Evaluating the Effects of Sediment Retention in the Carraízo Reservoir on Coastal Erosion in Loíza, Puerto Rico

Abstract

This study evaluates the effects of sediment retention in the Carraízo Reservoir and coastal erosion in Loíza, Puerto Rico. Since its construction in 1953, the reservoir has accumulated an approximated 11.74 million cubic meters (Mm³) of sediment, with Trap Efficiency (TE) values exceeding 89%, suggesting minimal sediment transport downstream. Historical shoreline data show that Loíza experienced an average retreat rate of -2.55 meters per year (m/yr) between 1951 and 1977, coinciding with the reservoir’s early years of operation. To evaluate potential shoreline recovery, a theoretical scenario based on the Elwha River dam removal, which reversed erosion with the delivery of 13.3 Mm³ of sediment was applied. Results indicate that, if Carraízo’s sediment were fully delivered to the coast, Loíza could experience shoreline accretion of up to 17.6 m/yr. These findings suggest a correlation between sediment retention and coastal erosion in Loíza, Puerto Rico.