A CRITICAL REPORT ON THE RMVB SHORELINE CONCLUDES: Revetments: Doomed to Fail and Doomed to Destroy the Beaches
Last night on July 23rd, Peter Zuzek of Baird Engineering gave a very strong, intelligent, sensitive, scientific and lay term comprehensible presentation regarding Shoreline Protection at a meeting at the Sports Centre for the RMVB community at large.
(Baird has been hired by the RMVB as in independent and unbiased source to analyze the possible causes for our erosion issues and to propose possible solutions for them. They have been actively working since October studying our particular shoreline dynamics, content and complexities.)
One of the first things Mr. Zuzek said to start the evening was that “We (Baird) are here to try and remove the emotion and focus on the science.”
After listening and contemplating his factual and science based reports, combined with the discussions following, two things became emphatically clear by evening end.
In his companies independent and unbiased opinion:
1. Revetments in front of sand beaches will ultimately destroy the beaches in front of them.
2. Revetments on the banks in the RMVB will eventually, over time, fail. They will not be able to maintain their capacity to protect the shore over the longer term.
(Note: This information is coming from a company that builds revetments all over the world. They fully agree that these structures do serve their purpose when they are built and maintained properly in the proper environment for them to function and succeed. There is a proper place for them to be built and to effectively work. However, it is their opinion, the shorelines of the RMVB is not one of those places if our goal is to protect the beaches we currently have. “We can build them, but you don‘t want them in front of your public beach.”)
Mr. Zuzek made a critical point very clear (through a very effective slide presentation)that stabilizing the bank –through rip rap or revetments — does not, nor will not completely stop all the erosion taking place. Nor will it help the beach in front of it.
Erosion, by the way, that is a completely normal and natural occurrence.
He showed that the problem with a rip rap or revetment is that it denies the replenishment of the sand to the beach that occurs through natural erosion from the cliffs and banks. (This is how the greatest amount of sand comes to our beach in conjunction with a smaller amount from the currents.)
What many people are not aware of is that through the soil samples of the area they have been collecting it has become clear that approximately 100 to 150 meters out from the beach shoreline the sand stops and the bottom of the lake is then clay. Thus the actual “sand area” under water that the beach can draw from is relatively small. There is not nearly as plentiful and abundant an amount of sand in the lake bottom as many have assumed.
More importantly, once you get to the clay area, erosion actually takes place there too.
It was then pointed out to the surprise of many that very much the same erosion process happens at this point — where sand meets clay underwater — as it does on the banks where we can see it happening!
This underwater erosion is called downcutting. (Again, all a natural occurrence.)
It turns out revetments are actually doomed to cause two disasters.
First, a revetment problematically stops the natural process of erosion of the banks from which beach sand replenishment actually comes. Leading to an eventual scouring and removal of the beach before them.
Secondly, all the while, the revetment then actually increases the irreversible downcutting under the water.
This unseen and now increased erosion continues underwater until the revetment itself, over time, becomes unstable and is also destroyed. Literally falling back into the water as the sand is completely lost under the water and the delicate clay underground erodes as well.
Eventually, without exception, the clay base becomes unstable, causing the failure of the entire revetment or rip rap structure.
In Mr. Zuzeks own words.
“In the RMVB it is A FACT that a revetment will eventually fail and fall into the lake.”
“It is A FACT, that revetments will accelerate the downcutting.”
Thus, in no uncertain terms: If revetments go up, the beach sand will disappear.
Over time, so will the revetments.
A loss on all counts.
Mr. Zuzek commented during the evening “I can reaffirm that revetments will destroy the beaches. I can guarantee that will happen.”
So in the end it becomes very clear that the RMVB community and its Council needs to make clear, decisive and bold choices from now on regarding anything being built on our shorelines. Particularly when it comes to rock rip rap and revetments.
It is our civic and moral duty to protect these beaches not only for the present but for all the generations to come.
We need to ask ourselves before anything is ever allowed to be built on the shorelines again, like that which has occurred on Arthur: What are the consequences of a structure built on our shorelines? How will it impact it? (We can no longer pretend Victoria Beach is somehow “special” and unlike anywhere else on earth. The Baird study makes it abundantly clear what type of irreparable damage revetments can and likely will cause. )
We must ask: Does a proposed structure maintain and conserve our public spaces for generations to come? (As per our RMVB Development Plan which clearly stipulates is a main priority, aim and goal of the community at large).
Most importantly we must ask: Does the structure — intentionally or not –go against those goals?
The RMVB has a lot of things to consider in the days, months and years ahead and one thing has become clearer and clearer, time and time again, over the past year: that science says revetments are not the solution for trying to protect property in front of public sand beaches.
It is that plain and that simple. Confirmed yet again, this time by an independent source hired to particularly look at our own situation in the RMVB.
It seems reasonable after the Baird presentation that it is finally time for the council of RMVB to unanimously accept the science. To heed to the will of the large majority that seems to accept that science.
As Mr. Zuzek stated: “The time has come that the RMVB takes active and permanent intervention as this is the only way to protect front row homes and local beaches.”
The Council must accept its duty to protect the unique character and beauty of our public area beaches and place it as the number one priority from this day forward.
That from this day forward, future time, resources and efforts would be better spent on investigating other ideas and solutions — and hopefully implementing them — to deal with erosion issues facing property owners.
But that revetments, in front of public sand beaches and public spaces, should be ultimately denied from this day forward.