Sedimentation rates in the ponds are
also quite high (Table 12). The amount
of sediment that originated by resus-
pension of bottom sediments in ponds
ranged from 816 mm for the summer
of 1992, or approximately equivalent
to the thickness of new sediments de-
posited in the ponds during the same
period. During the winter 199293 pe-
riod, sedimentation from resuspension
ranged from 215 mm, or amounts
similar to those of the summer 1993.
A 1994 Pond Sediment
Winter 199394 resuspension rates
-- cumulation (mm/summer):
c
------------------------
could not be calculated because the
5
0-05
1 -10
plate collection devices were not
10-15
cleared in the fall of 1993. Using the
N
5-20
0
sedimentation stations established in
1994, we found that summer resus-
pension sedimentation ranged from 0
7 mm (slightly less than in previous
500 m
years).
Pond sedimentation rates vary in
a. Northwest tile.
space and time across the Flats because
of the interactions of processes and
physical constraints described earlier.
Summer sedimentation rates for moni-
tored ponds across ERF are summa-
rized in Figure 48. During the summer
of 1994, the highest sedimentation rates
(1520 mm) were recorded in the
ponds of Bread Truck, Area C and Area
A (Fig. 48a, b). Sedimentation rates at
intermittent ponds ranged from 1 to
15 mm per summer; however, the rate
0
0-5 mm/summer
at station 1 (Fig. 10) was anomalously
5-10 mm/summer
higher, having 24 mm per summer.
10-15 mm/summer
15-20 mm/summer
500 m
EROSION DYNAMICS
Gully erosion is one of the most vis-
ible mechanisms that is currently modi-
fying and reshaping the Flats. Simi-
N
larly, Eagle River migration also causes
considerable change (Tables 14). Be-
cause of the rapid dynamics associ-
ated with river and gully erosion, the
rates of erosion and recession need to
be quantified and integrated into our
modeling of the physical system. This
quantification is critical because nu-
b. Northeast tile.
merous gullies are experiencing head-
Figure 48. Summary of sediment accumulation in pond locations
ward erosion towards several of the
during summer 1994.
most contaminated ponds on ERF.
36
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