With La Niñas third birthday on the way, can Pittwater’s beaches survive another summer of big swells and excessive rainfall?
It’s the news no one wants to hear, but according to the Bureau of Meteorology, we are officially entering the third year straight of La Niña.
As many would know, these weather systems bring abnormal amounts of rainfall and stir larger swells in the Pacific Ocean.
Triple dip La Niñas are relatively rare – this has only happened three times before since records began in Australia – from 1954 to 1957, 1973 to 1976, and 1998 to 2001.
The Northern Beaches has been no stranger to the effects of La Niña, with costal erosion and flooding devastating many areas over the last two years.
This year, June saw a series of long-range south swells and another damaging East Coast Low, which unleashed chaotic short-range swell and rain from the east.
Collaroy, Narrabeen, Mona Vale, Bilgola, and South Newport all saw significant sand loss, and on a number of occasions, swell surges encroached private property.
Swellnet forecaster, Craig Brokensha, says that the problem is that there hasn’t been enough sand build up over the summer months.
“During winter the beach erodes under the barrage of southerly swells, come spring we switch to smaller swell and northeast winds that will see the sand return,” Craig explains.
The sand both broadens the width and raises the profile of the beach, providing a buffer for when the autumn and winter swells return, something that hasn’t been seen in recent years.
“The problem is that our usual defences are down. The [Northern Beaches] Council needs a solid plan otherwise beachfront properties are going to be sitting ducks,” he says.
While Collaroy has been making headlines for the past year over its controversial seawall input to protect such properties, in South Newport the issue has also escalated over recent months.
Large swells and king tides have seen private infrastructure, such as fences and stairs, from several homes left spilling onto the sand.
Council has been forced to respond by inputting emergency sandbags in front of properties and limiting access to the rockpool and dressing shed.
Angus Gordon, a costal engineer with over 50 years of experience and a general manager for the former Pittwater Council, says that the best long term management plan for our coast is to avoid seawalls in favour of beach nourishment.
After studying costal erosion at beaches like South Newport since 1974, Angus says that there are two obvious solutions to protect our beaches from flooding and erosion.
“The first option is to take the excess sand build-up in our creeks and lagoons and repurpose it elsewhere,” Angus explains.
“One of the reasons why Wakehurst Parkway floods as often as it does, is because it’s chock-a-block full of sand.”
“Development that’s taken place in the Frenches Forest and Belrose region in the sixties and seventies has meant that a lot of sandstone has been reworked and turned into sand. Over the years, the excess has been washed down all the creeks and filled in Middle Creek.”
Angus estimates that there is about three million cubic metres of sand in Middle Creek, more than enough sand to carry out beach renourishment at several beaches and reduce the recurring flooding around Narrabeen Lagoon.
“The other option is to dredge sand from several kilometres offshore,” he says.
“Back in the late seventies I was tasked to look for sand offshore and as a result of about 10 years work, we produced detailed maps of the offshore seabed showing areas that could be dredged without disturbing the environment.”
“There’s a whole pile of things, they [the Council] should have done a long time ago when they haven’t. It’s frustrating, and it’s beyond their competence.”
So, the question remains, what is the Northern Beaches Council going to do differently this year?
Well, according to the recent Council plan to reduce the flooding risk at Narrabeen Lagoon entrance, they will continue dredging accumulated sand at the lagoon entrance, but more often.
The entrance will now be dredged every two years, but a lesser amount of sand will be removed.
Council has also said it will keep using mechanical diggers for ‘emergency breakouts’.
In recent decades, the entrance has been dredged every three to five years with between 30,000 and 50,000 cubic metres of sand removed.
The most recent dredging was between September and December last year, leaving a $1.47 million bill.
Meanwhile, Pittwater ward councillor Miranda Korzy told Peninsula Living in September Council is continuing to word towards a ‘long-term solution’ for Newport that ‘strikes a balance between providing protection to private property while maintaining a maximum width of beach’.
“The problem is that our usual defences are down. The [Northern Beaches] Council needs a solid plan otherwise beachfront properties are going to be sitting ducks”
Swellnet forecaster, Craig Brokensha.
With scientists from the Bureau of Meteorology predicting La Niña conditions will become the new norm along the east coast under climate change, generating these adaptation strategies early are essential to finding the balance between saving residential homes and saving our precious environment.
