ENVIRONMENTAL - International Erosion Control Association

Maho Bay Watershed Road Erosion Reduction Project, St. John, USVI
Mean sediment Standard Deviation
Period production (kg cm-1) (kg cm-1)
Pre-treatment 240.5054282 91.27083025
Post-treatment 74.17300726 53.11734379
350
300
Sediment production (kg cm -1)
250
200
150
100
50
0
Pre-treatment
Post-treatment
Figure 2. Middle portions of Maho-Road
prior to the installation of the five cemented
swales. The deep rill meandering across the
road travelway formed as a result of the
approximately 5–10 cm of rainfall associated
with Hurricane Georges in September 1998.
pre-treatment rate of 240 kg cm -1 (300
Mg ha -1 yr -1 ) (Figure 4). These mean
rates were found to be statistically different
based on a standard T-Test comparison.
Differences in precipitation
patterns could not account for the disparity
as the post-treatment period was
characterized by rainfall intensities that
slightly exceeded those during the pretreatment
phase. Data analyses proved
that the establishment of five cemented
swales and a paved ditch induced a significant
reduction in the rate of sediment
production from Maho-Road.
The decrease in sediment production
Figure 3. Middle portions of Maho-Road
after the installation of the cemented swales
and the inside ditch.
rates is attributed to three factors: (a) a
decrease in the erosive energy of runoff
flowing over the road surface; (b) the
additional protective cover provided
by the cemented swales and the paved
ditch; and (c) an increase in the resistance
to erosion caused by coarsening
of the road material due to the reduced
need to re-grade the road surface. The
results of this study should stimulate
the use of this erosion control method
elsewhere in St. John and other islands
of the Eastern Caribbean wherever the
application of more costly methods are
not economically feasible or desirable.
Figure 4. Mean sediment production rates
in kg per centimeter of rainfall for the pretreatment
and post-treatment periods. Error
bars refer to one standard deviation.
The results of this study have encouraged
us at Island Resources Foundation
to recommend the application of a very
similar method for an erosion control
strategy for the Fish Bay watershed
being funded by the Gulf of Mexico
Foundation and the National Fish and
Wildlife Foundation.
Dr. Ramos-Scharrón is a Hydro-Geomorphologist
with a PhD from Colorado
State University. He is currently a program
associate with the Island Resources
Foundation and a post-doctoral researcher
with the University of Puerto Rico.
References
[1]
MacDonald, L.H., Anderson, D.M., Dietrich, W.E., 1997. “Paradise threatened: Land use and erosion on St. John, U.S. Virgin Islands.” Environmental
Management, 21(6): 851-863.
[2]
MacDonald, L.H., Sampson, R.W., Anderson, D.M. 2001. “Runoff and road erosion at the plot and road segment scales, St. John, US Virgin
Islands.” Earth Surface Processes and Landforms, 26: 251-272.
[3]
Ramos-Scharrón, C.E., MacDonald, L.H. 2005. “Measurement and prediction of sediment production from unpaved roads, St. John, U.S.
Virgin Islands.” Earth Surface Processes and Landforms, 30(10): 1283-1304.
[4]
Ramos-Scharrón, C.E., MacDonald, L.H. in press. “Measurement and prediction of erosion rates from natural and anthropogenic sources of
sediment in St. John, U.S. Virgin Islands.” Catena Special Issue-Soil water erosion on rural areas.
[5]
Ramos-Scharrón, C.E., 2004. “Measuring and predicting erosion and sediment yields on St. John, U.S Virgin Islands.” Ph.D. Dissertation,
Department of Geosciences, Colorado State University, Fort Collins, Colorado.
[6]
Anderson, D.M., MacDonald, L.H. 1998. “Modelling road surface sediment production using a vector geographic information system.”
Earth Surface Processes and Landforms, 23: 95-107.
[7]
Ramos-Scharrón, C.E., MacDonald, L.H. 2007. “Development and application of a GIS-based sediment budget model.” Journal of Environmental
Management, 84: 157-172.
[8]
Ramos-Scharrón, C.E., MacDonald, L.H. 2007. “Runoff and suspended sediment yields from an unpaved road segment, St. John, U.S. Virgin
Islands.” Hydrological Processes, 21(1): 35-50.
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