Crootof A.B.

ESTIMATING THE HUMAN IMPACT ON SUSPENDED SEDIMENT LOADS IN MOUNTAIN STREAMS OF EASTERN PUERTO RICO

Abstract: 
Worldwide, suspended sediment flux entering the oceans each year is increasing due to human activities. Land development in Puerto Rico is causing the island’s mean annual suspended sediment flux to increase. These high suspended sediment yields are unfavorable for human recreation, water treatment, as well as habitat protection. This study attempts to determine if land development in eastern Puerto Rico is significantly impacting suspended sediment (SS) levels. In eastern Puerto Rico lies the Luquillo Experimental Forest (LEF), which has been protected from land development since the 1940s. With 75 percent of the Island’s virgin forests, seven streams (Quebrada 1, Quebrada 2, Quebrada 3, Rio Mameyes Puente Roto, Quebrada Sonadora, Quebrada Guaba, and Rio Icacos) were chosen to represent “natural” suspended sediment conditions. Examining the relationships between drainage area, discharge, suspended sediment concentrations, slope and suspended sediment loads, these seven streams were compared to one stream outside of the national forest, Rio Mameyes Rt. 3, whose watershed is partially used for agriculture and urban purposes. Results indicate that humans are not significantly impacting suspended sediment levels in the Rio Mameyes Rt. 3. Because land development in the Rio Mameyes Rt. 3 watershed is relatively small, less than 20 percent, it is feasible that the agriculture and urban development are not drastically affecting SS levels or the sampling period did not capture the full range of variability. A principal component analysis of drainage area, suspended sediment load, discharge, slope and temperature of the eight streams shows that only one factor, which contains all components, can be extracted.
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