Southeastern Section - 62nd Annual Meeting (20-21 March 2013)

Paper No. 5
Presentation Time: 9:35 AM


LARSON, Rebekka A.1, BROOKS, Gregg R.2, DEVINE, Barry3 and FORNI, Morgan1, (1)Marine Science, Eckerd College, 4200 54th Ave S, St. Petersburg, FL 33711, (2)Marine Science, Eckerd College, 4200 54th Avenue South, St. Petersburg, FL 33711, (3)St. John, 00830, US Virgin Islands,

Sediment distribution patterns and rates of sediment accumulation have been documented by an extensive database of >100 sediment cores collected from a variety of USVI coastal environments. This provides a territory-wide baseline of the natural and human influenced impacts to terrigenous sediment accumulation in these environments. A key factor contributing to sedimentation is the natural susceptibility of these islands to excessive erosion and transport of island-derived sediments to coastal environments as a result of: 1) steep island slopes, 2) unstable composition of the rocks (easily weathered), and 3) the hot and humid climate.

The primary objective of this project was to develop a tool, termed the Sediment Susceptibility Index (SSI) that can be easily used to help guide island development and “decision making”. The SSI is a means of comparing the susceptibility of coastal environments to changes in sediment accumulation due to land use changes in the up-gradient watershed. The SSI is defined as the “degree” or “magnitude” of the deviation in sedimentation, called “human impacted”, from “naturally" deposited sediments. The SSI consists of a five tier ranking system (least susceptible/no deviation to most susceptible/maximum deviation) of coastal sediment input/accumulation susceptibility. The tool developed here dominantly measures the rate of input of island-derived sediments to a coastal environment vs the capacity of the marine physical processes (waves, tides, currents) to export that material out of the adjacent coastal environment(s).

The integration of sediment distribution and accumulation rates with other data will help to determine the extent of sedimentation changes due to anthropogenic activities throughout the territory as well as other similar island settings. The SSI can also aid in identifying watersheds with the greatest potential for sedimentation impacts and aid in identifying patterns and trends to target emerging problematic watersheds.