4 minute read
Oranjestad Shoreline
Oranjestad, Aruba
Using an adaptive shoreline management technique to nourish a sand-scarce beach. Approximately 40 kilometers of Aruba’s roughly 80-kilometer-long coast are undeveloped, and sand is scarce. Covering 402 meters of this coastline on a recreational beach that is traversed daily by thousands and resting three kilometers north of a cruise ship terminal, the project site suffered from chronic sand loss and erosion. The sand had eroded to the point where only rock was present. During weather cycles, the sand would naturally accrete. However, this did not happen for about a year where it had in the past naturally occurred. Buildings were on the verge of being threatened, and the beach was unusable. To address conditions and add resiliency to this coastline, geosynthetic containers, manufactured by Solmax, were deployed in various groin layouts. Sand had to be carefully sourced from proximate areas where it accumulated naturally in shoals or localized areas because barging is the only other source of sand. The sand deposited between the control groins, along with the groins themselves, provided protection during larger wave events that previously washed the sand away. After deployment, and with some nourishment, sand remained in place and resilient through large storms.
Article Cover: Aerial view of the Oranjestad Shoreline project. Ongoing monitoring and intermittent GPS monitoring are currently being carried out. (Photo by Little Environments)
Producing Efficiencies
The layout and sizing of the geosynthetic composite containers were based on weather and wave patterns. The site is on the leeward side of the island 99% of the time, and waves there are the result of larger waves that come from the east and wrap around the island. Slight changes in wind direction, from east to eastnortheast, can cause drastically different wave and coastal dynamics. Preliminary groin layouts were installed, and orientations that naturally promoted sand accretion were extended farther while groins that did not perform as well were not extended.
Using Natural Processes
Instead of using dredging and heavy machinery, the use of control points with the innovative composite harnessed the natural forces of the local coastal dynamics to deposit sand using the force of the waves themselves during calm conditions when the water washed up and retracted. The geosynthetic composite containers held the sand at these point control locations. They offset and pushed seaward the shearing force of the water in the littoral current and wave approach so that sand between these controlled point locations remained. The more the project progressed with installation, the more sand accumulated.
Broadening Benefits
Besides a sandy beach where before there was none, the project has yielded numerous environmental and recreational benefits. Hard and soft sea creatures accumulate below the wash line on the geosynthetic containers, and fish congregate there to feed on them. Puffer fish (Tetraodontidae) and snapper (Lutjanidae) are common. Pelicans (Pelecanus) and other seabirds rest on the containers. And fishermen walk atop the containers to reach areas once inaccessible because of hazardous rocks. At the project’s far northwest end is a bunker used in World War II to watch for incoming ships. A bar built over the bunker prevents it from being eroded and undermined.
Promoting Collaboration
Working across borders and across languages is sometimes difficult, especially on a small island with limited access to machinery and other supplies readily available on the mainland. The Dutch-Aruban owners of the project worked with the engineers and environmental consultants at Little Environments, PLLC, in Raleigh, North Carolina, to develop a process for installing the geosynthetic composite containers using their own maintenance and landscaping teams. Minimal heavy machinery was used on the project. The primary machinery used for the installation was a small sand pump installed atop the hull of a salvaged Hobie Cat sailboat.
