oceanic climate (Cfb) with no dry season [23], winter (July and August) to 21 °C during summer (January and February; data from Sussex Inlet which promotes weathering and sediment production [24]. The average temperatures range from ◦Bowling Club gauging station; Figure 3; ◦[15]). Rainfall in the Wandandian Creek catchment is highest 11.5 inC latein winter summer (July and andautumn, August) whereas to 21 theC lowest during rainfall summer occurs (January in late winter and February; and spring data [25]. from Sussex Inlet BowlingAverage Club rainfall gauging in the station; Wandandian Figure catchment3;[ 15]). is Rainfall 1300 mm/year in the Wandandianleading to an estimated Creek catchment annual is highestrunoff in late of 400 summer mm [16,26]. and autumn,Five major whereas flood events the lowestbetween rainfall 1985 and occurs 2015 have in late been winter identified and within spring [25]. Averagethe Wandandian rainfall catchment in the Wandandian (Figure 4a,b). catchment They occurred is 1300 in March mm/year 1959, October leading 1959, to an February estimated 1971, annual runoffJune of 4001991 mm and [August16,26]. 2015. Five Nine major additional flood events minor between flood events 1985 occurred and 2015 in May have 1953, been February identified 1958, within the WandandianMarch 1961, catchmentMarch 1975, (Figure March 41976,a,b). TheyOctober occurred 1976, February in March 1992, 1959, September October 1993, 1959, April February 1994, 1971, June 1991March and 2011, August March 2015.2012 and Nine June additional 2013 (Figure minor 4a,b); flood [23,27,28]). events occurred in May 1953, February 1958, March 1961, March 1975, March 1976, October 1976, February 1992, September 1993, April 1994, March 2011, March 2012 and June 2013 (Figure4a,b); [23,27,28]). J. Mar. Sci. Eng. 2017, 5, 55 5 of 21

J. Mar.In Sci. terms Eng. 2017 of ,climate5, 55 change at the study site, temperature and sea level are slowly rising (Figure5 of 21 4c,d),J. whichMar. Sci. Eng.reflects 2017, 5the, 55 global warming trend [2,29]. Air temperature shows a clear overall5 ofincrease 21 duringIn the termsIn lastterms of five of climate climatedecades, changechange with at atnumerous the the study study site, fluc site, temperaturetuations. temperature The and increasing sea and level sea are temperature slowly level arerising slowly would (Figure risingaffect (Figuresedimentological4c,d),4c,d), which which reflects processes reflects the global and the globalplan warmingt productivity, warming trend [2, trend29]. which Air [ 2 temperature,29 logically]. Air temperature would shows ahave clear shows an overall effect a clearincrease on the overall eco- increasegeomorphicduring during the system. last the five last decades, five decades, with numerous with numerous fluctuations. fluctuations. The increasing The increasing temperature temperature would affect would affectsedimentological sedimentological processes processes and andplan plantt productivity, productivity, which which logically logically would have would an haveeffect anon effectthe eco- on the geomorphic system. eco-geomorphic system. Rainfall Temperature 160 25 Rainfall Temperature 140

160 25 C)

20 ° 120 140 C)

100 20 ° 120 15 80 100 15 10 60 80 40 60 10 5 40 20 5 mean monthly (mm) rainfall 0 20 0 mean monthly temperature ( mean monthly (mm) rainfall 0Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec mean monthly temperature (

Figure 3. Monthly data for temperature and precipitation for Wandandian area during this study Figure 3. Monthly data for temperature and precipitation for Wandandian area during this study Figureperiod 3.showMonthly that the data highest for temperature seasonal temperature and precipitation occurs forduring Wandandian the south area hemisphere during this summer, study period show that the highest seasonal temperature occurs during the south hemisphere summer, periodparticularly show in that January the highest and February. seasonal At temperature the same time, occurs February during and the March south are hemisphere the wettest summer, months particularlyparticularly in January in January and and February. February. At At the the same same time, time, February February and March are are the the wettest wettest months months in in thein records the records [15,24,30]. [15,24,30]. the records [15,24,30]. The reportedThereported reported local local local mean mean mean sea sea levelsea level level rise riserise (MSLR; (MSLR;(MSLR; Figure FigureFigure4d) is4d) 4d) caused is iscaused caused by globalby byglobal warmingglobal warming warming and and climate and changeclimateclimate [change2,29 change]. It[2,29]. is [2,29]. based It is It based onis based mean on on mean water mean water water level level relative relativerelative to the to to the nearestthe nearest nearest local local local tidetide tide gauging gauging gauging station station station at Portat Portat Kembla, PortKembla, Kembla, which which which is is located locatedis located ~45 ~45 ~45 kmkm km away away but has has an an an observation observation observation record record record extending extending extending from from 1957 from 1957to 1957 to torecent recentrecent [31]. [31 [31]. ].

Figure 4. Climate trends for Wandandian Creek estuary; (a) the total monthly precipitation, (b) annual flow discharge in Wandandian Creek, (c) mean annual air temperature, and (d) monthly mean sea level at Port Kembla (1957 to 2016; red is the maximum, green is the mean, and blue is the Figureminimum). 4. Climate Sources trends [24,30]for Wand Wandandian. andian Creek estuary; (a)) the total monthly precipitation, ((b)) annual flow discharge in Wandandian Creek, (cc) mean annual air temperature, and (d) monthly mean sea ﬂow discharge in Wandandian Creek, ( ) mean annual air temperature, and ( ) monthly mean sea levellevel atat PortPort Kembla Kembla (1957 (1957 to to 2016; 2016; red red is the is maximum,the maximum, green green is the is mean, the andmean, blue and is the blue minimum). is the Sourcesminimum). [24,30 Sources]. [24,30].

J. Mar. Sci. Eng. 2017, 5, 55 6 of 21

J. Mar. Sci. Eng. 2017, 5, 55 6 of 21 Analysis of monthly data from this gauging station is based on 60 years’ time-series of sea-level measurementsAnalysis from of monthly 1957 to 2016.data from Figure this4 dgauging clearly statio showsn is that based sea on level 60 years’ at Port time-series Kembla of has sea-level fluctuated and risen.measurements The monthly from average1957 to 2016. mean Figure sea level4d clearly at Port shows Kembla that sea is level 0.907 at m, Port and Kembla the maximum has fluctuated recorded was 2.233and risen. m on The 19 Augustmonthly 2001,average whereas, mean sea the level minimum at Port Kembla recorded is 0.907 was m, on and 4 December the maximum 1994 recorded at −0.217 m. The overallwas 2.233 average m on trend19 August of SLR 2001, at Portwhereas, Kembla the mi isnimum 0.035 m recorded from 0.895 was to on 0.930 4 December m during 1994 last at six−0.217 decades. Them. The channel overall linking average St. trend Georges of SLR Basin at Port to Kembla the open is 0.035 ocean m isfrom restricted 0.895 to and0.930 the m during basin haslast asix much reduceddecades. tidal range and an elevated water level of about 1.23 m AHD (data from Island Point Station The channel linking St. Georges Basin to the open ocean is restricted and the basin has a much 216415 in northern St. Georges Basin). This means water level fluctuations within St. Georges Basin reduced tidal range and an elevated water level of about 1.23 m AHD (data from Island Point Station have less influence than in other coastal examples since there is very little tidal influence coming into 216415 in northern St. Georges Basin). This means water level fluctuations within St. Georges Basin this largehave basinless influence with restricted than in other connection coastal examples to the Pacific since there Ocean. is very Thus, little water tidal influence flows from coming Wandandian into Creekthis will large always basin with be attenuated restricted connection as they enter to the thePacific basin Ocean. giving Thus, rise wate tor moreflows from sediment Wandandian deposition opportunitiesCreek will on always the delta be attenuated that can develop as they habitatenter the accommodation basin giving rise and to ecosystemmore sediment diversity. deposition Sea level rise isopportunities still likely to on influence the delta the that basin can anddevelop can habitat be used accommodation to assess the eco-geomorphic and ecosystem diversity. changes, Sea such as shorelinelevel dynamicsrise is still likely and coastal to influence wetland the basin responses. and can be used to assess the eco-geomorphic changes, such as shoreline dynamics and coastal wetland responses. 3. Materials and Methods 3. Materials and Methods GIS mapping, monitoring and modelling has been used to investigate the landcover classes GIS mapping, monitoring and modelling has been used to investigate the landcover classes dynamics, shoreline movement, sedimentation rates and the general deltaic progradation based on dynamics, shoreline movement, sedimentation rates and the general deltaic progradation based on local literature, aerial photography, and satellite imagery. The GIS analysis was supported by previous local literature, aerial photography, and satellite imagery. The GIS analysis was supported by investigationsprevious investigations of vegetation, of sediment vegetation, sampling, sediment particlesampling, size, particle X-ray size, diffraction X-ray diffraction (XRD), loss(XRD), on loss ignition (LOI)on and ignition water (LOI) quality and analyses water quality [16]. Thisanalyses study [16]. divided This study the methodology divided the methodology into three parts, into asthree seen in Figureparts,5. as seen in Figure 5.

FigureFigure 5. Methodology,5. Methodology, data data collectioncollection and and analysis analysis sequences. sequences.

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3.1. Data Collection Various data have been collected to achieve the study aims. RS and GIS datasets were used to analysis land covers. Light Detection and Ranging (LiDAR; 2004 and 2010) and SRTM (2011) data have been used in ArcGIS to create DEMs. These survey data for the Wandandian area were provided by the Department of Land and Property Information (LPI) in NSW. These data record the surface elevation as heights (Z values) relative to a local zero level datum. The data also incorporated the actual local mean sea level at the time of the survey based on the tidal/time dynamics from the local ground base-stations at the Sussex Inlet Bowling Club and the Island Point Station in St. Georges Basin. The DEM was generated using a TIN and the contour spatial analyst tools in ArcGIS. Meanwhile, aerial photography was obtained from the LPI and the landsat satellite imagery from the USGS (https://earthexplorer.usgs.gov/). Sediment and soil samples were collected as vibracores from the Wandandian Delta (Figure1) to represent all the recognized sedimentary facies [16]. Surface material was subsampled and analysed for grain size, mineralogy (using X-ray diffraction; XRD, Panalytical, Almelo, Holland) and organic matter (by loss on ignition; LOI, Ceramic Engineering, Sydney, Australia) to categorise each facies. The pH, conductivity, dissolved oxygen, salinity and turbidity were measured in the ﬁeld using a Yeo-Kal 615 multi-parameter water quality analyser. These data were combined with previous detailed stratigraphic data from the vibracores [16].

3.2. Data Analysis All images were rectified by using 20 training points within an average of 15 to 25 pixels as a finger print; this has been done for each class in every single satellite tail. We used the pixel to pixel validation method using an existing vector based classification of this study site provided by LPI in 2014. The vector layer was then converted to a raster and the ERDAS IMAGINE (Hexagon Geospatial, Madison, AL, USA) validation tool was run to test our results, which showed high accuracy. Assessment and measurement are based on the land cover derived from aerial photographs (1949, 1961, 1972, and 1993) and satellite images (2002 and 2016) over time using the standard self-adaptive/minimum distance-adjustment combined with the fuzzy membership function. The fuzzy classification method distinguishes the spatial features on the imagery according to fuzzy rules about the pixels membership functions to give more reliable and realistic outputs. Simultaneously, it will not allow pixels to be incomplete-members of multiple classes, which could lead to ambiguous/uncertain assignation of the resultant classes [31–33]. Analysis of the shoreline has determined the progradation of Wandandian deltaic system. Changes to the levees and shorelines and their associated wetlands, including mangrove and saltmarsh areas (as a land cover function), illustrate the shoreline position and elevation stability in the area. This project entails assessing potential threats, such as shoreline erosion and sediment delivery problems. In addition, the effects of artificial modification in the catchment are the principle element addressed. The project targets are achieved at several levels, starting with GIS and RS-based analysis to identify and classify the land cover and shoreline changes at specific study sites depending on recent and historical records of aerial photography, satellite and LiDAR data. This was combined with sampling the water, soil and sediment. Pre-processing of the employed imagery and aerial photographs was done to produce radiometrically and geometrically rectified framework parameters, including the local coordinate system and datum (GDA-MGA-1994/zone 56), atmospheric issues, and pixel size. To analyse datasets with various resolutions and to make the multi-temporal data comparable for valid use in research, this paper has scaled the pixel sizes to a uniform spacing and converted the imagery pixels to the same scale as the resolution of the aerial photographs to assure common pixel extents, which resulted in errors of ±0.0125 to ±0.0375 m. As part of the standard procedure, statistical weighting was used to cope with rescaling to a common pixel spacing and to accommodate images across multiple dates. J. Mar. Sci. Eng. 2017, 5, 55 8 of 21

During this rescaling some neighbourhood weighting is needed to make sure that the output values are radiometrically equivalent, rather than visually smooth. To analyse shoreline changes, the Digital Shoreline Analysis System (DSAS) was used on the dynamic shoreline positions of the delta (after dividing them into sections a–f; see Figure 10) derived from the employed datasets between 1949 and 2016. The DSAS also quantiﬁed the rate of deltaic progradation over a 66-year period (Figure 10). The DSAS analysis used many transects sampled along shorelines at 50 m intervals from an offshore baseline around the deltaic facies and levees (Figure 10a–f). To calculate the rates of shoreline changes over the study period, two statistical methods were used: the net shoreline movement (NSM)/envelope to track the changes, and the linear regression rate (LRR) to evaluate the results [34,35].

4. Results A spatiotemporal deltaic dynamic evaluation has been established, using a stratigraphic description derived from remote sensing datasets, GIS analyses and fieldwork sampling, to highlight the deltaic changes including shoreline erosion/accretion rates and landcover change (e.g., vegetation canopy). Eco-geomorphic changes to the Wandandian Delta were detected using ArcGIS, digital shoreline analyses system (DSAS) and geomorphic change detection (GCD) based on aerial photography and satellite imagery. These changes were related to most effective controlling factors through sedimentology analyses and catchment assessment. Thus, a three level simulation approach for evaluation of the Wandandian deltaic system was based on geochronological data at the landscape scale. The coastal eco-geomorphic changes, caused by deltaic progradation and land use development have resulted in expansion of the Wandandian deltaic eco-geomorphic systems, including growth and establishment of saltmarsh, mangrove and mudﬂat shorelines (Figures6 and7).

4.1. Multitemporal Imagery Classiﬁcation The multitemporal analysis of remote sensing (RS) and GIS data (Figure6) indicates that the river channel has actively prograded moving sediment brought down from the catchment to the mouth of the delta. This has built an interesting deltaic system at the Wandandian Creek mouth, which has grown geomorphologically since at least 1949 to offer suitable ecosystem habitats for wetland colonisation. In addition, there is clear evidence of landcover development on the main deltaic platform since the 1940s (Figure6). The Wandandian Delta is under constant eco-geomorphic growth due to both natural (e.g., weathering/erosion, deposition) and indirect anthropogenic forces (including human activities, climate change and sea level rise). During the Holocene, the Wandandian Delta started to inﬁll and prograde into the western part of St. Georges Basin [15,16] with more accommodation space being generated during the current sea level rise (Figure6 shown in red and pink). Geomorphic development has led to ecosystem expansion onto sensitive deltaic areas as shown by the landuse classes (Figure6). Growth of the Wandandian deltaic eco-geomorphic system of vegetation canopy and deltaic facies is due to the protected ecosystem allowing sediment accumulation. This has resulted in the active channel levees prograding into St. Georges Basin (Figure7) with elevations up to 1.5 m above water level [15]. Vegetation canopy growth has played an important role in stabilising and expediting the shoreline/levee expansion and vertical accretion (Figure7). J. Mar. Sci. Eng. 2017, 5, 55 9 of 21 J. Mar. Sci. Eng. 2017, 5, 55 9 of 21

Figure 6. Multi-temporal high resolution aerial photograph classifications for 1949, 1961, 1972, 1993, Figure 6. Multi-temporal high resolution aerial photograph classiﬁcations for 1949, 1961, 1972, 1993, 2002 and 2016 show progressive changes of Wandandian deltaic landform classes and shorelines. The 2002 and 2016 show progressive changes of Wandandian deltaic landform classes and shorelines. clearest changes have occurred on the levee and backswamp facies where increasing native and mixed The clearest changes have occurred on the levee and backswamp facies where increasing native and vegetation canopy indicates progressive eco-geomorphic stability. Prograded sand and silt bars have mixed vegetation canopy indicates progressive eco-geomorphic stability. Prograded sand and silt bars grownhave grown since since1949 1949and andadded added more more geomorphic geomorphic acco accommodationmmodation habitat, habitat, thus thus allowing allowing ecological ecological development to continue.

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Figure 7. Vegetation canopy acting positively to assist the geomorphic growth and to develop the Figure 7. Vegetation canopy acting positively to assist the geomorphic growth and to develop the deltaic ecosystem; (a) Casuarina has vegetated the outer edge of the subaerial portion of the mouth deltaic ecosystem; (a) Casuarina has vegetated the outer edge of the subaerial portion of the mouth bar bar whereas the depressed swampy portion in the centre of the bar is dominated by Juncus. (b) whereasCasuarina the depressed and Juncus swampy stabilising portion and expediting in the centre vertical of the accretion bar is dominatedof the subaerial by Juncus portions.(b )ofCasuarina the and JuncusWandandianstabilising Creek anddelta expediting (levees and verticalmouth bars; accretion after [15]). of the subaerial portions of the Wandandian Creek delta (levees and mouth bars; after [15]). Charcoal in the basal fraction of the palaeoswamp facies suggests that at the time of deposition Charcoalrelatively frequent in the basal fire events fraction occurred of the palaeoswampin the area [15,16]. facies Growth suggests of levees that and at the delta time front of depositionfacies have become suitable habitats for new ecosystems, including; mangrove and saltmarsh, as well as the relatively frequent ﬁre events occurred in the area [15,16]. Growth of levees and delta front facies native plants such as Casuarina, eucalypts and Juncus, which have continued to stabilise the estuarine have become suitable habitats for new ecosystems, including; mangrove and saltmarsh, as well as the deltaic ecosystem (Figure 7a,b). The biotic detritus has accumulated as organic matter within the nativesedimentary plants such sequences. as Casuarina , eucalypts and Juncus, which have continued to stabilise the estuarine deltaic ecosystemThe high-resolution (Figure7a,b). aerial The photography biotic detritus analysis has (Figure accumulated 6) shows asWandandian organic matter deltaic within facies the sedimentaryprogradation sequences. and growth into St. Georges Basin in red and graded red. Clear spatial patterns of Theaccelerated high-resolution accumulation aerial of sedi photographyment in the analysisWandandian (Figure system6) shows are shown Wandandian in Figures deltaic 6 and 7. facies progradationMeasurements and growthof deltaic intoprogradation St. Georges including Basin rate ins, redtotaland and net graded growth red. are summarised Clear spatial in Table patterns 1 of acceleratedand Figure accumulation 8. of sediment in the Wandandian system are shown in Figures6 and7. Measurements of deltaic progradation including rates, total and net growth are summarised in Table1 4.2. Wandandian Deltaic Growth (1949–2016) and Figure8. Figures 6 and 8 have derived growth evidence from the Wandandian deltaic eco-geomorphic 4.2. Wandandiansystem, particularly Deltaic Growthon the delta (1949–2016) front facies and the adjacent shorelines. The area of the delta has been calculated for: (i) the subaerial, (ii) subaqueous delta borders and (iii) the total area (Table 1) Figuresthus providing6 and8 annual have derivedrates of sedimentation growth evidence during from the study the Wandandian period (1949–2016), deltaic as eco-geomorphic illustrated in system,Figure particularly 9. on the delta front facies and the adjacent shorelines. The area of the delta has been calculated for: (i) the subaerial, (ii) subaqueous delta borders and (iii) the total area (Table1) thus providing annual rates of sedimentation during the study period (1949–2016), as illustrated in Figure9. Table1 shows that the delta grew by 14% (242,860 m 2) over the study period (1949–2016) at an average rate of 4168 m2/year, with highest rates being 5283 and 8554 m2 for 1949–1961 and 1961–1972, J. Mar. Sci. Eng. 2017, 5, 55 11 of 21 J. Mar. Sci. Eng. 2017, 5, 55 11 of 21 respectively.Table The 1 shows reduced that delta the delta growth grew between by 14% (242,860 1972 and m 19932) over probably the study reﬂects period sediment(1949–2016) trapping at an in the sandaverage mining rate of area 4168 on m2 Wandandian/year, with highest Creek. rates The being subaerial 5283 and area 8554 hasm2 for grown 1949–1961 by 29,130 and 1961–1972, m2, allowing suitablerespectively. ecological The accommodation reduced delta growth to be between inhabited. 1972 and The 1993 intertidal probably and reflects subaqueous sediment areatrapping grew by 213,730in the m2 sandinto mining a protected area on part Wandandian of St Georges Creek Basin. The subaerial preparing area a has great grown opportunity by 29,130 form2, theallowing subaerial area tosuitable expand ecological more positively accommodation in the futureto be inhabite (Figured.8). The intertidal and subaqueous area grew by 213,730 m2 into a protected part of St Georges Basin preparing a great opportunity for the subaerial area to expand more positively in the future (Figure 8). Table 1. Area analyses of the Wandandian Delta for the overall delta growth, subaqueous area, total sensitive area, and average deltaic progradation *. Table 1. Area analyses of the Wandandian Delta for the overall delta growth, subaqueous area, total sensitive area, and average deltaic progradation *. Subaerial Area Subaqueous Total Sensitive Total Growth Growth/Year Aerial Photograph Subaerial2 Subaqueous 2 Total Sensitive 2 Total Growth2 Growth/Year2 Aerial Photograph (km ) Area (km ) Area (km ) (m ) (m /year) Area (km2) Area (km2) Area (km2) (m2) (m2/year) 1949 1.7112 0.1679 1.8791 - - 1949 1.7112 0.1679 1.8791 - - 19611961 1.71251.7125 0.23 0.23 1.9425 1.9425 63,400 63,400 5283 5283 19721972 1.71341.7134 0.3232 0.3232 2.0366 2.0366 94,100 94,100 8554 8554 19931993 1.72981.7298 0.3319 0.3319 2.0617 2.0617 25,100 25,100 1195 1195 20022002 1.73561.7356 0.364 0.364 2.0996 2.0996 37,900 37,900 4211 4211 20162016 1.740331.74033 0.38163 0.38163 2.12196 2.12196 22,360 22,360 1597 1597 2 ChangesChanges (m ) (m2) 29,13029,130 213,730 213,730 242,860 242,860 242,860 242,860 4168 4168 ** Sources: Sources: Figure Figure 66 andand thethe calculatecalculate geometrygeometry tool tool of of the the data data management management package package in in ArcGIS, ArcGIS, (after (after [15 [15,33]).,33]).

Subaerial area Total sensitive area 2.3 2.2 2.1 2 1.9

Area (sq. Km) Area (sq. 1.8 1.7 1.6 1.5 1949 1952 1955 1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 Time (year)

FigureFigure 8. Wandandian 8. Wandandian deltaic deltaic growth, growth, illustratingillustrating the the overall overall growth growth of ofthe thedelta delta itself itself and andits its levees/shorelines (blue), as well as the total growth of sensitive subaqueous areas (red). levees/shorelines (blue), as well as the total growth of sensitive subaqueous areas (red). 4.3. Tracing the Shoreline Temporal Movement 4.3. Tracing the Shoreline Temporal Movement Evidence of shoreline movements in Figures 6–8, and the more detailed example in Figure 9, is Evidencea call for more of shoreline shoreline movements dynamic analysis. in Figures The 6frictional–8, and theinteraction more detailed between example the outflowing in Figure river9, is a call forwater more and shoreline the sediment dynamic surface analysis. [36] in The the frictional shallow western interaction distributary between channel the outflowing resulted riverin the water and thedeposition sediment of surfacea triangular [36] inmidchannel the shallow bar western that caused distributary the channel channel to bifurcate resulted forming in the depositiona typical of a triangularfluvial-dominated midchannel birdsfoot bar that delta caused morphology the channel [37–39]. to The bifurcate subaqueous forming portion a typical of the fluvial-dominateddelta coarsens birdsfootupwards delta whereas morphology the subaerial [37–39 ].portion The subaqueous of the interdistributary portion of thebar deltafines upwards coarsens from upwards relatively whereas clean mouthbar sand to muddy finer sand interbedded with dark carbonaceous silt lenses [15,16]. the subaerial portion of the interdistributary bar fines upwards from relatively clean mouthbar sand to Most of the fluvial sediments passed into delta mouth via the active tidal channel are eroded muddyand finer redeposited sand interbedded on the margins with of darkSt. Georges carbonaceous Basin (Figure silt lenses9). A more [15, 16detailed]. dynamic analysis of Mostthe deltaic of the shoreline fluvial sedimentsis shown in passedFigure 10. into delta mouth via the active tidal channel are eroded and redeposited on the margins of St. Georges Basin (Figure9). A more detailed dynamic analysis of the deltaic shoreline is shown in Figure 10.

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Figure 9. Subaqueous and subaerially exposed levees associated with the western distributary Figure 9. Subaqueous and subaerially exposed levees associated with the western distributary channel channel of the Wandandian Creek delta. Source: LPI, 50 cm Jervis Bay and Ulladulla surveys of of the Wandandian Creek delta. Source: LPI, 50 cm Jervis Bay and Ulladulla surveys of January 2014. January 2014.

Shoreline movements of Wandandian Creek delta havehave been captured using the digital shoreline analysis system (DSAS). Figure 10 shows clear growth (green) in the active delta areas. On the other hand, somesome erosionerosion occurredoccurred along along the the landward landward side side of theof the upper upper active active channel channel (Figure (Figure 10a,b,f) 10a,b,f) part partof its of southern its southern bank, bank, as well as well as small as small portion portion of the of delta-front the delta-front island island (Figure (Figure 10e). 10e). The overall average shoreline extension was 1.451 m/yearm/year (Figure (Figure 10)10) but but some zones show shoreline erosion rates of up to 0.348 m/year. Thes Thesee changes changes occurred occurred along some parts of the deltaic landform facies facies and and are are more more concentrated concentrated on on the the southern southern part part of of the the delta delta at at the the creek creek mouth. mouth. Accretion was concentrated on the left side of th thee delta (on and around the large island, Figure 10d10d and levees of sections b and c), with a net shoreline movement of 2.87 m over the past 65 years. Most of the sediment movementmovement occursoccurs duringduringﬂood flood conditions conditions but but movement movement around around the the delta delta margins margins is isalso also affected affected by by minor minor tidal tidal ﬂows flows and and wind-wave wind-wave action. action.

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Figure 10. Digital shoreline analysis system (DSAS) applied to the sensitive Wandandian Delta shows Figureshoreline 10. Digital erosion shoreline in red, accretion analysis in system green (DSAS)while yellow applied represents to the the sensitive stable zones. Wandandian Attached Delta charts shows shorelineshow erosionthe net shoreline in red, accretion movement in envelope green while between yellow 1949 and represents 2016: (a)the the stableupper channel; zones. Attached(b) western charts showportion the net of shoreline the delta; movement (c) the mid envelope delta; (d) betweenlarge interdistributary 1949 and 2016: island; (a) the (e) uppersmall mouthbar channel; (island;b) western portionand of(f)the eastern delta; portion (c) the of the mid delta. delta; (d) large interdistributary island; (e) small mouthbar island; and (f) eastern portion of the delta. 4.4. Fieldwork and Sampling 4.4. Fieldwork and Sampling 4.4.1. Soil and Sediment Samples 4.4.1. SoilThe and soil Sediment and sediment Samples sample locations (Figures 1 and 12) and analyses have linked the detected shoreline changes to a better understanding of the Holocene facies distribution and sedimentation The soil and sediment sample locations (Figures1 and12) and analyses have linked the detected patterns. A detailed description of the stratigraphy of the Wandandian Delta and its substrate has shorelinebeen changespresented toin a[15,16]. better Initial understanding deposition ofof thefluvial Holocene sands and facies overbank distribution deposits and progressively sedimentation patterns.filled Athe detailed Pleistocene description low stand ofpalaeochannel the stratigraphy before ofreaching the Wandandian St Georges Basi Deltan. Progradation and its substrate of the has beenWandandian presented in Delta [15, 16into]. the Initial broader deposition embayment of ﬂuvial on the sandswestern and margin overbank of St. Georges deposits Basin progressively began ﬁlledapproximately the Pleistocene 3.5–4 low kastand [16] with palaeochannel the prodelta/lagoon beforeal reaching mud facies St being Georges overlain Basin. successively Progradation by the of the Wandandiandelta-front Delta sandy into silt facies the broader and the embaymentprograded sand on fa thecies western (Figure 11b). margin However, of St. in Georges the inner Basin part of began approximatelythis embayment 3.5–4 the ka latter [16] withtwo facies the prodelta/lagoonal are mainly separated mud by 1–2 facies m thick being organic-rich overlain successivelyaccumulations by the delta-frontrepresenting sandy asilt palaeoswamp facies and environment the prograded (Figure sand 11 faciesa). The (Figure prograded 11b). sand However, facies includes in the inner mouth part of this embayment the latter two facies are mainly separated by 1–2 m thick organic-rich accumulations representing a palaeoswamp environment (Figure 11a). The prograded sand facies includes mouth bar, subaqueous channel and levee, and wave-reworked delta-front deposits. In the innermost protected J. Mar. Sci. Eng. 2017, 5, 55 14 of 21 J. Mar. Sci. Eng. 2017, 5, 55 14 of 21

bar, subaqueous channel and levee, and wave-reworked delta-front deposits. In the innermost part of the embayment the prodelta sand facies is overlain by a younger prodelta/lagoonal mud facies protected part of the embayment the prodelta sand facies is overlain by a younger prodelta/lagoonal recordedmud facies in WD7 recorded (Figure in 11WD7a). (Figure 11a).

FigureFigure 11. 11.Cross-sections Cross-sections showing showing the distribution the distribution of prograded of prograded sand and organic-rich sand and silty organic-rich sequences silty sequencesin the inWandandian the Wandandian deltaic deltaicfacies, facies,which provide which provide suitable suitablebases for bases eco-geomorphic for eco-geomorphic growth. ( growth.a) Progradation of the western distributary into the embayment in St Georges Basin along vibracores: (a) Progradation of the western distributary into the embayment in St Georges Basin along vibracores: WD8 (west), WD7, WD9, WD6 and WD16 (east). (b) Eastern distributary through drill-holes WD15 WD8 (west), WD7, WD9, WD6 and WD16 (east). (b) Eastern distributary through drill-holes WD15 (southwest), WD14 and WD13 (northeast). Its eastern extent is controlled by an outcropping to (southwest),shallow subsurface WD14 and basement WD13 (northeast). high (after [15,16]). Its eastern extent is controlled by an outcropping to shallow subsurface basement high (after [15,16]). The rate of progradation of sandy facies in the Wandandian Creek delta is difficult to establish inThe the rate dynamic of progradation fluvial and delta of sandy mouth facies areas. in Very the few Wandandian macrofossils Creek live within delta these is difficult facies and to establish most in the dynamicof the recorded fluvial shells and deltaare reworked mouth or areas. broken Very maki fewng macrofossils them unsuitable live for within accurate these dating facies since and they most of the recordedare not in shells situ [15,40]. are reworked or broken making them unsuitable for accurate dating since they are not in situThe [15 mineralogy,40]. and grain size of the deltaic facies shows a clear relationship to the depositional energyThe mineralogy reflected in and the grainrelative size proportions of the deltaic of quartz facies in shows the sand a clear facies relationship and clay in tothe the fine depositional facies energy(Table reflected 2). Clay in content the relative in the samples proportions is highest of in quartz the low in energy the sand environments facies and in claysheltered in the reaches, fine facies but also occurs in the fluvial lithic sands through the diagenetic alteration of feldspar and rock (Table2). Clay content in the samples is highest in the low energy environments in sheltered reaches, fragments (Figure 12). Pyrite indicates reducing conditions in the organic-rich palaeoswamp and but also occurs in the fluvial lithic sands through the diagenetic alteration of feldspar and rock prodelta/lagoonal mud facies. fragments (Figure 12). Pyrite indicates reducing conditions in the organic-rich palaeoswamp and prodelta/lagoonalTable 2. X-ray mud diffraction facies. analyses of sediment samples from the Wandandian Delta showing mineral proportions (after [15]). Table 2. X-ray diffraction analyses of sedimentIllite- samplesMixed from Layer the Wandandian Delta showing mineral Facies Quartz % Albite % Kaolinite % Calcite % Pyrite % proportions (after [15]). Muscovite % Illite-Smectite % 85.7 4.3 8.8 0.3 0.8 0.1 0 Prograded Sand 86.6 2.5 0.5 7.9Mixed Layer 2.4 0 0.1 Facies Quartz % Albite % Illite-Muscovite % Kaolinite % Calcite % Pyrite % 92.1 0.2 3.2 Illite-Smectite4.2 % 0.3 0 0 51.1 0.2 27.0 14.4 1.6 0 5.7 Palaeoswamp 85.7 4.3 8.8 0.3 0.8 0.1 0 Prograded Sand 86.659.1 2.51.4 26.5 0.5 4.2 7.9 2.7 2.4 0 0 6.1 0.1 86.1 0.7 9.7 2.8 0.6 0 0.1 Delta sandy Silt 92.1 0.2 3.2 4.2 0.3 0 0 78.5 0.4 7.3 10.8 2.9 0 0.1 51.1 0.2 27.0 14.4 1.6 0 5.7 Palaeoswamp 51.5 0.1 31.6 6.2 3.9 0.2 6.5 Prodelta/ 59.1 1.4 26.5 4.2 2.7 0 6.1 56.3 0.1 28.8 3.8 5.2 0.1 5.7 Lagoonal Mud 86.1 0.7 9.7 2.8 0.6 0 0.1 Delta sandy Silt 58.3 1.3 23.3 7.8 3.1 0 6.2 Channel Fill 78.587.2 0.40 0.6 7.3 9.3 10.82.9 2.90 00 0.1 Fluvial Sand 51.584.7 0.12.4 6.4 31.6 3.6 6.22.9 3.90 0.20 6.5 Prodelta/Lagoonal 56.3 0.1 28.8 3.8 5.2 0.1 5.7 Mud 58.3 1.3 23.3 7.8 3.1 0 6.2

Channel Fill 87.2 0 0.6 9.3 2.9 0 0 Fluvial Sand 84.7 2.4 6.4 3.6 2.9 0 0 J. Mar. Sci. Eng. 2017, 5, 55 15 of 21 J. Mar. Sci. Eng. 2017, 5, 55 15 of 21

(b) Overall mineral proportions

Mixed Calcite layer kaolinite 0.03% Pyrite illite- 2.45% 2.03% smectite 5.89% Illite 8.38%

Muscovite 5.57%

Albite 0.91% Quartz 74.73%

FigureFigure 12. 12.Soil Soil andand sedimentsediment samplessamples fromfromthe the WandandianWandandian deltaic deltaic landform, landform, illustrating: illustrating: ( a(a)) mineral mineral contentscontents inin eacheach sedimentsediment samplesample andand representedrepresented facies,facies, withwith aaclear cleardominance dominance ofof quartz,quartz, (b(b)) the the overalloverall mineralmineral proportionsproportions inin thethe sedimentsediment samples.samples. (The(The backgroundbackground isis fromfrom aa JervisJervis BayBay 5050 cmcm OrthorectiﬁedOrthorectified Image Image obtained obtained from from LPI LPI for for January January 2014 2014 [ 30[30]).]).

OrganicOrganic matter matter plays plays an an importantimportant rolerole in in the the ecosystem ecosystem developmentdevelopment andand growthgrowth onon intertidalintertidal sedimentarysedimentary deltaic deltaic landforms. landforms. The The amount amount of of organic organic matter matter in thein the sediment sediment is controlled is controlled by the by rate the ofrate organic of organic decomposition decomposition in the in sediment the sediment [14]. In [14] general,. In general, high rates high of rates total carbonof total dioxide carbon (TCOdioxide2), + + 4− 4− ammonium(TCO2), ammonium (NH4 ), and(NH silicate4 ), and (SiOsilicate4 )(SiO production,4 ) production, and oxygen and oxygen (O2) consumption (O2) consumption indicate indicate high respirationhigh respiration rates andrates correspond and correspond to high to organic high organi contentsc contents in the sediment in the sediment [14]. As [14]. the organicAs the organic matter degradesmatter degrades nutrients nutrients are released are released into the into water the columnwater column and become and become available available for plant for plant growth growth and ecosystemand ecosystem development. development. Organic Organic matter matter components components (%OM) (%OM) are are concentrated concentrated (Figure (Figure 13 13)) in in the the downstreamdownstream part part of of the the delta, delta, where where the the wetlands wetlands are are distributed. distributed. + + 4−4− 4−4− WhileWhile the the Wandandian Wandandian Delta Delta had had low low TCO TCO2,O2,2 O, NH2, NH4 ,4 and, and SiO SiO4 4 fluxes, fluxes, the the SiO SiO4 4 andand TCO TCO2 2 ++ fluxesfluxes exceededexceeded thethe NHNH44 fluxflux indicatingindicating thatthat denitrification,denitrification, carbonatecarbonate dissolutiondissolution oror decoupleddecoupled decompositiondecomposition ofof organicorganic matter were more importan importantt than than respiration respiration [14]. [14]. Aerobic Aerobic respiration respiration in incoastal coastal and and estuarine estuarine sediments sediments generally generally shows shows a flux a flux ratio ratio of 1TCO of 1TCO2:1.3O2:1.3O2 but2 thebut TCO the2 TCO flux2 influx the inWandandian the Wandandian Delta Deltaexceeded exceeded this ratio this indicating ratio indicating the importance the importance of anaerobic of anaerobic degradation degradation in these indeposits. these deposits. This was This confirmed was confirmed by the large by amount the large of amount gas, including of gas, H including2S, released H2 S,during released vibracoring during vibracoring[15,16]. [15,16].

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+ 4− Figure 13. Average (n = 3) organic matter (benthic nutrient), TCO2, O2, NH+ 4 , and SiO4− 4 in Figure 13. Average (n = 3) organic matter (benthic nutrient), TCO2,O2, NH4 , and SiO4 in Wandandian delta. Note that NH4+, +SiO44−,4 −and TCO2 were fluxing out of the sediment, whereas O2 Wandandian delta. Note that NH4 , SiO4 , and TCO2 were ﬂuxing out of the sediment, whereas O2 was fluxingwas ﬂuxing into intothe thesediment. sediment. TCO TCO2 was2 was determined determined by by alkalinity alkalinityand and conductivity conductivity titrations titrations for thisfor this studystudy site (after site (after [14]). [14 ]).

4.4.2. 4.4.2.Water Water Quality Quality WaterWater quality quality was was assessed assessed under under average average flow flow co conditionsnditions toto indicate indicate downstream downstream changes changes in in the mainthe main water water quality quality parameters. parameters. Figure Figure 14 14 show showss increases increases inin conductivity,conductivity, dissolved dissolved oxygen oxygen and and salinitysalinity towards towards the themouth mouth of the of the delta delta while while the the temperature temperature andand pHpH show show a verya very slight slight increase, increase, due to shallower water that was easier to heat (Table3). In contrast, turbidity has shown a decline in due to shallower water that was easier to heat (Table 3). In contrast, turbidity has shown a decline in the downstream direction because suspended sediment has flocculated and accumulated along the the downstream direction because suspended sediment has flocculated and accumulated along the delta channels as salinity increases. At the same time, the active channel flows more slowly towards delta thechannels coastal as end salinity of the delta increases. especially At the during same rising time, basin the water active levels channel (due toflows floods, more tides slowly or seiches), towards the coastalwhich end makes of the riverdelta lessespecially able to transportduring rising both bedloadbasin water and levels suspended (due sediments.to floods, tides These or results seiches), whichclearly makes indicate the river that less abundant able to sediment transport is transported both bedload to the and delta suspended leading to highsediments. rates of depositionThese results clearlyand indicate bank accretion that abundant in these sediment downstream is transporte areas. Thus,d to thethe sedimentdelta leading is basically to high spread rates acrossof deposition the and bankentire accretion estuary and in these the suspended downstream sediment areas. becomesThus, the less sediment and finer is duringbasically its spread movement across along the the entire estuaryWandandian and the Deltasuspended due to flocculation.sediment becomes less and finer during its movement along the

WandandianTable Delta 3. Proﬁle due depth to flocculation. and analysis of water temperature, salinity, dissolved oxygen (DO), conductivity and turbidity. Table 3. Profile depth and analysis of water temperature, salinity, dissolved oxygen (DO), conductivitySample and turbidity.Depth Temperature Salinity Conductivity Turbidity DO (%) No. (m) (◦C) (±0.05 ‰) (±0.05 mS/cm) (NTUs) Sample Depth Temperature Salinity DO Conductivity Turbidity WD8 −0.6 19.8 28.8 89.4 14.5 20.54 No. WD9(m) −1.1(°C) 21.2 (±0.05 29.1 ‰) 82.6(%) (±0.05 16.8 mS/cm) 19.1 (NTUs) WD8 WD17−0.6 −1.519.8 21.1 30.3 28.8 80.989.4 17.1214.5 19.1 20.54 WD16 −2.4 21.3 29.6 79.8 18.9 19.1 WD9 WD11−1.1 −1.9621.2 21.4 30.7 29.1 79.5582.6 20.416.8 21.9 19.1 WD17 Average−1.5 1.521.1 21.0 29.7 30.3 82.580.9 17.517.12 19.9 19.1 WD16 −2.4 21.3 29.6 79.8 18.9 19.1 WD11 −1.96 21.4 30.7 79.55 20.4 21.9 Average 1.5 21.0 29.7 82.5 17.5 19.9

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FigureFigure 14.14.Water Water sample sample analyses analyses show show spatial spatial changes changes in; in; conductivity, conductivity, salinity, salinity, dissolved dissolved oxygen oxygen and turbidity,and turbidity, (sample (sample locations locations have have presented presented on Figure on Figure1). 1).

5. Morphological Evolution of the Wandandian Delta 5. Morphological Evolution of the Wandandian Delta The knowledge gained by assessing accumulation rates through remote sensing datasets and The knowledge gained by assessing accumulation rates through remote sensing datasets and the GIS analytic system creates a better framework for assessing deltaic systems here and worldwide. the GIS analytic system creates a better framework for assessing deltaic systems here and worldwide. The multi-temporal changes analysis approach was able to quantify the eco-geomorphic changes on The multi-temporal changes analysis approach was able to quantify the eco-geomorphic changes on the Wandandian Delta case study, and shows a qualitative picture of changes in the pattern of land the Wandandian Delta case study, and shows a qualitative picture of changes in the pattern of land cover, banks and broad changes in the delta area since the start of suitable historical photographic cover, banks and broad changes in the delta area since the start of suitable historical photographic data in 1949 (Figures 7–9 and Table 1). The main features shown by the multitemporal deltaic changes data in 1949 (Figures7–9 and Table1). The main features shown by the multitemporal deltaic changes between 1949, 1961 and 1972 are in the delta front facies, which involved growth of the levees, deltaic between 1949, 1961 and 1972 are in the delta front facies, which involved growth of the levees, deltaic shoreline facies, a reduction in the width of the active channel, and changes to the areas of mangrove, shoreline facies, a reduction in the width of the active channel, and changes to the areas of mangrove, saltmarsh and some native plant canopy (Figures 6–8). The subaqueous zone and the active delta saltmarsh and some native plant canopy (Figures6–8). The subaqueous zone and the active delta channel, as well as some of the internal shorelines, experienced net accretion in all five analysed time channel, as well as some of the internal shorelines, experienced net accretion in all ﬁve analysed time intervals between 1949 and 2016 but especially from the 1940s to 1970s. Consequently, most of the intervals between 1949 and 2016 but especially from the 1940s to 1970s. Consequently, most of the extended areas have increased land covers by expansion of mangroves and saltmarshes. extended areas have increased land covers by expansion of mangroves and saltmarshes. The active channel of Wandandian Creek has bifurcated with the eastern distributary The active channel of Wandandian Creek has bifurcated with the eastern distributary prograding prograding onto the shallow rocky bed on the western side of the St. Georges Basin producing an onto the shallow rocky bed on the western side of the St. Georges Basin producing an elongate delta. elongate delta. In contrast, the western distributary extends into the middle of the bay forming a small birdsfoot delta. These delta extensions have resulted in expanded geomorphic units including levees, floodplain, sandspits and their associated land covers (Figures 6 and 10; [15]). Both

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In contrast, the western distributary extends into the middle of the bay forming a small birdsfoot delta. These delta extensions have resulted in expanded geomorphic units including levees, floodplain, sandspits and their associated land covers (Figures6 and 10;[ 15]). Both distributaries are characterised by well-defined subaqueous and subaerial levees up to 1.5 m above water level. These levees consist of coarse fluvial sand that fine upwards to silty sands with interbedded dark organic-rich silt lenses. The subaerial levees are rapidly stabilized mainly by Casuarina and Juncus (Figure7b). Additionally, most of the native plants and the new saltmarsh areas (seen in 1949) were growing on the stable sensitive areas and started mixing with mangroves in the tidal zones as an effect of sea level and the consequent water table rise (Figures4d and6). The mangrove cover has gained ground as a result of the shoreline expansion (Figures6 and8). The minimal wind-wave reworking in the western embayment of St. Georges Basin means that it represents an ideal environment for silt and organic matter accumulation as Wandandian Creek discharges load through the delta. A reduced sediment carrying capacity through the delta may reflect a lower river discharge (lower rainfall) or more probably represents gradual filling and abandonment of previously active channels [37]. The large woody detritus and abundant organic material present in the palaeoswamp and prodelta/lagoonal mud facies were mainly transported as rafted plant debris into these quiet water environments. Two distinct sand sheets in the upper part of the palaeoswamp facies (Figure 11a) probably represent large flood events. The palaeoswamp deposits typically have a distinctive hydrogen sulphide smell caused by anaerobic decomposition of organic matter in the presence of sulphate ions. Suspended sediment fluxes from the catchment and the progradation of geomorphic units are the major influences controlling this delta growth in an inner estuary, like St. Georges Basin [15,16]. The results of this study reveal some important aspects of human and natural effects influencing the sedimentary facies, shoreline growth and water quality of Wandandian Creek and its deltaic zone (Figures6–10). Water quality analysis (Table3 and Figure 14) has shown that sedimentation increases towards the delta head providing continued accumulation processes. The salinity shows a gradual increase downstream towards the marine influenced St. Georges Basin. The water temperature also increases due to the stagnated water and limited ocean water exchange in the inner parts of St. Georges Basin [14,15]. Meanwhile, the conductivity and turbidity have fluctuated but show a slight increase towards the delta mouth reflecting the influence of salinity and suspended sediment transport and accumulation along the creek. In contrast, dissolved oxygen shows a declining trend seaward, indicating that O2 consumption in the water column exceeded any replenishment from photosynthesis or the atmosphere. The deltaic progradation evidence comes from the geomorphic growth of 242,860 m2 over the study period (4168 m2 annually, Table1). Growth has resulted from the sediment delivered to the coastal zone through the Wandandian Creek drainage system from intermediate moderately modified catchment. This growth has provided good ecosystem accommodation for plant colonisation, with common organic matter accumulating within the sediment along the shorelines and in the interdistributary bays. This study has illustrated how careful analysis of remote sensing data using a GIS platform can lead to a detailed understanding of the growth and evolution of deltaic and estuarine systems and is similar to the results presented for other Australian coastal systems [3,4,19,41–43]. This implies that the methodology can be broadly applied to study morphological changes over relatively short timeframes in other coastal lagoon systems both in eastern Australia and more generally to any similar systems around the world.

6. Conclusions This investigation has effectively used remote sensing and GIS analysis to quantify historical and existing eco-geomorphic situations in deltas and use these to predict their future responses to related environmental stressors. Proven deltaic progradation has shown how estuaries can keep up J. Mar. Sci. Eng. 2017, 5, 55 19 of 21 with sea level rise through continuous sand/silt sediment accumulation derived from a partially modified catchment. The morphology of the Wandandian Creek delta has been influenced by both the shape of the shallow bedrock and Pleistocene outcrops and by recent anthropogenic modifications within the catchment. Delta growth into the western arm of St. Georges Basin began at 3.5–4 ka with the delta-front sandy silt facies overlying a very thin prodelta mud facies. Seaward extension of the overlying prograded sand facies formed a coarsening-upward sequence that was probably facilitated by the lowering of regional sea-level by about 1.5 m after 4 ka [41]. The fall in sea-level reduced the available accommodation space farther up Wandandian Creek releasing more sediment for delta growth. As the delta prograded into a broader and deeper part of St. Georges Basin its form became less restricted, and the western distributary has formed a typical classic birds-foot delta [37–39,42,44]. The large amount of organic matter in the fine-grained delta facies indicates subaqueous deposition in a low energy environment at water depths similar to or slightly higher than at present [16]. The upper delta floodplains, levees and backswamps partly overlie the lower delta plain subaqueous units described above but elsewhere they directly overlie fluvial sands. These fluvial-dominated areas show a typical fining-upwards sequence, and hosted an extensive vegetation canopy, such as mangrove vegetated shorelines and backswamps with saltmarsh habitats. European modification of the Wandandian Creek catchment (22.1%) has had a limited impact on sedimentation and progradation rates of the delta [15,16]. However, dredging in the Wandandian river channel in the 1970s reduced the amount of bedload transport into St. Georges Basin restricting delta progradation. The effects of modifications such as this means that short term intensive investigations based on remote sensing and GIS analysis are highly recommended in all such areas worldwide. The eco-geomorphic interpretation from this study could assist the Shoalhaven City Council and local landowners on the lower Wandandian Creek floodplains to make informed decisions about the future environmental management of the delta. The findings from this study can be extended locally and globally when considering the Holocene development of coastal lagoons. For example, the widespread occurrence of pyrite- and organic-rich delta-front deposits at relatively shallow depths could lead to the formation of acid sulphate soils if they were drained and oxidized. This would have a large impact on the surrounding environment. This paper has established that remote sensing datasets and GIS analysis, in combination with sedimentological and morphological data, can clearly document the evolution of the Wandandian deltaic eco-geomorphic system as it progrades into St. Georges Basin, southeastern NSW, Australia. The understanding of how the deltaic landforms have evolved in the past can then be used to help establish their probable vulnerability/adaptability into the future. Equivalent analytical methods can be extended to and replicated in similar lagoonal estuaries worldwide.

Acknowledgments: This study is a part of a Ph.D. project of the first author undertaken at the School of Earth and Environmental Sciences at the University of Wollongong. This project has been financially supported by the GeoQuEST Research Centre, University of Wollongong, Australia. Author Contributions: This research forms part of Ali K. M. Al-Nasrawi’s PhD and as such he designed the project, carried out the new research and wrote the draft of the manuscript. Carl A. Hopley provided the results and samples from previous research on the Wandandian Creek delta from which the current study has been developed. Sarah M. Hamylton assisted with advice on the spatial analytical methods used in this research. Brian G. Jones helped design the project, provided assistance with some of the analyses and discussed and edited the manuscript. Conflicts of Interest: The authors declare no conflict of interest. The funding sponsor had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results. J. Mar. Sci. Eng. 2017, 5, 55 20 of 21

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