Photo: Christin Walth
Beach Scraping... is illegal for a reason. Though it's been done at Plum Island & other beaches, Scientists have observed the practice to be ineffective, causing more harm than good. If you understand how the shore works, you can concur with their conclusions:
When waves are large, sand is drawn from the beach to create a long sloping ramp that dissipates wave energy. Without it, waves would hit the beach at full force creating massive amounts of erosion. During times of low wave energy, this shallow area of sand is pushed back up on the shore, oftentimes downstream from where it originated, eventually washing up in front of someone else's house.
The process described above also interlocks & packs sand particles creating a fairly stable substrate (about a solid as sand can be). When you walk on it at low tide, you don't sink in.
So how does beach scraping affect this process? When we beach scrape we do 3 things that make our situation worse:
- First, we take a stable surface & make it unstable by disrupting the interlocked sand grains (about 2 - 3 feet down using heavy machinery) from the near shore shallows all the way to the unsorted pile we create at the barrier dune. Wind & especially water quickly act to move these loose particles away.
- Secondly, through excavation & disruption, we make the once shallow waters near shore deeper, inviting the ocean & its wave energy closer to the very dune we seek to protect. Think back to when you were a child building sand castles. If you dug down in front of your fortress & created a deeper hole, when water finally came in, your walls came tumbling down.
- Thirdly, when we scrape sand we effectively steal it from someone else's home downstream, as well as the public beach.
Scraped sand is an unstable heap of loose sand grains that are easily eroded by wind & water
Water & Wind Naturally Lock Sand Grains in packed & interlocked Layers
Some may argue that 10 inches of scraped sand doesn't matter. But remember, it's being replaced by 10 inches of water. Inviting 10 inches of water closer to your home before a storm is not a sound strategy. Consider that a gallon jug of water weighs 7 lbs., & coincidently is about 10 inches tall. Imagine how many of these gallon jugs fit in the scraped area between Plum Island center & the Columbia way groin. Now imagine playing catch with a gallon jug of water. Move that mass at 10-15 mph in the form of a wave & you can begin to visualize the forces involved.
Finally, because Plum Island has a narrower overall shore (due to the combination of a failed River Jetty & rising sea) there is a new storm high water mark that encroaches upon existing homes. A wall of sand built seaward of that high-water mark will quickly be scoured away when storm waves seek their level.
Scraped Sands Lie Ahead of the New Storm Wave High Water Mark the Day before Sandy Arrived. Photo: Mike Morris
Sandy's High Tide Photo: Mike Morris
Photo: Mike Morris
While beach Scraper's hailed their efforts as a success, Sandy reached the same high water mark in front of the beach scraped homes as she did along homes to the side of the scraped area. However, a noticeable lowering of the beach took place in front of the scraped homes.
While one scraping event probably won't do a lot of harm, and can prevent minor inundations, its widespread use will destabilize the shore giving rise to more problems. Plum Island has been, after all, adulterated with misunderstood interventions. We shouldn't want to employ more of them.