DUNES RECONSTRUCTION
FLAMENCO BEACH, CULEBRA, PUERTO RICO
PROJECT STATUS | IN PROGRESS
PROJECT BACKGROUND
The Flamenco Beach Recovery Project is an interdisciplinary, replicable, and collaborative effort. It started as a reaction of the devastation inflicted by hurricane Irma and Maria in 2017 and wants to integrate the community in the process of rehabilitation and preservation of its coastal forest, water, and dune systems, allowing them to implement and learn the value of conservation practices including water reuse and green infrastructure. This section focuses on the dunes reconstruction component of the threefold strategy used in this project for the recovery of the beach.
AN IMPERMANENT LANDSCAPE
Dunes are shock absorbers that protect the coastal environment and back beach, accumulating and storing sand in normal conditions, while releasing it back to the ocean during storms. They act as dikes against flooding and as a reservoir of sand to replenish the beach. Dunes develop and grow with the help of plants that hold and trap the sand coming towards the direction of maximum wind-blown sand source.
A RELENTLESS PERSISTENCE
Constantly changing, the beach shoreline and dunes profile provide very unstable growing conditions for the dune vegetation, but many plants are well adapted and even resistant, especially the herbaceous perennials, crawling vines and a variety of grass species that are able to grow in the front and tail of the dune facing the ocean’s wind and salt spray.
THE SHAPE OF EROSION
Vegetation also promotes the accumulation of sand from wind-blown sources around their stems, and over time this causes dune growth. Plants growing close to the ocean reduce the impact of wind velocity and trap the sand, keeping much of it in the immediate vicinity of the beach.
DUNES BEFORE AND AFTER IRMA AND MARIA
The tan color indicates the large sand dune area, which was covered by a very lush dune vegetation plant community with narrow openings in correspondence of the pedestrian access to the beach. In 2004, the vegetation covered almost completely, both the frontal dune and the back dune zone, the latter being amore protected area leeward of the front dune.
CARRYING CAPACITY
Most beach users at Flamenco Beach want to sit in the shade of palms and other trees, to enjoy the view and ocean breeze while they are at the very top of the front dune. This habit has increased after the hurricanes, because trespassing is easier without plants in place. In the process, people damage the already exposed plant roots and eroded embankments; they scatter litter and leave their impact, day after day. We need to devise a system that prevents access or transit in the most sensitive dune areas before we even attempt to repair the damage, while keeping Flamenco open to the public.
DO WE HAVE TIME TO WAIT?
The question is, with climate change affecting the intensity of future storms and the rise of ocean levels, and with the continuous heavy impact on the dunes of the beachgoers, which accelerate plant loss and sand erosion, do we have time to wait for the ocean waves, wind, and plants to slowly rebuild the eroded dunes at their pace? In other words, should natural processes be the only means of repair when facing worsening impacts of climate change?
CONTROLLING ACCESS
We suggest closing off three new access points created by people or by storms and flooding that did not exist before. All the other points of access should be kept open but regulated with signage, by dune walkovers, and by rope railings to limit the impact of foot traffic on the dune vegetation. Access walkways will be made of wood and act as a bridge around or over the dune. Access points not heavily used, can receive quite narrow and less visually intrusive wood boardwalks or structures for access.
STITCHING THE DUNES IN TIME
We need a careful surgery of all the open wounds left in the dune habitat before it is too late. We cannot restore all at once or recreate something that is constantly changing (the dune system) and which was never fixed in historical time or form.We can, however, envision a framework where individual interventions will create the means to accelerate the progressive healing of the eroded scarp of the front dunes, in whatever form it will want to manifest over time. Are they needles-like temporary insertions that have a use, and that can take abuse?
WORKING WITH THE WIND
Dunes are intimately connected with the instability of the weather, with the turbulence of the air and wind. They cannot be bound, retained, but can be affected and modified in their growth and form, if we engage and fabricate devices that interact with the phenomena of the wind. Walls set in the bed of a stream slow down the current and cause the silt carried by the water to be deposited in distinct layers, making islands or mounds whose position we anticipate, but whose random shape is not always predictable.
FENCES FOR SAND TO TRESPASS
Sand fences are porous, temporary filters that help rebuild the dune much faster. Rather than barriers, they are sieve instruments that, like plant stems, affect and channel wind turbulence and movement. Wind is not blocked in its passage, but its velocity is reduced enough that the sand carried by it drops into, through and behind the fences because of the 50% porosity of their wood slats. Since they are typically made of light, widely spaced wood slats, sand fences can be constructed and installed easily with the participation of volunteers and local community groups.
EROSION AND DEPOSITION
The back dunes at Flamenco Beach have also lost their sand and organic matter, and much of their sand has shifted on the path or camping ground. We have identified a few areas where we can rake the sand back into the back-dune zone, after proper organic amendment. The new back dunes should not be higher than four feet and never steeper than a normal angle of repose. Since they are typically made of light, widely spaced wood slats, sand fences can be constructed and installed easily with the participation of volunteers and local community groups.
WEIRS FOR A FLUID LANDSCAPE
We will not attempt to reconstruct and reproduce the back dunes in a prescribed, immobilized form, stripping their dynamism into a mere abstraction. They should always be free of movement, if they are alive. Conceptually, we are thinking to help their process of self-organization with “ribbons” of vegetation, to partially hold the mounds of sand on one side like a weir or a small check dam would do for turbulent water flowing downstream.
UMBRELLAS FOR SHADE
To prevent people from picnicking and sitting on exposed roots of palms and sea grapes, we are suggesting that ACDEC provide beach umbrellas for rental, as it is commonly done in non-tropical managed beaches across the world. Beach umbrellas will provide the necessary shade taking people away from the dunes zone, closer to the ocean, and thereby speeding up the recovery process. Wood platforms will also be offered on or nearby the crest of the dune in the most popular areas, which may be for rent to provide income. Rope fencing incorporated in the design of the decking will limit foot traffic to the deck areas, only so that compaction and erosion will be minimized.
AFTERWARDS
The dune rehabilitation is a critical component of the threefold strategy for the Flamenco Beach Recovery project. Click on the text for more information on the Coastal Reforestation component and the Water Infrastructure recovery component.
All Photographs © Rossana Vaccarino Except Where Noted.
Printed On: June 26 2019
Printed At: Doubledey, San Juan, Puerto Rico
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