The average annual rate of suspended-sediment discharge of the Stony Brook at Princeton, N.J. (44.5 square miles) is about 8,800 tons, or 200 tons per square mile. Annual yields within the basin, which is in the Piedmont Lowlands section of the Piedmont physiographic province in west-central New Jersey, range from 25 to 400 tons per square mile. Storm runoff that transports suspended materials in excess of a ton carries 90 percent of the total suspended-sediment discharge from the basin. Observations of particlesize distributions indicate that the suspended material carried during storms is 55 percent silt, 40 percent clay, and 5 percent sand.
A trend analysis of sediment records collected at Princeton between 1956 and 1970 indicated an increase in suspended-sediment discharge per unit of water discharge during 1956-61. From early 1962 to late 1967, sediment trends were difficult to interpret owing to complicating factors, such as reservoir construction, urbanization, and extreme drought. After 1967, yields decreased.
Variations in sediment yields during the study are attributed to the integrated influence of several factors. A 2.9 percent decrease in croplands and an increase of 5.1 percent in idle and urban land use probably produced a net increase in sediment yields. Construction of seven sediment-retention reservoirs under Public Law 566 resulted in temporary increases in sediment yields. However, based on a trap-efficiency investigation at 1 site, the combined effect of operation of these 7 reservoirs is estimated to result in a 20 percent reduction in sediment discharge from the basin. Other factors that influence the noted decrease include reduction in yields during 5 years of drought, 1962-66, and reduced construction and development during the latter part of the study period resulting from a general economic slowdown.
Additional publication details
USGS Numbered Series
Effects of land use and retention practices on sediment yields in the Stony Brook basin, New Jersey