Lawson, D.E., and B.E. Brockett (1993) Prelimi-
90% when a silt fence was not used in the test.
nary assessment of sedimentation and erosion in
Because of differences between lab and field use
of this product, several recommendations are
Eagle River Flats, south-central Alaska. USA Cold
made to help ensure the proper functioning of the
Regions Research and Engineering Laboratory,
geotextile when used in Eagle River Flats. These
CRREL Report 9323.
recommendations include monitoring the quanti-
The physical processes of sedimentation and
ty of material with diameters larger than 0.1 mm
erosion within the tidal mudflats and salt marshes
passing through the silt fence, careful and fre-
of Eagle River Flats (ERF), an area used as an artil-
quent visual inspection of the silt fence to detect
lery impact range by the U.S. Army since 1945,
any signs of strength loss or damage, having
must be understood to evaluate potential treat-
replacement geotextile available and properly
ments of a high duck mortality resulting from
stored at the site, backflushing the silt fence with
ingestion of white phosphorus (WP) particles. The
water or rubbing it with a squeegee regularly to
WP originates from smoke-producing devices
help ensure proper flow rates across it, and not
detonated here. A preliminary assessment of ero-
allowing the depth of soil retained on the
sion and sedimentation during May to Septem-
upstream side of the fence to exceed one-half of
ber 1992 indicates that the physical system is
its height.
complex and the intensity of these processes spa-
tially variable. Deposition from suspension sedi-
mentation generally varied with morphology
Lawson, D.E., S.R. Bigl, J.H. Bodette, and P.B.
Weyrick (1995) Initial analyses of Eagle River
and elevation, increasing inland from levees on
Flats hydrology and sedimentology, Fort Rich-
the Eagle River (1 to 2 mm) across vegetated (3 to
ardson, Alaska. USA Cold Regions Research and
6 mm) and unvegetated (5 to 12 mm) mudflats,
Engineering Laboratory, CRREL Report 955.
and into ponds (10 to 19 mm) and salt marshes
The physical environment of Eagle River Flats
(10 mm). Resedimentation rates in ponds ranged
(ERF), a subarctic tidal flat and salt marsh, is pro-
from 8 to 16 mm. Recession rates of eroding gully
gressively changing because of the interactions of
headwalls were highly variable, ranging from
multiple physical processes, including a high
negligible to over 3.9 m. White phosphorus parti-
tidal range, two primary sediment sources, cold
cles may be in suspended transport through gul-
climate, and location within an active earthquake
lies during ebb. Further studies are necessary to
zone. In addition, ERF has been used by the U.S.
better define annual sedimentation and erosion
Army as an artillery range, where high explosives
rates, with improved sampling techniques used
or smoke-producing shells have been detonated,
at an expanded number of sites. Basic data on tidal
causing cratering and disrupting drainage. The
inundation, sediment influx and efflux, and WP
physical environment of ERF needs to be under-
particle transport are required to develop appropri-
stood to help remediate a problem of unusually
ate treatment methods.
high mortality rates in migrating waterfowl. This
high mortality of ducks is attributable to inges-
Lawson, D.E., L.E. Hunter, and S.R. Bigl (1996)
tion of elemental white phosphorus (P4) particles
Physical processes and natural attenuation alter-
(from smoke-producing devices), which are now
natives for white phosphorus contamination,
distributed within near-surface sediments of the
Eagle River Flats, Fort Richardson, Alaska. USA
Cold Regions Research and Engineering Labora-
ponds and marshes. The complexity of this dynam-
tory, CRREL Report 9613.
ic environment makes it extremely difficult to
This report describes the results of investiga-
predict what physical effects remedial measures
tions into the role of tidal flat physical systems in
ly, what short- and long-term effects the physical
the natural attenuation of white phosphorus
system will have on the effectiveness and success
of proposed remedies. Understanding both the
Fort Richardson, Alaska. Waterfowl feeding in
system's response and the effects of remedial
ponds and marshes here ingest the WP and die.
technologies is critical to deciding what measures
These investigations found that natural attenua-
are used. This report presents the initial analysis
tion and in-situ degradation of the WP could
of the physical processes of erosion, sedimenta-
result from certain physical phenomena operat-
tion, and sediment transport and the factors con-
ing within the ERF ecosystem. Specifically, the
trolling their activity within a portion of ERF.
on-going erosion and headward recession in the
gullies will drain large areas of contaminated
83
to contents
to index
Previous Page
