EXAMINING ESTUARINE ECOSYSTEMS | Geomorphological factors of the Yarrahapinni wetlands that have exacerbated levels of its future flooding | DYNAMIC MODELLING (55%) REP III 2021 | Carmen Grdosic | a1746203
| contents Title Page...............................................................................................................................................................Front Cover Contents.......................................................................................................................................................................................1 Introduction............................................................................................................................................................................2,3 Proposal.......................................................................................................................................................................................4 Site..................................................................................................................................................................................................5 Process & Techniques Compilation Model 01..............................................................................................................6 Cloud Compare Model 01......................................................................................................................................................7 Process & Techniques Compilation Model 02..............................................................................................................8 Cloud Compare Model 02.....................................................................................................................................................9 Terrain Analysis ....................................................................................................................................................................10 Soil Analysis.............................................................................................................................................................................11 Vegetation Analysis ..............................................................................................................................................................12 Water Analysis...................................................................................................................................................................13,14 Urban Development Analysis...........................................................................................................................................15 Conclusion, Limitations & Improvements...................................................................................................................16 Referencing...............................................................................................................................................................................17 QR Model 01 & Model 02 Links.......................................................................................................................Back Cover Model 01 Link: https://sketchfab.com/3d-models/model-1-yarrahapinni-wetlands-flood-risk-factors-74a9b3a55ab547ee9ff12cc8ba3781d2
Model 02 Link: https://sketchfab.com/3d-models/model-2-yarrahapinni-flooding-2021-2030-2100-a1e9c280395c4bda8a569c4ff8246ec9
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| introduction Yarrahapinni Wetland, formally known as Yarrahapinni Broadwater, was originally a large estuarine wetland which encompassed a substantial portion of the lower Macleay Rover's mangroves, extensive saltmarshes, seagrass beds, and intertidal mudflats (Plan of Management, 2013). However, in efforts to protect nearby towns (South West Rocks) from flooding, flood mitigation works were carried out in 1971 to drain these wetlands and create pasture land. In many locations, such as the selected site where the wetlands have been drained, the predicted benefits in creating this agricultural land have not been eventuated. Instead, the drained land has marginal productivity and the consequential formation of acid sulphate and loss of biodiversity and ecosystems. All of which, have worsened Yarrahapinni's pre-existing major flood risk factors. Correspondingly, impacts from indirect human-induced climate change like sea level rise and coastal erosion, have also contributed to 50% of the wetland's degradation since 1788 (Finalyson, 2000). Thus, both types of human impacts (direct alteration and indirect) have worked in unison to exacerbate these flood risk factors, projecting that the site will be fully submerged by 2100 (Finalyson, 2000). However, by analysing and categorising the site into these major factors, efforts can be made to better understand the landscape's geomorphology and causes for high flood risk. This analysis will help implement better strategies to safely mitigate and build sustainably along these floodplains, so that we can protect and conserve them for our future generations.
2021 NSW FLOODS March flooding of the Macleay River plains pictured: site between South West Rocks and Yarrahapinni wetlands
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Maclea y Arm
Sp en cer s
Yarrahapinni wetlands | Sydney, NSW
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| proposal This analysis aims to provide scientific and modelled reasoning as to the key factors for the wetland's degradation and flooding based on 2009 findings, that can lead to exacerbated future flood levels for the region. To better visualize these findings, a thorough process of LiDAR data research and cloud compare modelling will also be utilized to attain, represent, and illustrate these leading factors. The findings for these factors will be presented as two models; the first illustrating the landscape of the site and major geomorphological features/flood risk factors from 2009, and the second illustrating projected flood levels for years 2021, 2030, and 2100. This process will be key to better visualising these factors to later extrapolate further findings for each factor layer and how each has contributed to exacerbated future flood levels. It is important to understand that both models are to be interpreted in unison, as impacts and trends analysed and made evident in model 1 lead to the increases in flood level of each year in model 2. Researching major factors of the Yarrahapinni wetlands degradation will prove useful for; the NSW government to install more specific conservation policies, marine scientists to better understand the damaging effects of climate change on estuarine systems, and for the public to better educate themselves on the importance of protecting our wetlands from the effects of human induced climate change. The ultimate goal for this research proposal is to encourage all round increased awareness for flooding factors and better sustainability practices and lifestyles in greater Sydney. Wetland degradation and flood risk is often caused by multiple drivers, some of which are site based, while others are regional or global in scope. This makes it difficult to reverse, even where social and institutional support is strong (Plan of Management, 2013). To better analyse causes of flooding surrounding the Yarrahapinni Wetlands, the Yarrahapinni/South West Rocks site will be categorised into chosen drivers will form the foundation for this analysis. They are as listed alongside:
FLOOD RISK FACTORS FOR ANALYSIS:
1. TERRAIN & TOPOGRAPHY a. Elevation and height maps b. Soil Acidity, sulphate/phosphate levels and salinity 2. SOIL a. Soil classifications, types & permeability b. Drainage patterns and problems 3. VEGETATION a. Vegetation Systems loss b. Soil Fertility 4. WATERBODY a. Amount of embankment erosion/coastal erosion/river erosion/year b. Rainfall (in mm) increases c. Implemented flood mitigation interventions 5. URBAN DEVELOPMENT & INTERVENTION a. Increase in population of site/town of South West Rocks b. Increase in number of residential dwellings within site c. Land Use Mapping
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| site location
location: coordinates -30.894646, 153.017283
The site for analysis is located on the western outskirts of the town of South West Rocks. This site is rich in data, has many varying soil types, and visually, has high levels of embankment erosion. This particular site also has an extensive history of flooding as well as some of the highest flood levels ever recorded being at 6.61m in 2021. Visually, the site consists of many flood risk factors that are already evident from satellite view. These include; urbanisation and urban expansion of a town that continues to grow with its population, vegetation loss or the introduction of invasive species, and embankment erosion and varying waterlines that are marked on the sediment. These factors will be analysed further and related back to flood risk susceptibility.
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| model 01 process compilation
Data Collection from ELVIS
CC file converted to RGB & Shadvis applied to create base layer
Scalarfield & classification organise file by colours
LiDAR Point Clouds Imported into CloudCompare as LAS
Satellite imagery sourced from GoogleEarth
Satellte imagery georeferenced against LiDAR point clouds using QGIS plugin Quickmap ESRI-Satellite
QGIS LASCOLOR plugin combines geoferencing with pointcloud LAS file
Filter by value
ShadeVis and illuminance
Custom RGB applied
Transformation of 2000 points on Z-axis
Each layer cloned and processes repeated for a toal of 5 times for each floodrisk layer
KEY Data collection and satellite imagery sourcing QGIS processes
Model finalised and uploaded to Sketchfab
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CloudCompare processes
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| cloud compare model 01 06 | URBAN DEVELOPMENT
05 | WATERBODY
04 | LARGER VEGETATION (TREES)
03 | SMALLER VEGETATION (LANDCOVER & SHRUBS)
02 | TERRAIN & ELEVATION
01 | SITE BASE
Axonometric of site and its floodrisk factors using LiDAR data from the 2009 Yarrahapinni region from ELVIS
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| model 02 process compilation Sourced for years : 2021 2013 2100 Data Collection from ELVIS
CC file converted to RGB & Shadvis applied to create base layer
LiDAR Point Clouds Imported into CloudCompare as LAS
Projected inundation sourced from plas.io
QGIS LASCOLOR plugin combines geoferencing with pointcloud LAS file
Satellte imagery georeferenced against LiDAR point clouds using QGIS plugin Quickmap ESRI-Satellite
Process repeated to source and represent data for 2030 flooding layer and 2100
Transformation of 2000 points on Z-axis
Model finalised and uploaded to Sketchfab
>
KEY Data collection and satellite imagery sourcing QGIS processes CloudCompare processes
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| cloud compare model 02
03 | PREDICTED FLOODLINE YEAR 2100
02 | PREDICTED FLOODLINE YEAR 2030
01 | CURRENT WATERLEVEL 2021
Axonometric of site and its floodlines across current years and predicted years of 2030 and 2100 using LiDAR data from the 2009 and data from estimated future PLAS.IO inundation (flooding) data
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02 | terrain analysis ELEVATION & SLOPE Conducted sectional analysis of the site visually indicates that the site is relatively flat in its terrain. This is reinforced by comparing the section to an elevation map from ELVIS. Both results indicate that the selected site as well, as the Yarrahapinni Wetland-Western South West Rocks, displays relatively gentle/level terrain, with majority of the elevation for the area comprising of only 22-33 metres above sea level (Geoscience Australia, 2021).
Figure #1 Elevation and height heat map (eSPADEv2.1, 2021)
It is known that any low-lying area adjacent to rivers (such as the selected site) is far more likely to experience severe flooding than more elevation areas. Thus, it can be determined that the site's incredibly low elevation is a major contributing factor towards the recent severe flooding events, including high flood lines and flood risk. Conducted terrain section analysis using CloudCompare
SOIL ACIDITY (SULPHATES & CALCIUM CHLORIDE)
Figure #2 Soil acidity pH (eSPADE v2.1, 2021)
Additionally, as salinity increases over time, wetlands become degraded, endangering wetland species and decreasing biodiversity. Where sulphate salts are present, there is an increased risk of acid sulphate soil formation (NSW Environment, Energy and Science, 2021). Acid sulphate soils are natural sediments that contain iron sulphides (NSW Environment, Energy and Science, 2021). When disturbed or exposed to air these soils can release acid, damaging built structures and harming or killing animals and plants. As analysed, the chosen site displays highly acidic pH levels ranging between less than <4.0-5.0 (eSPADE v2.1, 2021). This is then reiterated in the high probability of acid sulphates present in the soil, having a risk factor of H0 to H1 (high probability on surface levels and 1m below the ground (eSPADE v2.1, 2021). Consequently, these incredibly high acid sulphate levels and salinity impact the growth of many vegetation systems that are crucial to maintaining flood levels. High acidity make the conditions of the soil unbearable for vegetation, degrading these wetland ecosystems. High acid sulphate levels destroy vegetation, reducing the amount of water that is absorbed and transpired by these plants. If this water is left unabsorbed, flood levels will rise. It can be then be determined that this high presence of acid sulphates and low acid levels are a crucial driver towards the site's high flood risk.
Figure #3 Acid Sulphate Risk Mapping (eSPADE v2.1, 2021)
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02 & 03 | soil analysis SOIL CLASSIFICATION & PERMEABILITY Different types and classifications of soils have different densities and qualities that create altering rates of percolation and absorption. Factors in which, impact flood level. According to the data gathered alongside (eSPADEv2.1, 2021), the major soil categories that define the site are: rudosols, hydrosols, podosols, and kurosols. However, it can visually indicated that hydrosols are the more dominant soil type. When analysing the characteristics of hydrosol soils it can be noted that hydrosols are permanently wet soils, and have great saturation, often lasting 2-3 months (ASC - HYDROSOLS, 2021). This saturation is a result of extremely low soil permeability, leading to poor soil drainage (ASC - HYDROSOLS, 2021). Low soil permeability is a dominant driver in high flood levels, as if water is struggling to be absorbed by soil into aquifers underground, it sits and spreads on top of the topsoil.
Figure #4 Soil types & classification (eSPADEv2.1, 2021)
DRAINAGE PATTERNS & DIFFICULTIES Poor permeability and absorption from dense or saturate soil types can lead to poor drainage patterns and difficulty for drainage on the site. In the 1970s, extensive dredging (every 12-18 months) of the Yarrahapinni catchment was undertaken to deepen and widen drains and form new catchments to improve the drainage of this area (Wilkinson, 2014). However, the exclusion of tidal inflow and the dredging or lowering of the water table by drainage resulted in severe deterioration of the wetland ecology, hydrology, geomorphology and chemistry (Wilkinson, 2014). Damage of machinery used for this dredging is even evident in the data shown alongside. Dredging had occurred where regions are highlighted red, orange and yellow. The most poorly draining areas surround the embankment of the site, and this in turn, can lead to rising flood levels along embankments, where urban developments are located. For instance extremely poor drainage is located near the Rocks Fishing Charters, located on the western outskirts of South West Rocks, with gallons of water absorbed less than 0-0.5. Such high levels of poor drainage this close to urban development increases the site's flood risk drastically. Figure #5 Map illustrating the poor drainage patterns of the Yaarrahapinni wetlands (eSPADEv2.1, 2021)
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04 | vegetation analysis VEGETATION LOSS & SOIL FERTILITY Vegetation loss is a significant factor flood risk, as without extensive vegetation cover, excess water is unable to be absorbed and transpired. Loss of tidal inflow and lowering of the water table by drainage has the vegetation within the wetlands to completely change: the mangrove and salt marsh areas were drastically reduced (Wilkinson, 2021). In addition (as previously mentioned) lowering the water pH caused denuding of existing vegetation and thus, the formation of extensive areas of acid sulphate scalds (vegetation diseases from high acidity) (Wilkinson, 2021). For instance, the isolated remnants of trees or clumps of mangroves evident in Figure #8 were a dominant feature before flood mitigation works, but now are covering less than 1 hectare (SWC, 1999). Additionally, coastal saltmarshes also have a very limited extent at 4 hectares remaining, and are now restricted to the southern half of the site (SWC, 1999).
Figure #6 Soil fertility mapping (eSPADEv2.1, 2021)
By understanding and acknowledging causes for this vegetation loss, it is evident that loss of mangrove and saltmarsh systems have increased the site's risk of flooding over the years, as scolding decreases the amount of water absorbed and transpired by these ecosystems. It is also important to note that vegetation loss from 1997 to present (2021) has only been expected to increase, given the increased presence of high acid sulphate levels and the projected flood line levels for years 2030 and 2100.
Figure #7 Vegetative Cover 1942 (Wilikinson, 2014)
Figure #8 Vegetative Cover loss 1997 (Wilikinson, 2014)
Figure #9 Remnants of diseased and dying mangroves
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05 | water analysis COASTAL EROSION & CLIMATE CHANGE Coastal erosion from sea level rises have worked to increase embankment erosion that encapsulates the selected site. Due to climate change, a sea level rise of 90 centimetres is expected by the end of the century and will continue to rise in the following centuries (DECCW, 2010). As analysed in the flooding satellite views, the site as well as the Yarrahapinni region are expected to be fully submerged by 2100 (DECCW 2010). This data is supported by 2009 findings of embankment erosion recorded of the site. The site has experienced extreme erosion levels raging rates from 200-500 hectares for areas surrounding urban development along the river to rates of 1000-2000 tonnes per hectare per year for more developed areas (eSPADEv2.1, 2021). Thus, this drastic levels of erosion will continue to worsen, and will damage developed areas the most, increasing flood risk to extreme levels. Figure #10 Embankment Erosion Map (eSPADEv2.1, 2021)
YEARLY RAINFALL Storm surge flooding from tropical storms (like in 2009 in Yarrahapinni) result in the accumulation of excessive amount of water traveling inland to wetlands. A 200mm increase (26.6%) from 2009-2011 exacerbates the flood level for the site (Fisherman's Reach) (Wilkinson, 2014). This increase in rainfall is increasing with the effects of climate change and is thus, a contributing factor towards the projected high flood levels (2030-2100) and risk of the site.
FLOODING MITIGATION
Fisherman's reach (site)
Figure #11 Incremental monthly rainfall across a 2 year period (2009-2011) (Wilkinson, 2014)
Between 1969 and 1971 significant flood mitigation works were carried out throughout on the north-western areas of the selected site. These works included closing channels between the mangrove islands with 800m rock levee banks (Wilkinson, 2014). A floodgate structure was also implemented that allowed outflow, but however, stopped inflow. Extensive dredging was also carried out in catchments to deepen and widen drains to form new channels in efforts to improve drainage (Wilkinson, 2014). Consequently, the exclusion of tidal inflow and the lowering of this water table resulted in severe changes to the hydrology of the site's landscape. Thus, this disruption and manipulation of Yarrahapinni's natural hydrological systems halters natural flooding patterns, which in turn, massively increases flood risk of the region and selected site. Hydrological changes result in flood line surges, which are highlighted in the conducted projected flood line mapping below. Figure #12 Location of Flood mitigation Systems remaining from implementation in 1970s
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2021
2030
2100
PROJECTED FLOOD LEVELS PLAS.IO projected flood levels for current year (2021), 2030, and 2100
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06 | urban analysis LAND USE MAPPING More developed areas contain tarmac, cement, pavement and tile flooring, which prevents percolation and is by no means a permeable surface for the absorption of water runoff. According to eSPADE data, developed areas consist of urban and intensive areas and intensive animal and plant production (eSPADEv2.1, 2021). As the site is located in a basin with relatively low elevation and high flooding susceptibility, developing on these floodplains is highly dangerous. When additional obstructions like cement are added on top of soil that already has low permeability, flood risk skyrockets. Any water that is trapped on this developed surface spread to urban developments, flooding the towns. This is why, population increases in South West Rocks towards 2030, so does the flood level (expecting to be completely submerged). Figure #13 Land use mapping and typologies (eSPADEv2.1, 2021)
PROJECTED RAPID POPULATION GROWTH
Figure #14 Data illustrating population and dwelling growth & statistics (Populations Projections Report, 2009) (2016 Census QuickStats, 2016)
Population growth heightens impacts of human-induced climate change, which in turn, increase the sea level which exacerbates coastal flooding, flood level and risk. Thus, population growth, climate change, and flooding are all interconnected and impact each other (DECCW, 2010). These findings are supported from data sourced from the 2009 Populations Projection Report of Kempsey Shire Council and the Australian Bureau of Statistics, which indicate that South West Rocks is expected to endure a population growth of approximately 29.3% between 2021 and 2031 (next decade) (Populations Projections Report, 2009). Additionally, data from these sources also illustrate that as a result, the dwelling and infrastructure count is predicted to increase by 46.6% (2016 Census QuickStats: South West Rocks, 2016). This rapid growth of urban development places pressure on the landscape, as additional infrastructure places pressure on the already-highly risked floodplains of the site. The projected 2030 flood line supports these findings as with the increase of the projected population of South West rocks comes the expanding flood levels, enveloping majority of the town by this year alone.
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| conclusions, limitations & improvements CONCLUSIONS
In summary, it has been made evident that there a range of drivers or factors that lead to high flooding risks within the Yarrahapinni region and the selected site of the western outskirts of South West Rocks. These factors were made visually apparent through thorough scientific modelling using LiDAR point clouds, QGIS and CloudCompare software, which also aided in the clear organisation of these major drivers. This process was applied to two model displaying how factors of flood risk (in model 01) have increased projected flood levels (in model 02) for years 2030 and 2100. Extrapolation and additional analysis of each layer indicated that there are findings of flood risk factors that in turn, cannot be visually represented but still massively contribute to the heighten flood risk of the region throughout history. It was discovered that the selected site consists of flat terrain, impermeable soil with high levels of acid sulphate, which had led to vast loss of crucial saltmarsh and mangrove systems that previously offered the site flood protection, contributing to heightened flood risk . It was also noted that population growth of the town of South West Rocks of the selected site is indicative impacts of human-induced climate change, which increases coastal flooding and wetland flood risk. Increased population growth also meant that increases projected urban developments only added to the problem, worsening all factors previously mentioned, creating an omnipresence of high flood risk that would later see the town enveloped by 2100.
LIMITATIONS & IMPROVEMENTS
Although all data sourced eventuated to a succinct and transparent model showcasing all drivers of flood risk appropriately, limitations had been encountered that could have been improved if repeated. Initially, LAS files, DEM's and PointClouds sourced from ELVIS were considered somewhat outdated and could have been more accurate and representative of the current conditions and flooding that occurred at the beginning of April 2021 instead of flooding from 2009. Data only existed from the year 2009 and was thus, limiting for this research as it aimed to show trends or patterns over time. However, as these disastrous flooding events were recent, this data was not yet collated by ELVIS. Other limitations also endured throughout the QGIS georeferencing process in regard to issues surrounding TIFF file exportation, however these were later resolved using satellite imagery from an external source (GoogleEarthPro). Furthermore, errors with LAS file importation from ELVIS were encountered and only select number of files seemed to load without the presence of errors. Improvements including having access to data from two years (minimum) would have showcased trends more clearly but however, did not limit the additional layer findings indicated throughout this research.
NSW | Yarrahapinni Wetland/South West Rocks Western Outskirts
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| referencing Clw.csiro.au. 2021. ASC - HYDROSOLS. [online] Available at: <https://www.clw.csiro.au/aclep/asc_re_on_line/hy/hydrsols.htm> [Accessed 11 April 2021]. DECCW (2010) NSW Climate Impact Profile: The impacts of climate change on the biophysical environment of New South Wales. Department of Environment, Climate Change and Water. Available from: http://www.environment.nsw.gov.au/climateChange/RegionalImpactsOfClimateChange.html Environment.nsw.gov.au. 2021. eSPADE v2.1. [online] Available at: <https://www.environment.nsw.gov.au/eSpade2Webapp> [Accessed 6 April 2021]. Finalyson, C., 2000. Loss and Degradation of Australian wetlands. [online] Environmental Research Institute of the Supervising Scientist. Available at: <https://www.environment.gov.au/system/files/resources/ecb4f5e8-e7c7-4b38-a070-6c4fbc17b834/files/ir351.pdf> [Accessed 6 April 2021]. Ga.gov.au. 2021. Digital Elevation Data | Geoscience Australia. [online] Available at: <https://www.ga.gov.au/scientific-topics/nationallocation-information/digital-elevation-data> [Accessed 6 April 2021]. Kempsey.nsw.gov.au. 2009. Population Projections Report April 2009. [online] Available at: <http://www.kempsey.nsw.gov.au/development/pubs/population-projections-report-2009.pdf> [Accessed 6 April 2021]. NSW Environment, Energy and Science. 2021. Salinity. [online] Available at: <https://www.environment.nsw.gov.au/topics/land-andsoil/soil-degradation/salinity> [Accessed 6 April 2021]. Quickstats.censusdata.abs.gov.au. 2016. 2016 Census QuickStats: South West Rocks. [online] Available at: <https://quickstats.censusdata.abs.gov.au/census_services/getproduct/census/2016/quickstat/SSC13600?opendocument> [Accessed 6 April 2021]. SWC (1999) Yarrahapinni Wetland Research Project. A report prepared for Yarrahapinni Wetlands Reserve Trust by SWC Consultancy, a division of Shortlands Wetlands Centre Ltd, Newcastle Wilkinson, K., 2014. Chapter 1. [online] Rune.une.edu.au. Available at: <https://rune.une.edu.au/web/bitstream/1959.11/16918/9/open/SOURCE04.pdf> [Accessed 11 April 2021]. Yarrahapinni Wetland National Park, 2013. Plan of Management. [online] pp.6, 14, 29. Available at: <https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Parks-reserves-and-protected-areas/Parks-plans-ofmanagement/yarrahapinni-wetlands-national-park-plan-of-management-130495.pdf> [Accessed 6 April 2021]. LiDAR Data sourced: https://elevation.fsdf.org.au/
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sketchfab QR codes
model 01 factors
model 02 flooding