Parallel 3 – High rise, high risk: how sea level rise will affect Australia’s coastline

Chair: Megan Saunders


CANUTE: The Sea Level Calculator (904)

Steve George 1

  1. Antarctic Climate & Ecosystems CRC, Hobart, TAS, Australia

In a world of rising sea-level, coastal infrastructure will need to adapt to remain viable. Canute is an online Decision Support Tool that provides a suite of applications to quantify the impact of present-day and future sea-level scenarios on the Australian coastline. The primary impact, the magnitude of
extreme events, is presented by either a range of statistical products, or in the form of an allowance (i.e., the amount by which the height of coastal infrastructure needs to be altered to cope with climate change). The analysis combines storm-surge modelling products with the latest IPCC AR5 climate predictions.

In addition to the still-water level, waves also have an impact on coastal regimes. An application to calculate the impact of waves on the Australian coast (in the form of setup/runup) is provided. The tool uses data from the NOAA Wavewatch III model. For soft shorelines beach recession will, in the future, be a confounding factor. Canute presents a front-end to extensive beach-recession modelling work (which moves beyond the simple Bruun rule). For Tasmania, this is augmented by an associated project (TASMARC) which monitors shoreline positions and beach profiles. Preliminary tools to calculate the financial impact of rising sea-level are also presented.


 

Interdependency of tropical marine ecosystems in response to climate change (905)

Megan Saunders 1 2 , Javier Leon 1 3 , David Callaghan 4 , Chris Roelfsema 3 , Sarah Hamylton 5 , Chris Brown 1 2 , Tom Baldock 4 , Ali Golshani 4 , Stuart Phinn 1 3 , Catherine Lovelock 1 6 , Ove Hoegh-Guldberg 1 , Colin Woodroffe 5 , Peter Mumby 1 2

  1. The Global Change Institute, The University of Queensland, St Lucia, QLD, Australia
  2. Marine Spatial Ecology Lab, School of Biological Sciences, The University of Queensland, St Lucia, QLD, Australia
  3. School of Geography, Planning and Environmental Management, University of Queensland, St Lucia, QLD, Australia
  4. School of Civil Engineering, The University of Queensland, St Lucia, QLD, Australia
  5. School of Earth and Environmental Sciences, The University of Wollongong, Wollongong, NSW, Australia
  6. The School of Biological Sciences, The University of Queensland, St Lucia, QLD, Australia
Sea-level rise drives the redistribution of coastal ecosystems. Ecosystems are linked within landscapes by the physical and biological processes they mediate. In connected landscapes, the response of one ecosystem to sea-level rise could have influence neighbouring systems. In shallow tropical coastal marine ecosystems, coral reefs shelter lagoons from incoming waves allowing seagrass meadows to thrive in lagoons. Deepening water over coral reefs from sea-level rise allows larger, more energetic waves to traverse into the lagoon, deteriorating conditions for seagrass. Coral reef growth to maintain relative water depth could potentially mitigate negative effects of sea-level rise on seagrass. We conducted an interdisciplinary field and modelling study at Lizard Island, Great Barrier Reef, where shallow seagrass meadows thrive inshore of a barrier reef. We predict negative effects of sea-level rise on seagrass before mid-century under moderate to high greenhouse gas emissions scenarios and given reasonable rates of reef growth. This is because rates of vertical carbonate accretion typical of modern reef flats, up to 3 mm·yr-1, appear insufficient to maintain suitable conditions for reef seagrass. This is the first quantitative prediction of interdependencies between ecosystems in response to climate change. The results highlight the need for landscape scale management plans which consider the interdependent responses of multiple ecosystems to climate change.

Different strategies, different communities: Adaptation to sea level rise and surge in Torres Strait (906)

Kevin Parnell 1 2 , Scott Smithers 1 2

  1. Centre for Tropical Environmental and Sustainability Sciences, James Cook University, Townsville, QLD, Australia
  2. School of Earth an Environmental Sciences, James Cook University, Townsville, QLD, Australia
Surge events at periods of high tide will become more problematic in Torres Strait communities with sea-level rise. The focus to date has been on the north-western island communities of Saibai and Boigu and the coral cay island communities of Masig, Warraber and Poruma. The future for ‘high-island’ communities where sea level rise will impact infrastructure and other important sites on low and narrow coastal strips (particularly Mabuiag, Erub and Mer) has been given less consideration. Community specific issues, adaptation options, and the results of community consultation processes undertaken over the period 2006-2013 are presented. For Boigu and Saibai, the cost of protection of the entire community area is likely to be prohibitive, and a model that reduces the community footprint is presented. The cay island communities (Masig, Warraber and Poruma) all have high areas where community infrastructure needs to be concentrated in the future, and adaptation can be achieved through careful long-term planning and investment. Some high island communities must re-focus activities away from low coastal strips. Most high island communities will have localised but solvable problems. Barriers to effective community-based adaptation to sea level rise are identified, and include planning processes, infrastructure provision, funding and land ownership.

Exploring the relative importance of Changing Sea Level versus Changing Wave Climates for the next 30 years along the East Coast of Australia. (907)

Ron Cox 1 , Kristen Splinter 1 , Ian Turner 1

  1. UNSW Australia, UNSW Australia Sydney, NSW, Australia
In recent years, much of the focus on the impacts of climate change on the world’s sandy coastlines has been on the slowly varying process of sea level rise. A simple Bruun-rule approach suggests that as sea level rises, the beach profile must keep up and this is done by eroding the upper dune system and placing that sand in the nearshore region. While sea level has risen along the Sydney coastline in the last 4 decades, there is no discernable long-term trend in the nearly 4 decades of beach profiles at Narrabeen-Collaroy. By contrast, this beach, like many others along this stretch of coastline is impacted by large storms, such as the 1974 events, or more recently the 2007 Pasha Bulka storm. These storms are capable of eroding beaches 50m+ in a period of several days. Recovery of these events can take between weeks to years, depending on the level of the storm. As part of the NSW Climate Adaptation Research Hub, here we will present findings using an existing, calibrated shoreline evolution model to examine the relative storm demand and recovery rates associated with the estimated ARI storm events as detailed in Shand et al. (2010) “NSW Coastal Inundation Hazard Study: Coastal Storms and Extreme Waves” and compare those to projected sea level rise trends over the next 30 years.

Estimating the impacts of beach erosion and cyclones on coastal property values: A Queensland case study (908)

Clevo Wilson 1 , Boon Lee 1 , Walter Hein 1

  1. Queensland University of Technology, ., QLD, Australia
Owing to a changing climate, research shows that natural hazards such as floods and tropical cyclones are becoming more frequent. In this paper, the impacts of natural hazards, particularly beach erosion and cyclones are examined. In Australia, approximately 85% of the population resides along its coasts. Due to the detrimental effects of beach erosion and cyclones, it is hypothesised that these impacts would negatively impact on the values of Australia’s coastal residential properties. Employing Hedonic Pricing (HP) modelling, the paper attempts to quantify the impacts of beach erosion and cyclones on coastal property values in Queensland. Selected properties from Sunshine Coast and North Queensland subject to beach erosion and cyclones respectively are selected. The results show that while there was minimal impact on beach erosion on Sunshine Coast’s coastal property values, the impacts of intense tropical cyclones on residential property values in Northern Queensland was significant. The results obtained from both analyses provide a justification for policymakers to understand the risks of beach erosion and cyclones to Queensland’s coastal communities. Understanding these risks will enable policymakers to adapt and mitigate the damage from coastal hazards. This research could help inform adaptation and mitigation strategies