Self-described Narooma “tide watcher” Greg Watts believes sea level rise is starting to impact on infrastructure around the Narooma foreshore and suggests planners should be incorporating consideration of sea level rise into construction works.
Eurobodalla Council has responded to his calls noting that sea level rise had been considered in a number of infrastructure projects and that a flood risk management plan was being developed for Narooma Flat and other areas around Narooma.
Mr Watts contributes to the Greenwatch King Tide project, which monitors photo points around Australia during king tide events.
“Climate scientists are saying king tide levels will be the ‘normal’ high tide in 50 years time, and by monitoring king tides now we can see the impacts these tide levels will have towards the end of this century,” he said.
Mr Watts said that his observations of king tides over the last 10 years had shown incremental increase in tidal limit benchmarks around Narooma.
“Each year the tidal inundation seems to be a few centimetres higher. Sea level rise seems to be slow and insidious, but in my observation, it is here,” he said. “There is foreshore infrastructure that has functioned around Narooma for over 60 years that is slowly being compromised by these higher tides.”
The seawalls around the Wagonga Inlet foreshore from Narooma pool to the bridge were a classic example, now being regularly overtopped by these king tides, killing vegetation, causing soil salinity and eroding the banks behind them, so they collapse into the water, he said.
“Sections of the foreshore around the town wharf, Narooma pool, Easts caravan park and Mill Bay are regularly going under. Bank erosion is threatening to compromise the bike path near the bridge,” he said. “The jetties around the inlet, such as at the town wharf and Apex Park, are another example. They are now being regularly overtopped by king tides, often damaging the old infrastructure.
“Repairing this infrastructure to its previous state, as is happening now, is not a solution in the long term. It will simply be overtopped again with the next king tide. There needs to be a strategic plan developed to manage and buffer against this sea level rise in Narooma, and to start putting in infrastructure that will deal with it.”
Eurobodalla Council's director of infrastructure Warren Sharpe said council was absolutely addressing the issue in its longer term construction planning.
“A framework for sea level rise that includes projections based on different greenhouse gas scenarios was completed last year, as well as a tidal and flood analysis for Wagonga Inlet,” Mr Sharpe said.
This study assessed existing flooding and tidal conditions around Narooma, along with flooding under the influence of sea level rise for 2015, 2050, 2070, and 2100, he said.
“These projections are already allowing us to make strategic and well informed decisions about the design of infrastructure and the timing of upgrades and renewals. The recent rebuilding of Riverside Drive is a good example of this,” Mr Sharpe said. “Where practicable we’ve lifted the road level but we’ve balanced this by keeping the sections of the road where overland flows currently go at the current levels, so people’s houses are protected.
“We’ve also applied for NSW Government funding to prepare a flood risk management plan for Narooma Flat and other areas around Narooma.
“This management plan will investigate potential responses to managing flooding and tidal inundation on The Flat, inclusive of sea level rise. Understanding the influence of tide and flooding over an extended period of time will allow us to adapt effectively and lead to a range of controls, such as filling the land and adaptive building design. Some of these measures can be implemented immediately while other controls can be progressive and implemented over extended periods of time.
"It's important to understand that sea level rise is very slow and that other factors can influence infrastructure damage, like storms and high use by the community.
“We do monitor bank erosion, and just recently we've built new rock walls and stairs at Mummaga Lake and Quota Park, in the main to deal with human impacts on the foreshore. So while the work we are doing may not be altogether obvious as climate change preparation, we are certainly using the information from our studies to guide our future infrastructure design and planning.”
The study and the framework are available on council's website at www.esc.nsw.gov.au