NONPOINT SOURCE SUCCESS STORY
Replacing Culverts on Osborn Creek Improves Stream Channel Stability
Waterbody Improved
Undersized and perched road culverts caused flow
alterations in Osborn Creek, which led to stream channel
erosion and sedimentation that degraded aquatic habitat. Restoration efforts, which
included replacing culverts with bridges, decreased sedimentation and improved habitat in
the creek. As a result of these efforts, migratory fish can move through Osborn Creek and
access upstream tributaries.
Problem
Osborn Creek (Assessment Unit ID number
040601010803-02) is a tributary to the North Branch
White River in west-central Michigan's Oceana
County.
An undersized and perched culvert at Pierce Road on
Osborn Creek caused upstream sediment deposition
and downstream channel erosion, and prevented
upstream migration of native fishes, including brook
trout and sculpin, as well as stocked salmonids. The
plunge pool immediately downstream of the culvert
eroded and destabilized the adjacent stream bank,
causing sediment deposition in a riffle immediately
downstream (Figure 1). Significant quantities of soil
also eroded from the Pierce Road roadbed onto the
Osborn Creek floodplain near the stream crossing.
Project Highlights
Since 2011, nine culverts on Osborn Creek were
replaced using a variety of funding sources. On Pierce
Road, a 6-foot culvert was replaced with a 20-foot by
7-foot timber bridge (see Figure 1). Prior to replace-
ment, the plunge pool immediately downstream of
the culvert was 40 feet wide and 5.6 feet deep, com-
pared to a normal channel width of 26 feet and depth
of 2.7 feet at a nearby riffle. After replacement, sandy
floodplain benches had formed in this reach, reduc-
ing channel dimensions to 32 feet wide and 1.8 feet
deep (Figure 2, next page).The road approaches to
the stream crossing were paved as well, reducing soil
erosion from the Pierce Road roadbed.
Figure 1. Osborn Creek, looking upstream
toward Pierce Road, before (top) and after
(bottom) an undersized culvert was replaced
with a bridge. Before being replaced, the
perched culvert had prevented upstream fish
migration. Erosion on either side of the culvert
had contributed excess sediment to the creek.
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Figure 2. Osborn Creek, looking downstream away from
Pierce Road, before (left) and after (right) the culvert was
replaced. Downstream sedimentation has declined, allowing
the stream to become deeper and narrower.
Results
Channel stability in the plunge pool downstream
of the culvert on Pierce Road was assessed using
the U.S. Environmental Protection Agency's stream
function metric of bank height ratio (BHR), which is a
measure of channel down-cutting, floodplain access
and bank erosion potential. Before the culvert was
replaced, the BHR of the deep plunge pool was 3.0
("not functioning"); after construction of the bridge,
the BHR was 1.0 ("functioning;" Table 1).
Table 1. Stream function categories, based
on bank height ratio
BMP Installed
Near-bank depth (feet)
Mean riffle depth (feet)
Bank height ratio
Stream function category
Before
5.6
1.9
3.0
Not functioning
After
1.8
1.8
1.0
Functioning
Before culvert replacement, the streambed imme-
diately upstream of the road crossing consisted
entirely of fine sand. Although some sand still
remains 3 years after replacement, much has been
transported downstream, lowering the streambed
about 0.5 feet (Figure 3) and exposing coarse gravel.
The median particle size (D50) and the particle
diameter in the 84th percentile (D84) in this reach,
which were visually characterized as 100 percent
fine sand (less than 2 millimeters [mm] in diameter)
before culvert replacement, were substantially
coarser after culvert replacement (D50 = 0.46 mm
[medium sand] and D84 = 28 mm [coarse gravel]).
Further riffle development is expected in this reach
in the coming years.
0 50 100 150 200 250 300 350
Feet along longitudinal profile—upstream to downstream
Figure 3. Overlay graph of longitudinal profile data of Osborn
Creek, before and after culvert replacement. The red
line, which reflects the elevation of the streambed before
restoration, shows a deep plunge pool at the culvert and an
accumulation of sediments on either side. The green line,
which reflects the stream elevation after the culvert was
replaced by the bridge, shows the plunge pool has almost
disappeared, and the accumulated sediment has been
transported downstream.
Finally, migratory salmon and steelhead had been
unable to pass through the culvert, but, since the
bridge was built, they have been sighted by local resi-
dents and U.S. Forest Service personnel upstream of
the Pierce Road crossing.
Partners and Funding
The partners involved in replacing the multiple cul-
verts were the White River Watershed Partnership,
White River Watershed Task Force, Oceana
County Road Commission, KPM Engineering, Land
Conservancy of West Michigan, U.S. Fish and Wildlife
Service, and U.S. Forest Service-Huron-Manistee
National Forest.
Replacing the Pierce Road culvert cost $127,319
in Clean Water Act section 319 grant and match
funds and $93,618 in additional funds from the road
commission, for a total of $220,937. Replacing all
nine culverts totaled $1,173,770 in grant funds and
$945,327 in matching funds, for a total of $2,119,097.
The Michigan Department of Environmental Quality's
Nonpoint Source Unit staff conducted the pre and
post geomorphology monitoring; staff time was
funded with the fiscal year 2012 and 2015 Clean
Water Act section 319 grants.
K1
Ill
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-15-001BBB
November 2015
For additional information contact:
Joe Rathbun
Michigan Department of Environmental Quality
517-284-5517
rathbunj@michigan.gov
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