Section 319
NONPOINT SOURCE PROGRAM SUCCESS STGRY
Restoring Native Vegetation Reduces Sediment Entering Coastal Waters
A/ + K H I r\ Dry environmental conditions combined with a long history of human
vV3t6rDOQy irnprOVGQ |ancj use nave resulted in severe erosion on Kaho'olawe. Much of the
island has been reduced to barren hardpan, and sediment-laden runoff affects nearshore water quality
and threatens the coral reef ecosystem. Efforts to minimize erosion and restore native vegetation in
two watersheds on Kaho'olawe (Hakioawa and Kaulana) have reduced the amount of sediment entering
the stream/gulch systems and coastal waters and have improved the quality of coastal waters, coral
reef ecosystems and native wildlife habitat.
Problem
The island of Kaho'olawe, the smallest of the eight
main Hawaiian Islands, is approximately 7 miles
southwest of Maui. Kaho'olawe lies within the rain
shadow of the volcanic summit of Maui.
The island has a unique history. Evidence sug-
gests that Hawaiians arrived as early as 1000 A.D.
Kaho'olawe served as a navigational center for
voyaging, an agricultural center, the site of an adze
quarry, and a site for religious and cultural ceremo-
nies. More recently, Kaho'olawe was used as a penal
colony, a ranch (1858-1941), and a bombing range
by the U.S. Navy (1938-1990). The island was also
home to as many as 50,000 goats during a 200-year
period (1793-1993). Throughout the ranching period,
uncontrolled cattle and sheep grazing caused a
substantial loss of soil through accelerated erosion.
An estimated 1.9 million tons of soil peryear is
eroded from Kaho'olawe (Figure 1). This erosion
results in extremely high ocean turbidity following
rainfall events, affecting coral health and reproduc-
tion (although this seems to be improving as a
result of long-term revegetation efforts). In 1990 liti-
gation ended the U.S. Navy's use of the island as a
bombing range and resulted in transfer of the island
to the Kaho'olawe Island Reserve Commission
(KIRC). A cleanup project conducted from 1993 to
2004 set the stage for restoration.
Figure 1. A lack of vegetation
leads to excessive erosion
on Kaho'olawe, which in turn
causes sediment loading into
adjacent marine waters.
Figure 2. Pili grass hay bales
planted with native shrubs create
areas of accretion for highly
erodible topsoil.
Project Highlights
The Hawaii Department of Health, Polluted Runoff
Control Program (PRCP), has provided Clean Water
Act (CWA) section 319 funding to KIRC to initiate
erosion control, reestablish native plant communi-
ties, and improve water quality affected by exces-
sive sedimentation. KIRC is managing the island and
its resources until the island can be transferred to
a sovereign Native Hawaiian
entity. The CWA section 319
funds have been matched by
more than 80,000 labor hours
contributed by volunteers
that helped implement best
management practices (BMPs)
and plant native vegetation.
Native Pili grass hay bales
(Figure 2) and native seed have
been purchased from the U.S.
Department of Agriculture's
Plant Materials Center on the island of Moloka'i,
while other native plants have been acquired from
private nurseries on Maui.
Because the island's average annual rainfall ranges
between 10 and 25 inches (due to its location in
the rain shadow of Maui), irrigating newly planted
vegetation is critical. Project partners use water
from a 1-acre roof catchment system that collects
and stores about 450,000 gallons of precipitation
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Figure 3. Volunteers plant native shrubs and grasses for Hakioawa's revegetation.
annually. Specific activities undertaken by the project
include developing erosion control BMPs, removing
and controlling alien animal and plant species, and
refining revegetation techniques (Figure 3).
Partners developed a watershed-based plan as a
companion document to KIRC's Strategic Plan. It
focuses on activities in the Kaulana and Hakioawa
watersheds. The U.S. Geological Survey (USGS) has
established various monitoring efforts, including:
(1) installing stream gauge stations on Kaulana and
Hakioawa streams to determine discharge, as well
as suspended sediment loading; (2) establishing
soil erosion pin transects to determine erosion
rates, plant survival, plant cover and plant growth;
and (3) monitoring water quality in the nearshore
area (primarily for turbidity). The monitoring portion
of the project will enable the partners to evaluate
restoration techniques and determine the water
quality benefits associated with the restoration.
Results
More than 2,000 volunteers have assisted with the
restoration efforts. While on the island, the volun-
teers also benefit from exposure to historical and
cultural information. Project partners and volunteers
have planted approximately 60,000 plants cover-
ing more than 60 acres as part of the revegetation
effort. Cover measurements of planted WalTi,
a native shrub, have increased 50 percent in one
year. Plant survival rates have increased from 10 to
80 percent when irrigated with water from the rain
catchment for three months following planting.
Although USGS is still collecting baseline data for the
stream gauges and turbidity monitors, it has already
documented several interesting results. Soil erosion
pin transects installed and monitored by USGS are
used to document sediment erosion and accretion
in areas restored with vegetation, as well as those
that have not yet been restored.
USGS recorded five sets of measure-
ments between January 2007 and
May 2009. In the Hakioawa water-
shed, measurements associated with
areas planted with native vegetation
indicate an average soil accretion of
1.12 millimeters (mm), whereas those
associated with areas not planted
indicate an average soil erosion of
5.68 mm. In the Kaulana watershed,
measurements associated with areas planted with
native vegetation indicate an average soil erosion of
0.21 mm, whereas those associated with areas not
planted indicate an average soil erosion of 4.50 mm.
Although the data represent conditions over a
relatively short time frame and might oversimplify
the complex and dynamic processes of erosion and
accretion on Kaho'olawe, it appears that restoring
native vegetation is reducing the amount of sediment
moving over the island, into to the stream gulches
and eventually to the ocean. It should be noted that
these data have been collected very early in the
restoration process and further monitoring data (ero-
sion pin transect data along with stream gauge and
sediment sampling and coastal water monitoring) will
help to better define the reduction in sediment load-
ing and improvements in water quality and habitat.
Partners and Funding
The KIRC, the Hawaii Department of Health, USGS
(Pacific Islands Water Science Center in Honolulu,
Hawaii, and Pacific Science Center in Santa Cruz,
California), the U.S. Department of Agriculture's
Plant Materials Center (Moloka'i), and the efforts
of more than 2,000 volunteers have contributed to
restoring the Hakioawa and Kaulana watersheds
on Kaho'olawe. Since 2004 the Hawaii Department
of Health's PRCP has provided nearly $1.9 million
in CWA section 319 funding; these funds were
supplemented by nearly $1.9 million in matching
funds from volunteer restoration activities. It should
also be noted that KIRC has supported two restora-
tion program staff positions as part of this effort.
Collectively, these funds have allowed KIRC to make
considerable progress in its effort to begin restor-
ing the two targeted watersheds by implementing
innovative methods to minimize erosion and reduce
sediment loads moving from the land into the waters
on and around the island.
I
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-09-001FF
October 2009
For additional information contact:
Lyman L. Abbott, Natural Resources Specialist
Kaho'olawe Island Reserve Commission
808-243-5884 • labbott@kirc.hawaii.gov
Hudson Slay
U.S. Environmental Protection Agency
Pacific Islands Contact Office
808-541-2717 • slay.hudson@epa.gov
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