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.