Bio-engineered solution for coastal erosion protection, pt.3

New photos from our project in New Seabury:

Woods Hole Group coastal engineer Peter Markunas reports:

Our bioengineered design for erosion control at Bayswater Seaside was accepted by the Town and Massachusetts DEP as an appropriate soft solution design, and thus permittable for the site for erosion protection in accordance with 310 CMR 10.30.

High energy wave impacts were a complicating factor at the site that we had to consider in our design.  Most soft solutions have been found effective in low impact sites, but the nature of our site demanded that we improve upon them in order to withstand wave and debris forces that would occur at the site.

The key design features include sand-filled lifts of filter fabric and coir matting, and upper level coir fiber rolls to absorb potential wave run-up.

The sand filled lifts are constructed into the bank, approximately 15’-17’ deep, and approximately 2’ in height.  Several layers of the lifts are built on top of one another, set back to develop a 1.5 to 1 slope.  This provides over 50 kips/lf of vertical down force on each impact lift, assuring stabilized anchoring of the lifts.

The filter fabric chosen is capable of withstanding the anticipated stress forces.

The lifts are further protected with 16-gauge pvc bonded wire mesh to assist in debris tear resistance.

Finally, the lower levels of the lifts are further stabilized and protected by two rows of 12” diameter marine grade preserved piles, staggered at 2’ on-center intervals.

 

The design has been accepted by the Town and DEP as an appropriate soft solution design, thus permittable for the site for erosion protection in accordance with 310 CMR 10.30.

The design was developed from over two decades of closely monitored projects involving Woods Hole Group and its staff engineers, coastal geologists and scientist, particularly from projects on the Lower Cape and Nantucket.

Complicating the design is the high energy wave impact nature of the site.  Most soft solutions have been found effective in low impact sites. However, this site, due to its high impact required careful and thoughtful design considerations to improve on already successful soft measures, to withstand wave and debris forces that would occur at the site.

The key design features include sand-filled lifts of filter fabric and coir matting, and upper level coir fiber rolls to absorb potential wave run-up.

The sand filled lifts are constructed into the bank, approximately 15’-17’ deep, and approximately 2’ in height.  Constructing several layers of the lifts on top of one another, set back to develop a 1-1/2H to 1V slope, provides over 50 kips/lf of vertical down force on each impact lift, assuring stabilized anchoring of the lifts.

The filter fabric chosen is capable of withstanding the anticipated stress forces.

The lifts are then further protected with 16 ga pvc bonded wire mesh to assist in debris tear resistance.

Finally, the lower levels of the lifts are further stabilized and protected by a two staggered columns of 12” diameter marine grade preserved piles, at 2’ OC on each column.

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2 Responses to Bio-engineered solution for coastal erosion protection, pt.3

  1. Pingback: Bio-engineered solution for coastal erosion protection, pt.4 | 2Fathom

  2. Pingback: Bio-engineered solution for coastal erosion protection, pt.5 | 2Fathom

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