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Title: Land-based sources of threat to coral reefs in the U.S. Virgin Islands
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Permanent Link: http://ufdc.ufl.edu/UF00095889/00001
 Material Information
Title: Land-based sources of threat to coral reefs in the U.S. Virgin Islands
Alternate Title: Coral reefs in the U.S. Virgin Islands
Physical Description: 12 p. : col. ill., col. maps ; 19 x 28 cm.
Language: English
Creator: World Resource Institute (Org.)
United States -- National Oceanic and Atmospheric Administration
Donor: unknown ( endowment ) ( endowment )
Publisher: World Resources Institute
National Oceanographic and Atmospheric Administration
Place of Publication: Washington D. C.
Washington D. C.
Publication Date: 2006
Copyright Date: 2006
 Subjects
Subject: Coral reef conservation -- Virgin Islands of the United States   ( lcsh )
Coral reef ecology -- Virgin Islands of the United States   ( lcsh )
Corals -- Ecology -- Virgin Islands of the United States   ( lcsh )
Virgin Islands of the United States   ( lcsh )
Genre: bibliography   ( marcgt )
federal government publication   ( marcgt )
non-fiction   ( marcgt )
Spatial Coverage: United States Virgin Islands
 Notes
General Note: Cover title.
General Note: February 2006.
Statement of Responsibility: The Ocean Conservancy
 Record Information
Bibliographic ID: UF00095889
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70080572

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Table of Contents
    Cover
        Cover
    Main
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    Back Cover
        Back Cover
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Land-based Sources of Threat to Coral Reefs in the U.S. Virgin Islands


Project Goal
With support from the U.S. National Oceanic and Atmospheric Administration (NOAA), The "Reefs at Risk" project of the World
Resources Institute (WRI) teamed with NOAA's "Summit to Sea" project to develop and implement analysis of land-based threats to
coral reefs in the U.S. Virgin Islands (USVI) and Puerto Rico. The goal of the collaboration is to support improved management of
coastal ecosystems by developing and making available extensive information on watershed-based threats to these ecosystems,
including identification of watersheds which are highly erosive and those watersheds contributing elevated levels of sediment and
pollution to coastal waters. Data assembled or developed under this collaboration, including analysis results, are published on the
CoastalData CDfor the U.S. Caribbean'. The data CD also serves as a GIS data sampler for both the USVI and Puerto Rico,
allowing users to do their own analysis of land-based sources of threat. This atlas provides a summary of some of the spatial indicators
developed under the project.

Collaboration
The project was implemented by the World Resources Institute and the U.S. National Oceanic and Atmospheric Administration, in
collaboration with many local institutions and other partners. Collaborating institutions were vital sources of information, provided
guidance on the analytical approach, and offered critical review of analysis results. Groups which contributed data or provided
guidance on the project include:

University of the Virgin Islands / Caribbean Data Center (UVI / CDC)
USVI Department of Planning and Natural Resources (DPNR)
Puerto Rico Department of Natural and Environmental Resources (DNER)
U.S. Department of Agriculture
U.S. National Park Service
U.S. National Fish and Wildlife Service
U.S. Geological Survey
The Nature Conservancy
Island Resources Foundation
The Ocean Conservancy
International Coral Reef Action Network (ICRAN)

1 World Resources Institute (WRI) and U.S. National Oceanic and Atmospheric Administration (NOAA), Coastal Data CDfor the U.S. Caribbean,
(Washington, DC: WRI / NOAA, 2005)







Analysis Approach


Alteration of the natural landscape for development, road construction, or
agriculture can have adverse impacts on coral reefs through increased
delivery of sediment and pollution to coastal waters. The threat associated
with land clearing is higher in areas of steep relief, intense precipitation,
and where soils are erosive in nature. This threat is often evaluated
through application of the Revised Universal Soil Loss Equation (RUSLE)
developed by the U.S. Department of Agriculture (USDA). RUSLE is
useful for examining erosion in many agricultural areas, but is less well
suited to the very steep and rutted environments of the U.S. Virgin Islands
where road construction accounts for most erosion.

This study uses several spatial and statistical techniques to characterize
watersheds across the USVI with regard to relative erosion rates and the
threat of land-based sources of sediment and pollutant delivery to coastal
waters. A simplified version of RUSLE (using slope, land-cover,
precipitation, and soil characteristics) is applied, as well as indicators of
road density and erosivity by watershed. Watersheds are an essential unit
for analysis, since they link land areas with their point of discharge to the
sea. The atlas presents a comparison of estimated watershed-based threat
to coral reefs from both land cover change and road development.


Note on watershed boundaries:
In the USVI, official watershed boundaries have been derived and are available from
the USVI Department of Planning and Natural Resources (DPNR) and the University
of the Virgin Islands Conservation Data Center (UVI-CDC). These "official"
watersheds reflect large areas discharging to a single bay, and are relevant for coastal
planning and land management. Most maps in this atlas use these watersheds for
reference. The "Reefs at Risk" project, however, has an interest in hydrologic
modeling of "basins" where land areas are associated with a single point of discharge
to the sea. In order to estimate sediment delivery to coastal waters, we also present
these smaller hydrologic units, called "basins" within this atlas.


Hydrology


Hydrology in the U.S. Virgin Islands

Vulnerability

Relative Vulnerability of Land to Erosion
Mean Vulnerability of Land to Erosion (by watershed)
Mean Vulnerability of Land to Erosion (by basin)

Roads and Erosion

Vulnerability of Roads to Erosion

Estimated Relative Erosion from Roads
(mean for watershed)

Erosion and Sediment Delivery

Relative Erosion Potential (given current land cover)

Relative Erosion Potential (mean for watershed)

Relative Erosion Potential (mean for basin)

Relative Sediment Delivery (sum for basin) and Estimated
Plume


page


Maps






Hydrology in the US Virgin Islands


This map presents two approaches to watershed
mapping. The USVI has mapped "official" watersheds
reflecting large areas discharging to a single bay.
These 53 "watersheds" are relevant for coastal
planning and land management.
SThe "Reefs at Risk" project has an interest in
{ hydrologic modeling of "basins" where land areas
721- are associated with a single point of discharge
to the sea. Over 400 basins with a minimum area
of 6 ha. are presented.



St. Thomas and St. John

River Guts (Sttjriver_guts.shp)
S Watersheds (Sttj_wsuwi.shp)
Basins (derived) (Sttj_basins.shp)






Source:
Watershed boundaries provided by the USVI
Department of Planning and Natural Resources (DPNR)
and the University of the Virgin Islands (UVI/CDC).
SBasins were derived by WRI and NOAA, 2005,
i I under the Reefs at Risk Project.


5 0 5 Kilometers
St. Croix






Relative Vulnerability of Land to Erosion


Physical factors, such as the slope of the land,
the texture of the soil, and the precipitation regime
Influence erosion in an area. We have developed
S.,. a simple indicator of the erosivity of the land
. ~-~-- .:. ... i. based on slope, precipitation, and the K-ffactor
of the soil (erodibility of the given soil type.) This
. indicator does not consider the current land cover
S '' or land use. Rather, it provides an overall
"! '- indicator of erosion-prone areas, and hence,
S- areas where development / land conversion /
road construction should be avoided.


St. Thomas and St. John I Watersheds
Vulnerability to Erosion
M Low





M High


SSource:
"..Relative Vulnerability to Erosion" was developed by
V ."WRI and NOAA, 2005, under the Reefs at Risk Project.
S... Watershed boundaries provided by the USVI
.Department of Planning and Natural Resources
Sand the University of the Virgin Islands (UVI/CDC).


5 0 5 Kilometers
St. Croix






Mean Vulnerability of Land to Erosion (by watershed)


St. Thomas and St. John


Physical factors, such as the slope of the land,
the texture of the soil, and the precipitation regime
influence erosion in an area. We have developed
a simple indicator of the erosivity of the land
based on slope, precipitation, and the K-ffactor
of the soil (erodibility of the given soil type.)
This indicator has been summarized for major
watersheds in the USVI.


Mean Vulnerability by watershed
SLow
-I

High




Source:
"Relative Vulnerability to Erosion" was developed by
WRI and NOAA, 2005, under the Reefs at Risk Project.
Watershed boundaries provided by the USVI
Department of Planning and Natural Resources
and the University of the Virgin Islands (UVI/CDC).


5 0 5 Kilometers






Mean Vulnerability of Land to Erosion (by basin)






SPhysical factors, such as the slope of the land,
Sthe texture of the soil, and the precipitation regime
influence erosion in an area. We have developed

Based on slope, precipitation, and the K-ffactor
S' o of the soil (erodibility of the given soil type.)
This indicator has been summarized for basins
in the USVI.


St. Thomas and St. John


Mean Vulnerability by basin
I Low


High






Source:
"Relative Vulnerability to Erosion" was developed by
SWRI and NOAA, 2005, under the Reefs at Risk Project.
S-Basin boundaries derived from a hydrologic
model by WRI and NOAA, 2005.

5 0 5 Kilometers
St. Croix







Vulnerability of Roads to Erosion


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St. Thomas and St. John


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St. Croi


Roads are a major source of erosion, particularly
in steep areas on tropical islands. Roads are
the largest source of erosion within the USVI.
Erosion is generally most severe during road
construction, but can also result in longer-term
erosion due to exposed shoulders and abrupt
changes in slope adjacent to the road.
We developed an indicator of the relative
vulnerability of roads to erosion based upon
slope, precipitation, and the K-ffactor of the soil
(erodibility of the given soil type.)



= Watersheds
Roads by Vulnerability
Low




I High





Source:
"Vulnerability of Roads to Erosion" was developed
by WRI and NOAA, 2005, under the Reefs at Risk Project.
Watershed boundaries provided by the USVI
Department of Planning and Natural Resources (DPNR)
and the University of the Virgin Islands (UVI/CDC).



5 0 5 Kilometers
m






Estimated Erosion from Roads (mean for watershed)


Roads are a major source of erosion, particularly
in steep areas on tropical islands. We have
developed an indicator of the relative
vulnerability of roads to erosion based upon
slope, precipitation, and the K-ffactor of the soil
(erodibility of the given soil type.) This indicator
has been summarized by watershed. This is an
area weighted indicator, so will be high in areas
of high road density and steep terrain.




St. Thomas and St. John
Mean Road-based Vulnerability by watershed
Low

I
High






Source:
"Vulnerability of Roads to Erosion" was developed
by WRI and NOAA, 2005, under the Reefs at Risk Project.
Watershed boundaries provided by the USVI
Department of Planning and Natural Resources (DPNR)
and the University of the Virgin Islands (UVI/CDC).
SK-


5 0 5 Kilometers
St. Croix






Relative Erosion Potential (given current land cover)


y. -i
5..4


* I -- ..-


I,


St. Thomas and St. John


Agriculture and other land use activities far inland
can have an adverse impact on coral reefs through
the increased delivery of sediment and pollution to
coastal waters. We have developed a simple indicator
of relative erosion rates from the land, given current
land cover. The analysis uses a simplified version of
the Revised Universal Soil Loss Equation (RUSLE)
(USDA, 1989). It incorporates land cover type, slope,
the soil erodibility factor (k-factor), and precipitation
for the peak rainfall month in order to estimate
relative erosion rates for each 30m resolution
grid cell.

Watersheds
Relative Erosion Potential (REP)
Low


High


Source:
"Relative Erosion Potential" (REP) was developed by
WRI and NOAA, 2005, under the Reefs at Risk Project.
Watershed boundaries provided by the USVI
Department of Planning and Natural Resources (DPNR)
and the University of the Virgin Islands (UVI/CDC).



5 0 5 Kilometers
m






Relative Erosion Potential (by watershed)



We have developed a simple indicator of relative
erosion rates from the land, given current land
cover. The analysis uses a simplified version
of the Revised Universal Soil Loss Equation
(USDA, 1989). This incorporates land cover type,
slope, a soil erodibility factor (k-factor), and
precipitation for the peak rainfall month
S in order to estimate relative erosion rates for
all land areas within a watershed. The mean
relative erosion potential (REP) for the watershed
is presented.

St. Thomas and St. John


Mean Relative Erosion (REP) by watershed
Low


High




Source:
"Relative Erosion Potential" (REP) was developed by
WRI and NOAA, 2005, under the Reefs at Risk Project.
Watershed boundaries provided by the USVI
Department of Planning and Natural Resources (DPNR)
and the University of the Virgin Islands (UVI/CDC).


5 0 5 Kilometers
St. Croix






Relative Erosion Potential (by basin)


C7


St. Thomas and St. John


St. Croix


We have developed a simple indicator of relative
erosion rates from the land, given current land
cover. The analysis uses a simplified version
of the Revised Universal Soil Loss Equation
(USDA, 1989). This incorporates land cover type,
slope, a soil erodibility factor (k-factor), and
precipitation for the peak rainfall month
in order to estimate relative erosion rates for
all land areas within a watershed. The mean
relative erosion potential (REP) for the
basin is presented.


Mean Relative Erosion (REP) by watershed
| Low


High






Source:
"Relative Erosion Potential" (REP) was developed by
WRI and NOAA, 2005, under the Reefs at Risk Project.
Basins were derived from elevation data by
WRI and NOAA, 2005.


5 0 5 Kilometers






Relative Sediment Delivery (by basin) and Estimated Plume


Relative sediment delivery by basin is estimated
based on the total relative erosion potential (REP)
within the basin, adjusted by watershed size.
This approach uses a simplified version of
S/- .. the Revised Universal Soil Loss Equation
I -(USDA, 1989). This incorporates land cover type,
slope, a soil erodibility factor (k-factor), and
Precipitation in order to estimate relative erosion
'. rates for all land areas within a watershed. (It
does not specifically examine erosion due to roads.)
Relative sediment plumes were evaluated
based on relative sediment delivery at the gut
outflow and distance from the outflow.
St. Thomas and St. John
Relative Sediment Delivery by basin
_Low

SHigh


Estimated Relative Sediment Plume

Low
Medium
.. High


Source:
"Relative Sediment Delivery" was developed by
SWRI and NOAA, 2005, under the Reefs at Risk Project.
SBasins were derived from elevation data by
WRI and NOAA, 2005.

5 0 5 Kilometers
St. Croix




















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