c/EPA
EPA-840-B-21002
April 2021
The Recover}' Potential Screening Tool-
Screening for Land-Based Sources of
Pollution that Stress Coral Reefs
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Acknowledgements
This research was supported in part by an appointment to the U.S. Environmental Protection
Agency (EPA) Research Participation Program administered by the Oak Ridge Institute for
Science and Education (ORISE) through an interagency agreement between the U.S. Department
of Energy (DOE) and the U.S. Environmental Protection Agency. ORISE is managed by ORAU
under DOE contract number DE-SC0014664. All opinions expressed in this paper are the
author's and do not necessarily reflect the policies and views of US EPA, DOE, or
ORAU/ORISE. This report was prepared by Kaitlyn Brucker (ORISE Fellow) with support from
the EPA Healthy Watersheds Program, primarily Emily Cira (EPA), and Andrew Somor
(Cadmus).
The following people provided their time and expertise as technical reviewers for this report:
• Miranda Chien-Hale (EPA)
• Nick Rosenau (EPA)
• Hudson Slay (EPA)
• Bill Fisher (EPA)
• Susan Jackson (EPA)
This report also benefitted greatly from review and comments from: Terri Johnson (EPA),
Katherine Weiler (EPA), Grace Robiou (EPA), Kevin Hollerbach (EPA), Catherine Brady
(EPA), Patrick Keeler (Bureau of Statistics and Plans-Coral Reef Conservation Program),
Whitney Hoot (Bureau of Statistics and Plans-Coral Reef Conservation Program), and Cara Lin
(National Coral Reef Management Fellow).
The findings reported herein are made available for informational purposes only.
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Purpose
The purpose of this document is to advise coral reef practitioners and local governments on using
the Recovery Potential Screening (RPS) Tool to evaluate and compare watersheds for sediment
and nutrient runoff into coral reef ecosystems. This document is not a comprehensive overview
of the tool, but rather an introduction to the tool's specific features that may be relevant for coral
reef protection. This document includes the following sections:
• Background
• Introduction to RPS Tools
• Setting up an RPS Tool
• Interpreting the Results of an RPS Tool
• Applying an RPS Tool to Prioritize Watersheds for Actions to Reduce Sediment and
Nutrient Runoff to Coral Reef Ecosystems
• Indicators Relevant for Sediment and Nutrient Runoff to Downstream Coral Reefs
Resources with in-depth instructions have been created by EPA and its partners and are provided
in the "Additional RPS Tool Resources" secti on at the end of this document. Support for RPS
Tools is provided by EPA's Healthy Watersheds Program (HWP-Team@epa.gov).
Background
Coral reefs are precious marine ecosystems. An estimated 25% of all marine life is dependent on
coral reefs at some point in their lifecycle. Coral reefs also benefit coastal communities by
stimulating tourism and providing shoreline protection. A study completed by the U.S.
Geological Survey (USGS) entitled Rigorously
Valuing the Role of U.S. Coral Reefs in Coastal
Hazard Risk Reduction estimated the value of
shoreline protection provided by coral reefs to
coastal communities to be close to two billion U.S.
dollars annually (Storlazzi et at. 2019).
Unfortunately, coral reefs are at risk because they
are susceptible to many different threats, including
local, land-based pollution. EPA and its partners
work to address many land-based pollution sources
that impact coral reefs, including excess sediments
and nutrients, which can negatively interfere with
the respiration, feeding, growth, recruitment, and
reproduction of corals (Figure 1). Improved
management of land-based sources of pollution can improve the health of coral reefs. This was
further illustrated in a National Academies of Science (NAS) study, A Decision Framework for
Interventions to Increase the Resilience and Persistence of Coral Reefs. This study demonstrated
that the management of land-based pollution sources and sustainable fishing practices are
essential to increasing the resilience of coral reefs to elevated ocean temperatures, which leads to
coral bleaching and higher disease prevalence (NAS, 2019).
The RPS Tool provides a systematic approach for comparing watersheds and can be used by
coral reef practitioners and local governments to prioritize watersheds for management actions to
* v
2* •
r* m
-• *
Figure 1. A photo highlighting an effect of land-
based sources of pollution on corals. Excess
sedimentation leads to smothering of the coral
colony.
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reduce nutrients and sediments in watershed runoff. As described below, customized RPS Tools
have been created and are available, for all US states and territories, including Hawaii, Florida,
Puerto Rico, US Virgin Islands (US VI), Guam, American Samoa, and the Commonwealth of the
Northern Marianas Islands (CNMI). Access to state and territory tools can be found at
https://www.epa.gOv/rps/downloadable-rps-tools-comparing-watersheds#Statewide.
Introduction to MPS Tools
The term "RPS Tool" used throughout the document refers to any number of custom-coded
Excel spreadsheets designed to support watershed comparison and prioritization. Each RPS Tool
is configured for a given state or territory and stores pre-calculated watershed
characteristics/considerations (described as indicators) for that area. RPS Tools can also be
readily updated with user-supplied indicator data. Interactive menus allow users to set up a
screening by choosing relevant watersheds and indicators. Recovery potential scores and ranks
are automatically calculated by the tool based on user settings. Screening results are displayed in
table, graph, and map forms, giving managers options when communicating results to
stakeholders and decision-makers.
Most RPS Tools allow for the comparison of 12-digit Hydrologic Unit (HUC12) sub-watersheds
(see definition here: https://enviroatlas.epa.gOv/enviroatlas/glossarv/glossary.html#huc) from the
National Watershed Boundary Dataset maintained by USGS and the Natural Resources
Conservation Service. Alternative watershed scales, such as state-specific watershed
delineations, are available in some RPS Tools based on information provided by state or territory
water programs.
Detailed instructions for choosing watershed indicators and conducting a screening analysis can
be found within each RPS Tool and on the RPS Training and User Support website found at
https://www.epa.gov/rps/rps-training-and-user-support. The following sections present a broad
overview of highlights and options in RPS Tools and present specific considerations for coral
reef practitioners and local governments.
Setting up an RPS Tool
As shown in Figure 2, RPS Tools use three categories of indicators (Ecological, Stressor, and
Social) to compare watersheds within a state or territory. The three categories contain several
different indicators that can be combined and evaluated to create a Recovery Potential Integrated
(RPI) Index score.
• Ecological indicators measure the current condition of aquatic ecosystems and the
watershed's capacity to maintain or reestablish natural structure, function, and resilience.
Examples of ecological indicators include percent forest in the watershed, percent grassland
in the watershed, and soil stability.
• Stressor indicators measure the presence and amount of human activity in the watershed that
can increase pollutant loading and degrade aquatic ecosystems. Examples of stressor
indicators include population density, percent agriculture in the watershed, and percent urban
cover in the watershed.
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• Social indicators address community, regulatory, economic, and/or behavioral factors that
influence watershed management approaches and planning. Social indicators are not
typically measured from national datasets and, therefore, are often augmented by users with
information from states or territories. For this reason, pre-calculated social indicators may or
may not be present in RPS Tools. Examples of social indicators include percent protected
lands in the watershed, presence or absence of Marine Protected Areas, and presence of
active watershed groups.
Fishing
Demand
% Intact
Riparian
Zone
Drinking
Water
Intakes
Ecological
Index
(High Scores =
Setter Condition)
Stressor
Index
(High Scores =
Greater Stress)
Social
Index
(High Scores =
Favorable Traits)
Recovery Potential Integrated (RPI) Index
Figure 2. Simplified graphic of how the Ecological, Stressor and Social indices are evaluated and combined into the
Recovery Potential Integrated Index (RPI). Indicators within each category are combined to calculate Ecological
Index, Stressor Index, and Social Index scores. In addition, an overall RPI Index Score is calculated by combining
the Ecological Index, Stressor Index, and Social Index. Together, the indicators and index scores are used to
compare watershed characteristics and can be identify priorities for watershed management initiatives to reduce
sediment and nutrient loading to coral reef ecosystems.
A screening run typically uses between 3 and 12 indicators per category. A list of example
indicators that may be useful for sediment and nutrient screenings can be found in the "Indicators
Relevant for Sediment and Nutrient Runoff to Downstream Coral Reefs" section. Including too
many or too few indicators can negatively affect the usability of RPS Tool outputs. Specifically,
the inclusion of too many indicators can confound distinctions between watersheds because of
the way RPS scores are generated. Alternatively, using too few indicators can skew the results by
neglecting relevant information. RPS Tools require users to include at least one indicator per
category to conduct a screening run. Therefore, if a user does not wish to evaluate the watersheds
by one of the categories, the "Neutral Variable" indicator within the category should be selected
before running the screening. Selecting the "Neutral Variable" for a category tells the RPS Tool
to rank all the watersheds equally for that category; therefore, the category will not influence the
overall RPI index score.
Indicator selection is an important decision that should reflect the screening objectives. Each of
the selected indicators should provide a different 'piece of the puzzle' within the three categories.
An RPS Tool may include pairs of indicators calculated from the same dataset, but are inverses
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of one another and grouped into separate categories. For instance, the ecological indicator of soil
stability is the inverse of the stressor indicator soil credibility. Using both indicators in the same
screening does not provide any extra information. Furthermore, they will cancel each other out in
the RPl calculations. Other cases of indicator correlation may be explored as part of indicator
selection. However, since RPS is a screening-level tool, a detailed analysis of indicator
correlation is not commonly completed. By default, indicators are weighted equally during a
screening, but a user may change the weights based on relevance to the screening objectives or
expert insight. Indicators with higher weights will have a greater influence on the calculated
index scores. An example weighting scheme is to assign each indicator a value of 3, 2, or 1,
implying high, medium, or low relevance, respectively.
Interpreting the Results of an MPS Tool
Results from RPS Tools have been applied in various ways, including prioritizing watersheds for
management actions. In general, it can be beneficial first to determine the target profile of
watershed conditions for anticipated management actions (for example, highly degraded
watersheds versus watersheds that are healthy but vulnerable). The Ecological, Stressor, Social,
and RPI Index scores can then be reviewed together to identify watersheds that fit the desired
profile.
Indicators and Index Scores/Ranks
A screening's results are generated in various formats, including tables, charts, and maps,
displaying indicator values, index scores, and rank orders. Each result can provide useful
information for identifying priority watersheds:
• Single indicators provide an opportunity to understand specific watershed-to-watershed
differences. Sometimes a single indicator can be closely related to suitability for a specific
restoration technique or best management practice. For example, watersheds with high scores
for the stressor indicator soil erodibility might be ideal areas to plant vegetation stabilizing
stream banks.
• The Ecological Index, Stressor Index, and Social Index scores combine indicators from each
category into index scores that range from 0 to 1. The meaning of each index is summarized
in Table 1. The Ecological Index, Stressor Index, and Social Index are intended to be
reviewed in consideration of each other to identify watersheds that have preferred traits for
prioritization across the three categories.
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Table 1. Summary of the Ecological Index, Stressor Index, and Social Index scores.
Index Type
Directionality and Meaning
Ecological Index
Score
Higher values = Better condition of natural landscapes supporting
healthy aquatic ecosystems and watershed functions (hydrologic,
geomorphic, and water quality regimes)
Stressor Index Score
Higher values = Greater exposure to factors (agricultural or urban
land cover, nutrient or sediment loads, etc.) that could degrade the
condition of aquatic and downstream marine ecosystems
Social Index Score
Higher values = Positive social characteristics for prioritization
(community involvement, meeting program and policy
requirements, presence of socially valued resources, data
availability, etc.)
• The RPI Index Score combines the three indices into an overall value or score. While there is
value in comparing watersheds by way of an overall score, the RPI score should not be relied
upon as the only screening product. The RPI score can range from 0 to 1, with higher values
corresponding to better ecological and social conditions and lower stressor exposure. In other
words, watersheds in good ecological condition with a positive social context and low
stressors score well. For additional information on how RPI scores are calculated in RPS
Tools, please refer to the RPS Tool's User Manual found on the RPS Training and User
Support website (https://www.epa.gov/rps/rps-training-and-user-support).
When reviewing index scores, it is essential to remember that the results will reflect only those
indicators used in the screening. For example, if a screening only included stressor indicators
related to urban development, the Stressor Index would not reflect any potential degradation
from other sources such as agriculture or mining.
Rank-Ordered Tables
RPS Tools generate tables of results for the screened watersheds that can be sorted by any
indicator value or index score. Rank-ordering organizes the screened watersheds from highest to
lowest score for each of the four indices. Rank orders provide an easy and transparent method to
identify a smaller, targeted subset of watersheds for action by selecting a specific number or
percentage of favorably ranked watersheds.
The selection of priority watersheds through rank-ordering can be a straightforward approach to
using RPS Tool results. However, while results are useful for characterizing significant
differences between high- and low-scoring watersheds, they do not support distinctions among
minimal scoring differences in RPS Tool results. One option for organizing rank-ordered lists in
a more generalized ranking is to group the watersheds by quartiles or percentiles.
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Bubble Plots
RPS Tools produce bubble plots that allow users to visualize the Ecological, Stressor and Social
Index scores of each watershed at the same time (Figure 3). The bubble plot offers a systematic
way to understand how the ecological, stressor and social characteristics of each watershed vary
relative to the rest of the screened watersheds.
The bubble plot displays watersheds as circles with the Stressor Index score plotted on the
horizontal axis and the Ecological Index plotted on the vertical axis. Circle size is determined by
the Social Index score (a larger circle corresponds to a higher Social Index score). By default, the
chart axes are set at the median of Ecological and Stressor Index values for all watersheds
included in the screening. The axes split the bubble plot into four quadrants, which can provide a
system for grouping and prioritizing watersheds:
• The Upper Left
quadrant contains
watersheds with
high Ecological
Index and low
Stressor Index
scores. These
watersheds often
represent the
healthiest
watersheds that
may be good
prospects for
nrf. .• n , Figure 3. Bubble plot produced by an RPS Tool. The scores are divided into four
' ' ° quadrants, which can provide insight to what kinds of management strategies would be
with some suitable for each watershed.
minimally impaired watersheds that are not under severe pressure from stressors and may be
good prospects for restoration. Reefs influenced by these healthier watersheds (less sediment
and nutrient runoff) could benefit from other types of restorative activities outside of the
watershed (e.g., algae/invasive species removal or implementation of an MP A). Because of
the good condition, coastal zones linked to these watersheds might be considered a good
option for coral outplanting.
• The Upper Right quadrant contains watersheds with high Ecological Index and high Stressor
Index scores. These results suggest good ecological conditions, but an elevated risk from
stressors. Watersheds in the upper right quadrant may be good candidates for immediate
management action to reduce sediment and nutrient loading due to their vulnerable status.
Reefs influenced by these watersheds may also be considered highly vulnerable due to the
greater potential for a transition from relatively low to high sources of land-based pollutants
compared to other watersheds in the screening. Prioritizing management activities to
watersheds in this quadrant could mitigate the risk of degraded water quality before
ecological degradation is experienced on the reef.
UPPER LEFT
high eco, low stressor scores
best condition
maybe more responsive to
restoration/protection locally
t
LOWER LEFT:
low eco, low stressor scores,
seldom a top priority
less stressor reduction opportunity
probably not in great condition
UPPER RIGHT:
high eco, high stressor scores.
- still in good condition
- but higher stressor index
- possibly more threatened
Stressor Index
Circle size increases with Socii
LOWER RIGHT:
low eco, high stressor scores.
- good tor efforts reducing stressors
- likelihood of local recovery may be
low
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• The Lower Right quadrant contains watersheds with low Ecological Index and high Stressor
Index scores. These watersheds may contain severely degraded aquatic ecosystems and high
levels of human disturbance to the landscape and watershed functions. Watersheds in the
lower-right quadrant may be good candidates for reducing large sediment and nutrient loads
or other significant stressors. Still extensive time and effort may be needed for complete
ecosystem recovery. Similarly, the reefs influenced by these watersheds are more likely to
have greater exposure to land-based sources of pollution. Depending on stressor
characteristics, watershed management plans may identify projects intended to reduce
significant pollution loads to adjacent reefs but would require more complex management
planning to address the greater number and types of pollutant sources. Furthermore, reefs
influenced by these watersheds may be significantly altered and require more time to recover.
• The Lower Left quadrant contains watersheds with low Ecological Index and low Stressor
Index scores. These watersheds may contain aquatic ecosystems that have been affected by
other factors not considered in the group of stressor indicators selected for the screening and
may be good candidates for more detailed evaluations of the sources of degraded water
quality.
It is important to note that the presence of a watershed in any of the quadrants is always in
relation to the other watersheds included in the screening. If more watersheds are added, or some
subtracted from the screening, the quadrant for a watershed could change. This affects
interpretation of the data. For example, a watershed in the upper left quadrant might be the best
possible candidate for coral outplanting from among the watersheds considered, but it still may
lack the environmental quality to support newly planted corals.
Maps
Maps are a useful method for visualizing a
comparison of watersheds (Figure 4). Like the
two techniques described above, mapping
offers strengths and weaknesses for
interpreting and applying RPS Tool
results. Maps are commonly used to
communicate results to wide audiences, but a
map can only display one indicator or index
score at a time. An RPS Tool includes basic
mapping capabilities that allow users to
develop customized maps of any indicator or
index. Data tables from an RPS Tool can also
be saved and transformed for additional
processing in GIS software.
Maps of screening results can reveal
geographic patterns such as clusters or corridors of high or low index scores. One advantage of
mapped results is the potential recognition of watersheds which, if restored, could link
J
Legend
RPI Score
16.80 - 25.64
25.65 - 33.43
33.44 - 36.62
36.63 - 38.21
38.22 - 48.56
48.57 - 58.99
59.00 - 64.82
{y ^
_
64.83 - 69.17
. m
_
69.18 - 75.07
^^7
_
75.08 - 80.77
Not Analyzed / No Data
Figure 4. A map ofSaipan produced by the CNhfl RPS Tool.
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watersheds across a larger region that are in good condition. Maps can also support
geographically based strategies for targeting priority watersheds.
Applying an MPS Tool to Prioritize Watersheds for Actions to Reduce
Sediment and Nutrient Runoff to Coral Reef Ecosystems.
As noted above, excess sediments and nutrients from land can be detrimental to coral reefs by
interfering with critical biological functions. However, due to the dynamic nature of ocean
environments, some reefs are more influenced by land-based sources of pollution than others.
Studies have shown that wave height, wave direction, and nearshore currents can influence the
persistence of land-based sources of pollution near coral reefs. Nearshore currents may carry
runoff from other watersheds to different reef communities. Additionally, threats such as
overfishing, increasing sea surface temperatures, and invasive species introductions can impact a
coral reef ecosystem's health. All of these variables can obscure connections between watershed
management and coral reef health (Rodgers etal., 2012). RPS Tools do not account for
oceanographic variability or anthropogenic pressures in the marine environment. As such, an
RPS Tool should not be used as the sole means for assessing a watershed for prioritization of
ridge to reef management strategies. Rather, an RPS Tool aids in evaluating and comparing of
watersheds that may produce polluted runoff to an adjacent coral reef ecosystem and should be
used in conjunction with other environmental considerations. Suppose characteristics of
sediment or nutrient runoff have been identified as impactful stressors to coral reefs in a state or
territory. In that case, an RPS tool can help determine which watersheds to prioritize for
management actions.
The listed indicators, found in the following three tables (Tables 2-4), are examples of factors
that may be relevant to managing watershed nutrient and sediment runoff. The tables include the
names of the indicators, their descriptions, explanations of their relevance to coral management,
and the state or territorial RPS Tools that include each of them. The indicators in the first table
are ecological indicators; the second table contains stressor indicators; and the last table is
comprised of indicators of differing categories that are not truly features of the watershed. These
non-watershed features are indicators that are depictive of the adjacent coastal/reef conditions
and can provide important details for decision making. More detailed descriptions, including the
data sources, can be found within each RPS Tool, on the Indicator Info tab of the Excel
spreadsheet.
The indicators provided in the following tables represent a selection of indicators that can be
found in the state and territory RPS Tools. Many other indicators that may be useful, depending
on specific management objectives. If a specific indicator is not available in a state or territory
tool please contact EPA's Healthy Watersheds Program at HWP-Team@epa.gov.
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Indicators Relevant for Sediment ani Nutrient Runoff to Downstream Coral Reefs
Table 2. Ecological indicators within RPS Tools that many be relevant to managing sediment and nutrient runoff from watersheds to coral reef ecosystems.
Ecological Indicators
Indicator Name
Description
Relevance to Corals
RPS Tools
with Indicator
N-Indcx2
Percent of the watershed classified
as natural land cover (not including
barren land). Natural land cover
classes arc captured in the N-indcx2
include forest, wetlands, shrub kind,
grassland, and aquatic beds.
Aquatic ecosystems arc connected to the landscape through surface and
subsurface drainage. Natural land cover throughout a watershed maintains
hvdrologic processes such as infiltration, cvapotranspiration. and groundwater
recharge, and protects aquatic ecosystems from nonpoint sources of pollution,
including urban and agricultural runoff.
Hawaii and
CNMI
Soil Stability,
Mean in
Watershed
Mean soil stability in the watershed.
Soil stability is the inverse of soil
credibility, calculated as the average
of credibility grid values per
subwatcrshcd.
Natural levels of erosion supply sediment in an amount and rate that support
healthy aquatic ecosystems by maintaining natural channel morphology and
bed substrates. Soil stability represents the susceptibility of soil to erosion
from surface runoff. Coarse-textured, sandy soils and soils high in clay have
low credibility and high stability values. Soils with a high silt content arc the
most crodiblc and the least stable. They arc easily detached and produce high
rates of runoff. Continual erosion and excess sediment have been linked to
coral habitat degradation and may exacerbate nutrient, water temperature, or
other stressors.
Hawaii
Watershed
Health Index
Score
The mean Watershed Health index
score for the watershed. The score is
an evaluation of overall watershed
health, derived from the levels of
human disturbances across a set of
land cover classes. Scores were
developed by the Hawaii Institute of
Marine Biology at the University of
Haw aii at Manoa.
H igher values correspond to a greater ability of the land cover types within the
watershed to support higher levels of water quality and healthy ecosystems in
streams and rivers. Streams and rivers with good water quality and healthy
aquatic ecosystems are supportive of healthy coral reefs downstream.
Hawaii
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Table 3. Stressor indicators within RPS Tools that many be relevant to managing sediment and nutrient runoff from watersheds to coral reef ecosystems.
Stressor Indicators
Indicator Name
Description
Relevance to Corals
RPS Tools
with Indicator
Soil Erodibility,
Mean in
Watershed
Mean soil erodibility in the
watershed. Mean soil erodibility
was calculated as the average of
erodibility grid values per
subwalershcd.
Natural levels of erosion supply sediment in an amount and rate that support
healthy aquatic ecosystems by maintaining natural channel morphology and
bed substrates. Soil erodibility represent the susceptibility of soil to erosion
from surface runoff. Coarse-textured, sandy soils and soils high in clay have
low erodibility values. Soils with a high sill content are the most credible and
the least stable. They arc easily detached and produce high rates of runoff.
Continual erosion and excess sediment have been linked to coral habitat
degradation and may exacerbate nutrient, water temperature, or other stressors.
CNMI. Guam.
American
Samoa. Hawaii.
Florida. USVI
% Agriculture
Percent of the watershed classified
as agriculture cover. Agriculture
cover includes "Cultivated Land"
and "Pasturc/Hav" land use lavcrs.
Croplands and pastures have been linked to a wide variety of water quality and
biotic impacts. Common effects seen at moderate to high agriculture land
cover include less diverse and more tolerant macrobcnthic communities,
increased nutrient loading resulting in turbid water, accelerated erosion and
bank dcstabili/ation. suspended sediment particles carrying pesticides,
pathogens, and heavy metals, habitat degradation and reduced biodiversity, and
increases in specific conductivity, nitrogen, and phosphorus concentrations
which can increase macroalgal growth in coastal areas.
CNMI. Guam.
American
Samoa. Hawaii.
Florida. USVI
% Agriculture
on > 10% Slope
in Watershed
Percent of the watershed with
agriculture cover on slopes greater
than or equal to 10 percent.
Agriculture cover classes include
"Cropland" and "Pasture" land use
lavcrs.
Soil erosion is amplified on steep slopes as runoff gains energy and more
readily detaches soil particles while moving downhill. Agricultural areas arc
prone to erosion since they often have reduced vegetative cover relative to
forests and grasslands and contain soils that arc disturbed bv tilling or
livestock. Areas that combine both agricultural land use and steep slopes arc
therefore a concern for high rates of export of sediment and sediment-bound
pollutants such as nutrients and pesticides into nearby waters.
CNMI. Guam.
American
Samoa. Hawaii.
Florida. USVI
% Impervious
Su rface
Percent of the watershed classified
as "Impervious Surface' cover.
Impervious surfaces are defined as
hard surfaces including rooftops,
parking lots, major roads, streets,
sidewalks, driveways, and surfaces
that are impermeable to infiltration
of rainfall into underlying
so i 1 s/groundwater.
Impervious surfaces in a watershed can increase the flashiness of streamflow, CNMI, Guam,
including high rates of stormwater runoff, reduced infiltration, and reduced American
groundwater recharge. This increases the potential for polluted runoff to reach Samoa, Hawaii,
coastal areas. Florida, USVI
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Stressor Indicators
Indicator Name
Description
Relevance to Corals
RPS Tools
with Indicator
% Poorly
Drained Soils in
Watershed
Percent of the watershed with soils
rated as poorly drained. Poorly
drained soils include Groups C and
D in the Hvdrologic Soil Group
classification system applied bv the
US Department of Agriculture
(USDA) Natural Resource
Conservation Service
: (https://www.nrcs.usda.gov/wps/PA
. =stelprdb1262857&ext=pdf).
The drainage characteristics of soils determine the potential for rainfall to pond
and runoff into surface waters. Soils arc classified into four Hvdrologic Soils
Groups based on properties such as depth, texture, and the presence of dense
layers that restrict downward water movement. Soils with poor drainage
(Hvdrologic Soils Groups C and D) have high potential for surface runoff,
which can transport soil particles and pollutants that accumulate on the land
surface into streams, lakes, and coastal waters.
CNMI. Guam.
American
Samoa. Hawaii.
Florida. USVI
NPDES Permit
Count
Number of National Pollutant
Discharge Elimination System
(NPDES) permits issued to facilities
located in the watershed.
Wastewater treatment plants, factories, and other point sources of discharge
into surface waters arc regulated NPDES. The number of NPDES permits
issued in a watershed is an indicator of the presence and complexity of point
source pollutant discharge. NPDES permit counts may be related to the
magnitude of point source pollutant loading, but higher permit counts do not
always correspond to higher pollutant loads. For example, a watershed may
contain a single, large NPDES permitted wastewater treatment facility that
discharges higher pollutant loads than the combined total of several smaller
facilities located in another watershed. Therefore, permit counts should be used
as a starting point for further investigation of the types of discharges within
watersheds.
CNMI. Guam.
American
Samoa. Hawaii.
Florida. USVI
Local /Ru ral
Road Density in
Riparian Zone
Density of local and rural roads in
the riparian zone of the watershed
(defined in each RPS Tool as land
within 100 meters of a stream or
river). Includes unpaved roads or
vehicle trails and minor roads that
may be paved or unpaved. Major
roads such as state/territory
highways or county roads arc not
counted in this indicator.
Roads can be important sources of pollutants to aquatic ecosystems due to the
accumulation and wash off dust, soil particles, plant residue, and vehicle
fluids. Unpaved roads, in particular, can have very high rates of sediment
production and transport. Roads located in the riparian corridor can have
greater influence on aquatic ecosystems compared to upland roads due to their
proximity and increased likelihood for direct runoff into a walcrbody.
CNMI. Guam.
American
Samoa. Hawaii.
Florida. USVI
Landscape
Development
Index Score
The mean Landscape Development
Intensity score in the watershed.
Higher values arc reflective of
increased human disturbances to the
landscape including impervious
Higher values correspond to greater extent of land cover that can degrade coral
reef health.
Hawaii
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Stressor Indicators
Indicator Name Description
Relevance to Corals
RPS Tools
with Indicator
surfaces, agriculture, houses, roads,
and industrial infrastructure.
% Projected Sea
Level Rise
Inundation,
(0,1,2,3,4,5, or 6)
Ft Scenario
Percent of the watershed that is
inundated under various sea level
rise scenarios: zero. one. two. three,
four. five, or six feet of sea level
rise. These data depict the potential
inundation of coastal areas resulting
from current Mean Higher High
Water (MHHW) conditions.
Increases in sea level could result in the inundation of wetlands as well as
developed areas which could impact stormwalcr drainage as well as sediment
and nutrient runoff.
CNMI
Population
Density in
Watershed
Human population density in the
watershed (persons per square
kilometer). Source data were from
the 2010 US Census.
Large human populations reduce natural vegetative cover through conversion
to urban and agriculture lands, while human settlement in riparian corridors
removes the buffer between watcrbodics and upland development.
Additionally, higher populations arc associated with increased wastewater
discharge from sewage treatment plants, septic systems, and industrial sites
and also a greater potential for water withdrawals and hvdromodification
(channelization, dams, levees, etc.)
Hawaii. CNMI.
and Guam
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Table 4, Indicators beyond the watershed that may influence management decisions.
Indicators Beyond the Watershed that May Influence Management Decisions
Indicator Name Category Description
Relevance to Corals
RPS Tools
with Indicator
Presence/Absence
of Marine
Protected Areas
Social
Presence/absence of Marine
Protected Areas (MPAs) in the
watershed (1= presence: 0=
absence).
MPAs provide alleviation of various stressors and arc reflective of
valued resources and potential social motivation to improve or
maintain marine habitats. Pairing an MPA with upstream
watershed management activities could increase the protection
provided to the area.
Hawaii and
CNMI
Predicted Reef
Health Index
Score
Ecological
The mean Predicted Reef Health
Index (RHI) score for coral reef
areas adjacent to a watershed.
Predicted RHI scores arc derived
from statistical modeling of coral
distribution and abundance based
on environmental and fishing
pressure data.
Higher values correspond to greater potential for healthy coral
reefs to be present downstream of the watershed. Predicted Reef
Health Index Score should be evaluated as a single indicator that is
then compared to the Stressor Index score. Watersheds that have
high scores for this single indicator and the high Stressor Index
score arc indicative of healthy reefs at risk from poor water
quality. Prioritizing management activities in these watersheds
could mitigate the risk of degraded water quality before ecological
degradation is experience at the reef.
Hawaii
Surveyed Reef
Health Index
Score
Ecological
The mean Surveyed Reef Health
Index (RHI) score for coral reef
areas adjacent to a watershed.
Surveyed RHI scores are derived
from samples of coral distribution
and abundance.
Higher values correspond to the presence of healthier coral reefs
downstream of the watershed. Surveyed Reef Health Index Score
should be evaluated as a single indicator that is then compared to
the Stressor Index score. Watersheds that have high scores for this
single indicator and the high Stressor Index score are indicative of
healthy reefs at risk from poor water quality. Prioritizing
management activities in these watersheds could mitigate the risk
of degraded water quality before ecological degradation is
experience at the reef.
Hawaii
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Additional MPS Tool Resources
Website
The Environmental Protection Agency provides further information about RPS Tools online:
https://www.epa.eov/rps
https://www.epa.gov/rps/rps-training-and-user-support
YouTube videos
The Environmental Protection Agency has developed a series of instructional videos that can be
found here:
https://www.voutube.com/watch?v=8ZLamP4hYvs&list=PL7F4YD5AdOGJ^ o M:jzOC
Skqnnate&index=l
Contact
HWP-Team@epa.gov
References
Ku'ulei, S. R., Kido, M. H., Jokiel, P. L., Edmonds, T., & Brown, E. K. (2012). Use of integrated
landscape indicators to evaluate the health of linked watersheds and coral reef environments in
the Hawaiian Islands. Environmental Management, 50(1), 21-30.
National Academies of Sciences, Engineering, and Medicine 2019. A Decision Framework for
Interventions to Increase the Persistence and Resilience of Coral Reefs. Washington, DC: The
National Academies Press, https://doi.org/10.17226/2524.
Storlazzi, C.D., Reguero, B.G., Cole, A.D., Lowe, E., Shope, J.B., Gibbs, A.E., Nickel, B.A.,
McCall, R.T., van Dongeren, A.R., Beck, M.W., 2019, Rigorously valuing the role of U.S. coral
reefs in coastal hazard risk reduction: U.S. Geological Survey Open-File Report 2019-1027.
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