STUDY PERFORMANCE REPORT
State: Michigan
Project No.:
Study No.: 230702
Title: Effects of sediment traps on Michigan
river channels
Period Covered:
F-80-R-13
October 1, 2011 to September 30, 2012
Study Objectives: The objective of this study is to quantify the effect of sediment removal efforts on
the channel morphology of select Michigan streams. Specifically, we will identify the rate and
spatial extent of change in riverbed elevation and substrate conditions. We will relate these data
to hydrologic, gradient, and valley characteristics of each stream. We will assess suitability of
different river types for sediment traps, and provide recommendations for spacing traps along
rivers to better achieve desired results.
Summary: The data from this study show that excavation of sediment traps generally had only small
effects on mean channel depth and substrate in the streams studied, with changes occurring both
upstream and downstream of the trap. The lateral position of the channels examined remained
constant, indicating little side cutting had occurred. Changes in channel area remain variable and
appear as likely to occur at transects proximal to the sediment traps as at transects located further
upstream or downstream. These results suggest that sediment trap maintenance has not achieved
the desired goals of increased downcutting and exposure of coarse substrates downstream of the
sediment traps studied.
Findings: Jobs 2, 3, and 4 were scheduled for 2011-12, and progress is reported below.
Job 2. Title: Survey bed elevations and substrate conditions.–We re-surveyed bed elevations and
recorded substrate composition from visual observations and pebble counts upstream and
downstream of sediment traps on the Au Sable, Baldwin, East Branch Au Sable, and Little
Manistee rivers as well as Silver Lead and Twomile creeks. All data were error-checked and
incorporated into a Microsoft Access database with data from previous surveys. While adding the
data for the 2012 surveys to the database, we discovered and corrected a coding error for data
from previous surveys. While the coding error did not change the results reported in previous
progress reports, it did cause minor changes (<0.2 ft) to some of the mean channel depth values
reported for 2006, 2007, 2008, and 2009 in tables 1 and 2.
Job 3. Title: Analyze data.−Data collected during earlier reporting periods show little difference in
bed elevations and substrate upstream and downstream of a trap that was recently abandoned in
the Sturgeon River. Although the trap was maintained from 1984 to 2005, mean depth upstream
and downstream of the trap was very similar during the latest survey completed in 2010
(Table 1). Contrary to expectation, both visual observation and pebble count data indicate
coarser substrate upstream of the trap compared to downstream (Table 1, Figure 1). However,
median particle size was again fine at both locations (D50 <0.15 mm), indicating the trap did not
achieve the objective of exposing coarse substrate.
Data collected from other sediment traps show similar results which suggest that trap
maintenance has not achieved the desired goals of increased downcutting and exposure of coarse
1
F-80-R-13, Study 230702
substrates downstream of the trap. For example, data from 2012 continued to show variable
changes in depth and substrate in stream reaches where sediment traps were constructed when
compared to data collected in previous years (tables 2 and 3). Trap excavation created a headcut
upstream of sediment traps in the Au Sable, East Branch Au Sable, and Baldwin rivers as well as
Silver Lead and Twomile creeks. The extent of the headcutting varied by location and ranged
from 0.1 ft in the East Branch Au Sable River and Twomile Creek to 0.7 ft in the Baldwin River.
Channel depth downstream of the sediment trap increased by 0.3–0.5 ft in the Au Sable and East
Branch Au Sable rivers and Silver Lead Creek (Table 2). No change in depth was observed
below the sediment trap in Twomile Creek or the Baldwin River. Depth below the sediment trap
in the Boardman River and both above and below the sediment trap in the Little Manistee River
decreased, indicating aggradation of the channel at these locations. Changes in channel area were
also variable and are as likely to occur at transects that are close to the sediment trap as at
transects located further upstream or downstream. The lateral position of the channel remained
the same throughout all study reaches.
Visual observation data indicated that although sand substrate decreased by 15% downstream of
the trap in the Au Sable River, there was only a 1% increase in gravel substrate. This observation
suggests that observers may be classifying sand and silt/detritus differently from year-to-year
(Table 3). Even though sand substrate decreased downstream of the traps in the East Branch Au
Sable River and Silver Lead Creek, an accompanying decrease upstream of the traps in these
rivers indicates a drop in fine substrate throughout each reach due to headcutting or some other
larger-scale factor other than the sediment trap itself (the observed decrease in sand substrate was
paired with an increase in gravel substrate both upstream and downstream of the trap at the same
locations). Likewise, the increase in sand substrate and accompanying decrease in gravel
substrate above and below the sediment trap in the Little Manistee River indicates changes in
substrate composition occurring at a spatial scale broader than the reach we studied. Minor
differences (≤12%) in sand and coarser substrate composition occurred upstream and
downstream of the sediment traps in the remaining study rivers (Table 3). Pebble count data,
which are less affected by observer bias than visual observations, show that fine substrates
(<2 mm) have decreased downstream of sediment traps in the Au Sable, Baldwin, and East
Branch Au Sable rivers as well as Silver Lead Creek. However, the downstream decreases were
accompanied by upstream decreases of equal or greater magnitude. Pebble count data showed an
increase in the amount of fine substrates downstream of the sediment trap in the Boardman
River, nearly equal increases in fine substrates both upstream and downstream of the trap in the
Manistee River, and no change in substrate composition in Twomile Creek (Figure 1).
Job 4. Title: Write annual performance reports.−This progress report was prepared.
Prepared by: Todd C. Wills
Date: September 30, 2012
2
F-80-R-13, Study 230702
Table 1.–Summary of mean channel depth and visually classified substrate in the Sturgeon River.
Substrate categories (and dimensions in mm) were silt (0.004–0.063), sand (0.064–2), gravel (3–64),
small cobble (65–128), large cobble (129–256) and other (clay, boulder, or wood). U = upstream, d =
downstream of sediment trap. Positive values for net change in depth indicate an increase in channel
depth (deeper), negative values indicate a decrease in channel depth (shallower). Positive values for
net change indicate an increase in percent substrate; negative values indicate a decrease in percent
substrate.
Year
2008
2009
2010
Net
change
a
b
Mean
Location depth (ft)
u
d
u
d
u
d
3.1
3.2
3.1
3.2
3.0
3.3
u
d
-0.1
0.1
Substrate composition (%)
Small Large
Sand Gravel cobble cobble
Na
Silt or
detritus
100
143
100
144
101
142
20
20
13
17
29
28
41
56
63
75
23
58
12
2
14
1
24
0
9
0
0
0
9
0
9
8
-18
2
12
-2
0
0
Total number of depth measurements collected.
Total number of substrate observations.
3
Other
Nb
0
0
0
0
0
0
18
23
10
8
16
13
92
131
92
132
93
130
0
0
-2
-10
F-80-R-13, Study 230702
Table 2.–Summary of change in mean channel depth following sediment trap excavation for
seven study reaches over a ten-year period. Post-excavation data are in bold. Pre-excavation data
were not collected in the Boardman or Little Manistee rivers. U = upstream, d = downstream of
sediment trap. Positive values for net change in depth indicate an increase in channel depth (deeper),
negative values indicate a decrease in channel depth (shallower).
River
Au Sable
Baldwin
Boardman b
E Br Au Sable
Little Manistee c
Silver Lead Cr
Twomile Cr
a
b
c
Location
02
03
04
Mean channel depth (ft)
05 06 07 08 09
12
Na
Net
change (ft)
u
d
u
d
u
d
u
d
u
d
u
d
u
d
1.9
2.0
–
–
–
–
1.8
2.1
3.4
3.7
–
–
–
–
2.0
2.1
–
–
2.6
2.2
1.9
2.1
3.3
3.7
1.6
1.4
–
–
1.9
2.1
–
–
2.6
2.1
1.9
2.0
–
–
1.7
1.5
2.4
2.3
–
–
–
–
–
–
–
–
3.3
3.6
2.0
1.6
2.6
2.5
2.3
2.4
5.3
4.9
–
–
1.9
2.4
3.5
3.5
2.2
1.8
2.6
2.3
584
1,179
400
653
266
594
370
777
554
1,176
487
1056
392
942
0.4
0.5
0.7
0.0
0.0
-0.1
0.1
0.3
-0.1
-0.3
0.6
0.3
0.2
0.0
–
–
4.6
4.9
–
–
–
–
–
–
1.9
1.7
2.7
2.5
–
–
5.3
5.0
–
–
–
–
3.5
3.4
–
–
–
–
2.2
2.1
–
–
–
–
–
–
–
–
–
–
–
–
2.2
2.2
5.2
4.7
2.8
1.9
1.9
2.1
3.3
3.4
2.1
1.9
2.7
2.5
Total number of depth measurements collected.
Trap maintenance discontinued after 2005. Net change reflects 2003–2004 time period.
Trap maintenance discontinued after 2008. Net change reflects 2002–2009 time period.
4
F-80-R-13, Study 230702
Table 3.–Summary of net change in visually classified substrate data following sediment trap
excavation for seven study river reaches. Pre-excavation data were not collected in the Boardman
or Little Manistee rivers. Substrate categories (and dimensions in mm) were silt (0.004–0.063),
sand (0.064–2), gravel (3–64), small cobble (65–128), large cobble (129–256) and other (clay,
boulder, or wood). U = upstream, d = downstream of sediment trap. Positive values for net
change indicate an increase in percent substrate; negative values indicate a decrease in percent
substrate.
River
(Time period)
Silt or
Location detritus
Net change (%)
Small
Gravel cobble
Sand
Large
cobble
Other
Na
Au Sable
(2002–12)
u
d
4
17
2
-15
0
1
0
0
0
0
-4
-3
535
1,094
Baldwin
(2006–12)
u
d
3
7
-4
0
0
0
1
0
0
0
0
-7
364
599
Boardman b
(2003–04)
u
d
-1
-3
3
6
-8
-5
-5
-5
0
0
10
8
161
569
E Br Au Sable
(2002–12)
u
d
-3
7
-16
-19
24
12
0
0
0
0
5
0
334
707
Little Manistee c
(2002–09)
u
d
0
-9
7
17
-6
-6
0
-1
0
0
0
0
418
926
Silver Lead Cr
(2003–12)
u
d
-5
0
-31
-34
35
37
0
0
1
0
0
-3
441
963
Twomile Cr
(2004–12)
u
d
0
18
12
-5
0
0
0
0
0
0
-12
-14
296
864
a
Total number of substrate observations.
Trap maintenance discontinued after 2005.
c
Trap maintenance discontinued after 2008.
b
5
F-80-R-13, Study 230702
Au Sable River
Baldwin River
100%
Percent finer than
Percent finer than
100%
80%
60%
40%
20%
0%
0.01
0.1
1
10
100
1000
80%
60%
40%
20%
0%
0.01
10000
0.1
1
Particle size (mm)
10000
US 10 yrs post-dig (2012)
US 1 yr pre-dig (2006)
US 6 yrs post-dig (2012)
DS 10 yrs post dig (2012)
DS 1 yr pre-dig (2006)
DS 6 yrs post-dig (2012)
East Branch Au Sable River
100%
Percent finer than
Percent finer than
1000
DS 2 yrs post-dig (2004)
100%
80%
60%
40%
20%
0%
0.01
0.1
1
10
100
1000
80%
60%
40%
20%
0%
0.01
10000
0.1
1
Particle size (mm)
100
1000
US 2 yrs post-dig (2004)
US 7 yrs post-dig (2009)
US 2 yrs post-dig (2004)
US 10 yrs post-dig (2012)
DS 2 yrs post-dig (2004)
DS 7 yrs post-dig (2009)
DS 2 yrs post-dig (2004)
DS 10 yrs post-dig (2012)
Percent finer than
100%
80%
60%
40%
20%
0.1
1
10
100
1000
10000
80%
60%
40%
20%
0%
0.01
Particle size (mm)
0.1
1
10
100
1000
DS 4 yrs post-dig (2005)
US 1 yr post-abandon (2009)
DS 1 yr post-abandon (2009)
US 1 yr pre-dig (2004)
US 8 yrs post-dig (2012)
US 4 yrs post-abandon (2012)
DS 4 yrs post-abandon (2012)
DS 1 yr pre-dig (2004)
DS 8 yrs post-dig (2012)
Sturgeon River
Twomile Creek
Percent finer than
100.00%
80.00%
60.00%
40.00%
20.00%
100%
80%
60%
40%
20%
0%
0.01
0.1
1
10
10000
Particle size (mm)
US 4 yrs post-dig (2005)
0.00%
0.01
10000
Silver Lead Creek
100%
0%
0.01
10
Particle size (mm)
Little Manistee River
Percent finer than
100
US 2 yrs post-dig (2004)
Boardman River
Percent finer than
10
Particle size (mm)
100
1000
10000
0.1
1
10
100
1000
10000
Particle size (mm)
Particle size (mm)
US 3 yrs post-abandon (2008)
US 5 yrs post-abandon (2010)
US 1 yr pre-dig (2004)
US 8 yrs post-dig (2012)
DS 3 yrs post-abandon (2008)
DS 5 yrs post-abandon (2010)
DS 1 yr pre-dig (2004)
DS 8 yrs post-dig (2012)
Figure 1.–Cumulative frequency of substrate particle size from pebble counts in eight study
rivers. Substrate particle size categories (and dimensions in mm) were organic and clay (0–0.04mm),
silt (0.05–0.062mm), sand (0.063–2mm), very fine gravel (2–4mm), fine gravel (5–8mm), medium
gravel (9–16mm), coarse gravel (17–32mm), very coarse gravel (33–64mm), small cobble (65–
128mm), large cobble (129–256mm), small boulder (257–512mm), and medium boulder (>512mm).
US = upstream, DS = downstream.
6