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An Update of Coastal Erosion in Puerto Rico - page 5 / 10





5 / 10

Terrigenous sediments with a high magnetite content (90 to 98% insoluble material) were found along the beach. Heavy flooding and a river crest of more than 5 m flushed sediment from behind the dam on the Río Arecibo and carried it to the coastline. Field observations seven months after the hurricane showed the the amount of magnetite was reduced, possibly indicating return to stable conditions after the hurricane effects.

Punta Salinas

The 1977 to 1981 photographs showed a continuing retreat of the east shoreline at Punta Salinas of almost two meters per year. This is almost the same as the 1950 to 1977 rate. In 1981, the entire east shore was protected with rock riprap (Figure 7). The 1977-1987 photographs show that the conversion from beach to a rock shoreline has stopped the erosion. The change from 1987 to 1999 has been accretion north of the riprap, but a beginning of erosion south of the riprap (Figure 8).

Figure 7. Boulder riprap on the east side of Punta Salinas.

Figure 8. Shoreline changes at Punta Salinas.

The addition of riprap has cut off the source of sand to the Levittown shoreline of Bahia de Boca Vieja. This area eroded appreciably between 1950 and 1971, but was stable from 1971 to 1977. The jetties in the

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