This report summarizes the current
results of this study, synthesizing previ-
ous work of 1992 and 1993 with the 1994
investigations, and addresses elements
of Objective 1.
STUDY SITES
AND METHODS
Transects
We established our transects to include
representative morphological units, with
11 transects set out in May 1992 (Lawson
and Brockett 1993), 1 in June 1993, and
11 in 1994 (Fig. 7). We surveyed the
transects using an electronic theodolite
to determine ground surface elevations
relative to local benchmarks and the
UTM grid. Grab samples of surface sedi-
ment (to 5-cm depth) were taken at each
survey point along the transects for ana-
lyzing the grain size distribution using
standard sieving and hydrometer tech-
niques. These data are necessary for us
to delineate surfacial textural trends and
to evaluate the relative importance of
the tidal and riverine sediment sources
Figure 6. Drainage pattern analysis of 1993 aerial photograph of C
to sedimentation and landform devel-
and D areas.
opment.
Sedimentation and erosion
STUDY OBJECTIVES
Sedimentation rates in ponds and marshes are
The objectives of this multi-year investigation
difficult to measure accurately because only a
are to:
slight disturbance of the water column will resus-
1. Conduct quantitative analyses of ERF's
pend the fine-grained bottom sediments. If these
physical system dynamics, particularly hydrologi-
sediments are caught in sediment traps, sedimen-
cal, sedimentological and hydraulic processes con-
tation will be over-sampled and the resulting rates
trolling erosion, transport, deposition and burial
high. We, therefore, used several methods to mea-
of WP-bearing sediments. We will develop a con-
sure primary sedimentation rates and related sur-
ceptual framework for the ERF physical ecosys-
face erosion and secondary rates of resedimen-
tem and the fate and transport of WP particles,
tation resulting from resuspension of pond bottom
including the potential for off-site migration.
materials. Rates of sedimentation and surface ero-
2. Evaluate the short- and long-term response
sion at mudflat, levee and tidal gully sites were
and sensitivity of the physical processes and ter-
measured using other techniques.
rain to modifications caused by proposed reme-
We used "sedimentation stakes" to measure
dial technologies, particularly temporary or per-
erosion and deposition at transect points where
manent pond drainage, dredging, capping,
the surface was wet or standing water was present
geotextiles or others as proposed.
(Fig. 8). These stakes consist of a rod and a square,
rigid plate (about 7 cm2) that slides freely on the
3. Assess the effects of the physical system on
the effectiveness and stability of proposed reme-
rod as used by Ovenshine et al. (1976a,b) in
dial measures for WP contamination and develop
Turnagain Arm, Alaska. Erosion depth is defined
strategies for restoring areas of dredging, artifi-
by the increase in distance between the top of the
cial drainage, or other proposed measures.
rod and the top of the plate, as measured periodi-
11
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