Plum Island Erosion

Plum Island Erosion (14)

Much faith, effort & money was wagered on a favorable outcome for the Dredging & Beach Nourishment project that commenced in September of 2010. Though it was regarded as a short term solution to Plum Island's erosion woes, most didn't think the term of relief would be so brief.  The River Jetty Breach should have been repaired first, and then the beach nourished with the dredge spoils. With the breach still passing sand to Plum Island Point & the Merrimack River, these dredged materials quickly eroded away. Think of it like trying to fill a bucket of water to the rim - but there is a hole along the side. No matter how much water is added (& in the case of Plum Island, it is sand) one can never keep the bucket full. In the effort to stave erosion, the cart has been placed before the horse. Though Beach nourishment activities can buy homeowners time, they are temporary, very short term, expensive solutions.

"Results of the 2010 River Dredging & Beach Nourishment Project"

Viewing Instructions: Click lower right corner to expand viewing size. Click to advance slides & animations

Custom Flash - Free Version

Tuesday, 05 March 2013 20:54

Hard Structures Seawalls & Geotubes

Written by

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

Tuesday, 05 March 2013 20:41

Beach Scraping

Written by

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:

  1. 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.
  2. 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.
  3. 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

Scraped sand is not layered its an unsorted heap

Water & Wind Naturally Lock Sand Grains in packed & interlocked Layers

Layerd Dune 116

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

2 Scraped Sand ahead of storm high water mark 017

Sandy's High Tide Photo: Mike Morris

3 Sandy Arrives 044

4 Scraped Area After Sandy 076

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.

Tuesday, 05 March 2013 13:10

Short Term Erosion Control Measures

Written by

Plum Island has employed short term erosion control measures that include beach nourishment, beach scraping & the use of sea walls in the form of geo-tubes or coir sandbags. Let’s look at these practices, their caveats & how well they performed.

"The results of the 2010 River Dredging & Beach Nourishment Project"

"Beach Scraping" 

"Hard Structures Sea Walls & Geotubes" 

 

Tuesday, 05 March 2013 12:55

About the Author

Written by

About the Author

by Frank Cataldo

"When you're curious, you find lots of interesting things to do."~ Walt Disney

When Mike Morris was just a boy his dad instilled in him a curiosity of the world around him. His dad not only taught him about the natural world, its creatures & its cycles, but also the aspects of things mechanical. This curiosity grew into a diversity of interests and a career that has touched the fields of Biomedical Science, Marine Biology, Healthcare Management, BMW race cars, Alternative Automotive Energy Technologies and more relative to Plum Island, Oceanography, Climate Change & Sea Level Rise.

Mike's interest in Oceanography is rooted in the sport of surfing, a lifelong passion since the age of 11. He was described by author Andrea Fox in a North Shore Magazine feature article on Plum Island Erosion, as a "Wave Enthusiast". The sport has lured Mike to surf spots around the globe. He's surfed breaks not only here in New England, but also on the Outer Banks of North Carolina, Puerto Rico, the British Virgin Islands, Hawaii and also the Pacific coasts of Mexico & Costa Rica.

Planning a successful surf vacation, whether it is a few days in New England or a week somewhere more exotic, requires successful surf forecasting. To this end Mike studied Physics, Meteorology and Oceanography while pursuing a degree in Biology and a MS in Public Health & Business from the University of Massachusetts, Amherst. With the advent of the internet & the declassification of Military wave forecasting models in 1996, the task of accurately forecasting surf became much easier and more accurate. Today, wave propagation models can predict the arrival of a distant swell within a 6 hour window of time. Mike has studied these models daily since1996 over the last 17 years relating meteorology to surface winds & then wave generation and propagation. The ultimate verification of a model's forecasting ability was to see the swell "light up" offshore weather buoys, and ultimately arrive at the beach with the size & period  forecasted. Mike Currently provides Surf Forecasting services through his company Northeast WaveWatch.com for northernsurfer.com & PlumIslandSurfco.com. Mike is also actively involved in sea-level rise planning & adaptation for local communities.

So why did Mike complete a study on Plum Island Beach erosion? Mike and his wife Jen Wright own a home on Plum Island. In 2006, Jen was elected to the position of selectman for the town of Newbury. During her term, beach erosion at Plum Island had accelerated and became a great concern. Understanding Mike's knowledge of oceanography, she asked him to attend some of the early meetings about the problem and make sense of the science. What became apparent was that there were many theories, very little science, and a plan in the works to solve a problem that no one had taken the time to unravel & understand.

Realizing that it's impossible to solve an ill defined problem, Mike set off with camera in hand, photographing the beach, its dunes, the rock groin structures and the Merrimack River mouth. His curiosity motivated him to understand what was happening along the shore. To observe and quantify changes along the Plum Island shore, he also researched historical nautical charts dating from present day back to the pre-revolutionary war era. He analyzed some 90 years of Massachusetts CZM shoreline change data as well as 15 years of satellite imagery.

He charted the changes Plum Island had undergone and related these changes to events in Plum Island history. To better understand the forces (wave energy) driving Plum Island's sand migration, Mike sifted through some 7000 hours of actual wave buoy data where he discovered that wave direction during Northeast storms changes as the storm evolves, and so isn't always only from the Northeast. In fact, the most powerful waves impacting Plum Island's shore almost always originate from far offshore, to the east and southeast - it was a fact that Mike a (scientific) surfer already knew. The study became rather involved and rather large very quickly. In total Mike devoted some 300 hours to this work and some one hundred visits to the Plum Island shore during 2008. To this day, Mike can't help but observe which way the sand is moving along the beach on any given day.

Mike presented the results of his work in a Power Point presentation to members of the Army Corp of Engineers at Congressman John Tierney’s Office in June of 2008 where it was well received. In the same month he also made a presentation to the Newbury Beach Committee who felt that every resident of Plum Island should view this information. Through the summer of 2008 Mike refined his presentation & gathered more photographic data. In September he presented his study to the Town of Newbury where after he received a standing ovation. Impressed with his work & message, The Massachusetts Audubon Society had Mike make an encore presentation in October. Since then Mike has devoted his efforts to making this information more widely available to the Public through the development of this website and further presentations to interested groups. The Town of Salisbury enlisted his expertise in evaluating their shore line as well and aired his presentation on Salisbury Cable TV during the summer of 2010. Segments of Mike's Presentation, "Unlocking the Mystery of Beach Erosion at Plum Island" can be viewed  on this website. "In a Nutshell “as it is called, zeros in on the key issues facing Plum Island.

Tuesday, 05 March 2013 02:04

Sustainable Solutions

Written by

In our efforts to stabilize a river entrance and occupy a migrating & fragile dune system, we have fought natures processes, with little understanding and respect of them. Consequently we’ve disrupted sand migration & are the cause of the very erosion we are fighting. We now have an understanding of Nature’s processes, that we didn’t have 100 years ago. It’s not an inexpensive or easy problem to solve, but the dynamics can be made to work in our favor. If we finally accept the opportunity to work with nature’s processes, then maybe we can end our 100 year fight against them.

"River Dredging & Beach Nourishment - Unsustainable Solutions"

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

"Sustainable Solutions"

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

 

Tuesday, 05 March 2013 02:01

Super Storm Sandy – A Meteorological Near Miss

Written by

Super Storm Sandy, October 29, 2012

The earth is engaged in a never ending struggle to balance its temperature extremes - that is the extreme cold at the poles with the extreme heat of the tropics. The job of tropical weather systems is to vacuum heat from the tropical oceans & deliver it to the poles. Conversely cold fronts & cold core low pressure systems take the cold from the poles & cast it south over the warm oceans, cooling  the warm sea which concurrently warms the cold air mass. This dance of cold & warm air oftentimes results in intense storms. Some storms are purely tropical, like Hurricanes, while others are purely cold core, such as Nor’easters that tap their heat energy from the warm Gulf Stream. Others however are a combination of the two – a Hybrid storm. These hybrid systems typically occur in the fall when ocean temperatures are the warmest, tropical systems are common, and the northern jet tracks cold core low pressure systems further south where they feed off this tropical heat energy. These intense storms form because of the relative extreme contrast of the two clashing air masses & the immense amount of heat energy infused by a tropical system. With the temperature of the oceans rising, it is logical to conclude that there is more heat energy available & hence a greater clash to be had when the air masses collide.

 Atlantic 2012 HuricaneTrack Summary Weather Underground

2012 Atlantic Hurricane Track Summary – Most Tropical Systems Don’t Impact us.

Envision the Atlantic as an immense bowling alley & the east coast population centers are its pins. Each year the tropics roll a series of systems in our direction. While the majority of tropical disturbances don’t have much punch, and many end up as “gutter balls” curving back out to sea, some do manage to develop into “strikes”, impacting the U.S. east coast, but that isn’t so common. More common are cold core low pressure systems that ride up the east coast, feeding off the Gulf Stream, sometimes “striking” as intense Nor’easters.  As we transition from summer into fall & winter, tropical systems often combine with advancing cold core systems to produce some very intense “Hybrid Storms” – part Hurricane, part Extra Tropical Low. Hybrid storms happen quite often. Virtually every tropical system that is drawn northward transitions or becomes absorbed into a cold core area of low pressure. We just don’t hear much about them as this frequently occurs NE of us, in the North Atlantic. However, sometimes variables align such that this clash happens closer to home. Three noteworthy storms that most adults of today will remember are the Perfect Storm or Halloween Gale of 1991, the Halloween Northeaster of 2011 that dropped a foot of snow and was also accompanied by huge seas, and of course Super Storm Sandy in October of 2012. Interestingly, all three of these systems unleashed their fury during the last week of October. 

The Perfect Storm October 1991 Photo: NOAA

perfectstorm Satellite  Oct 30 1991

The Halloween Northeaster October 30, 2011 Photo: Washington.edu

Halloween 2011 Noreaster Oct 30 Wash Univ

Super Storm Sandy October 29, 2012  Photo: NASA

 Sandy satellite-Oct-29

On the grand scale of things, Plum Island dodged a bullet with Sandy. A meteorological wobble in the storm which spanned 1000 miles of ocean, altered its storm track by 150 miles, sparing New England, while devastating Long Island & New Jersey. Let’s examine how close we came.

As Sandy tracked N/NE off the mid- Atlantic coast, she was blocked by an area of low pressure to her east & high pressure to her N/NW. This funneled the storm into the Northeast U.S. It became a challenge of predicting how far north she’d travel, before she was forced west, after which she would stall.  Had the storm continued north for just 6-12 additional hours before turning west, she would have made land fall on Long Island, instead of southern New Jersey. This 150 mile alteration in storm track would have placed her northern wind-field & storm surge across Massachusetts, where she may have stalled for 3 days as she spun herself down. Imagine 6 storm tide cycles; it would have changed the landscape.

Our Worst Case Scenario Wind & Sea State- a Long Island Landfall for Sandy

Worst-Case-E-LI-Landfall-Oct-28

New Jersey & Long Island’s Devastation would have been ours…

Seaside Heights Sandy Aftermath  Photo: AP IMAGES

Seaside Heights sandy aftermath AP Images

Sandy Forms a New Inlet  Photo: Reuters

 Sandy forms a new Inlet Reuters

Where Would Our New Inlet Form? Photo: Mike Morris

The Next Inlet

 

(Scroll down for Power Point Slides)

Long ago, the Plum Island & Salisbury Beach Barrier Islands formed transgressively in response to a slowly warming planet that prompted a gradual rise in sea level. Wave action plowed glacial deposits landward, shallowing the sea. Once sands were washed above sea level by varying wave energies, winds took over & built dunes. Since the process was gradual, plants were able to take root, building the Islands vertically, as they captured the wind driven sands driven ashore by ocean waves. Overtime the sea continued to rise, storms helped to erode the foreshore & dunes, sometimes even creating new inlets. Waves would eventually top the dunes in low spots, pushing sands to the island’s rear. As the foreshore was encroached upon by the sea, plant growth would retreat & eventually establish itself in these over wash sands. As a result, the island would in effect slowly “transgress” or retreat toward the mainland, migrating over the salt water marsh in the process.

Because all of this happened slowly over thousands of years, the marsh located behind the barriers, had the opportunity to also retreat as waters rose & the islands encroached upon them. Offshore of Salisbury beach for example, it is possible to see the peat & clay of an ancient marsh rising from the sea floor, as the barrier’s sands continue to migrate westward. If you walk the beach following large wave events, you might find parts of this peat broken up & washed ashore there.

Today, due to Human Induced Climate Change, storms are more frequent & intense, and sea level is rising faster than it ever has in the world’s Geologic past. Scientists are uncertain about how fast sea level will rise, & how quickly barrier Islands & their backwater marshes will, or can respond. If barrier island retreat happens too quickly, the marshes may not be able to keep pace with the rising waters & the advancing sand mass.  This will have far reaching ecological impacts, one of which will severely impact local fisheries. For developed Barrier Islands, recent history reveals that the combination of climate induced sea level rise coupled with climate enhanced storm activity, will have devastating results when barrier over wash & new inlet formation occurs. In fact, long before the water gets uncomfortably high in the calm bays & estuaries, or begins to seep up the streets along the backside of Plum Island, climate enhanced storm activity & frequency will begin to dramatically alter the shore. A hotter ocean contains more heat energy & a warmer climate will allow the atmosphere to absorb more moisture. When the meteorological variables align (as they did with Super Storm Sandy & the February 2013 Blizzard) the ingredients will combine to produce incredibly intense storms. Climate change & Sea Level Rise will have far reaching implications for Humanity & our Planet. Implications, we are just beginning to understand. As the climate warms & sea levels rise, we are literally entering uncharted waters.

For more on this topic and its implications read John Englander’s:

High Tide on Main Street: Rising Sea Level and the Coming Coastal Crisis
By John Englander; Foreword by Jean-Michel Cousteau                            
Publisher: The Science Bookshelf; ISBN 978-0615637952

"Climate Change, Sea Level Rise & Barrier Island Retreat"

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

Tuesday, 05 March 2013 01:59

The Barrier Dune System

Written by

The barrier dune system represents a second line of defense for our shore & Barrier Island. Our first line of defense is the Beach Berm – the sandy area between the dunes & the water where you place your towel or chair to spend a day at the beach. But the Beach Berm is really a no man’s land for sand. With nothing to cling to wind moves sand along the beach, into the dunes or even back into the water. The Beach Berm is like your check book. The sand or money that’s there today isn’t the same sand or money that will be there tomorrow, or in a week. With constant withdrawals & deposits, we strive to maintain an average, albeit transient “Daily Balance”. Like unexpected expenses, storms can make large withdrawals from a Beach Berm, but a healthy barrier dune acts like a savings account, keeping the checkbook in balance when necessary. Erosion occurs when withdrawals exceed deposits & the sand reserves of the Barrier Dune have been depleted. 

On developed shores, the Barrier Dune system is at best neglected & most often severely compromised. There the dunes can’t store sand as the dunes themselves are filled with houses. On Plum Island, the Barrier Dune system that we rely on has dwindled to a slim sliver of sand. With climate change & sea level rise a reality, a robust barrier dune system is essential to preventing storm induced wash over & Barrier Island Retreat. We should learn to treat it well.

(To Illustrate Certain Points, Some of the Power Point Slides contain Images from Salisbury Beach & are so noted)

“The Barrier Dune System”

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

 “How to Grow a Sand Dune”

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

Tuesday, 05 March 2013 01:58

Beach Groins

Written by

As waves wash along a beach they naturally move sand along the shore. The direction that sand moves is dependent on the angle at which waves approach the beach. Beach groins are structures, oftentimes made of stone, placed perpendicular to the shore to act as dams, restricting the movement of migrating sand. Watch this short animation to see how waves move sand along a shore…

“Long Shore Drift Animation”

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

Given prevailing wave origins, sand migration along a shore is typically in one direction. While Periodic reversals do take place, they are short lived. The Beach on Plum Island faces just slightly Northeast.  Wave approach is primarily from the E & SE. This drives sand north from roughly the middle of the Wild Life Refuge to the river jetty. In contrast, offshore near the River Mouth, the southern half of the Merrimack River delta bar faces Southeast. With the same angle of wave approach, this simple change in orientation of the delta bar, promotes a southerly sand migration offshore. So, offshore the sand moves south & on the beach it travels north. One can envision a circulation here.  You can view the journey that Plum Island Sand makes below:

“Plum Island Sand Journey”

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version

So how do groins affect sand migration on the shore at Plum Island? When the shore is wide, these groins are covered with sand & have no effect on the shore profile. However, when the shore narrows & the groins become exposed, they gather sand on one side, while promoting erosion on the other. If you own a home on the north side of a groin at Plum Island, you are at risk.

“How a Beach Groin Works”

Viewing Instructions: Click lower right corner to expand viewing size.  Click to advance slides & animations

Custom Flash - Free Version