An Evaluation of Techniques
for Measuring Substrate Embeddedness
by Traci Sylte and Craig
degree to which fine sediments surround coarse substrates on the
surface of a streambed is referred to as embeddedness. Although
the term and its measurement were initially developed to address
habitat space for juvenile steelhead trout, embeddedness measures
have been used to assess fish spawning and macroinvertebrate habitat,
as well as substrate mobility. Embeddedness continues to be used
as an indicator of water quality.
publication provides a comprehensive description of embeddedness,
and the sampling methodology is far from standardized. The information
presented here is derived from a technical note (ERDC TN-EMRRP-SR-36)
produced by the authors under the U.S. Army Corps of Engineers Ecosystem
Management and Restoration Research Program. The technical note
documents definitions and usage of the term “embeddedness,” describes
the development of embeddedness measurement, summarizes the existing
literature, and provides guidelines for the application of measurement
The character of stream substrates is important to both physical
and biological stream functions. In its simplest expression, increased
embeddedness, or the intrusion of fines into a coarse streambed,
decreases the living space between particles and limits the available
area and cover for small fish, macroinvertebrates, and periphyton.
Definitions of Embeddedness
Many definitions of embeddedness exist in the literature. The following
is a brief summary; others exist in the source document:
- “the degree to which cobble larger than
45-mm diameter is embedded in sand (Kelley and Dettman, 1980).
- “the degree that the larger particles
(e.g., boulder, rubble, gravel) are surrounded or covered by fine
sediment” (Platts et al., 1983; Fitzpatrick et al., 1998).
amount of fine sediment that is deposited in the interstices between
larger stream substrate particles” (Burns, 1984; Burns and Edwards,
- “the extent to which larger particles
are buried by fine sediment” (MacDonald et al., 1991).
- “the ‘depth to embeddedness’ is the distance
from the top of the rocks on the bed surface down to the top of
the layer of fines in which the cobbles are embedded” (Osmundson
and Scheer, 1998).
measures the degree to which larger particles are covered with finer
particles – a length term representing a volume of fines surrounding
coarser substrates, which is often placed in a relative proportion
to rock height in the plane of embeddedness (Fig. 1). Moreover,
“fines” are commonly not defined even though the nature and degree
of impact depend upon the size and the character of the sediments
filling interstitial voids. Misconceptions arise because embeddedness
is conceptually appealing as an index of impact even though a precise
consistent definition is lacking.
1. Schematic representation of embeddedness.
Embeddedness Measurement Methods
(1976) and Kelley and Dettman (1980) originally introduced the concept
of embeddedness. Klamt estimated the degree to which key rocks
or dominant rocks in streams were embedded by using 25, 50, and
75 percent embeddedness levels. Kelley and Dettman focused on juvenile
steelhead rearing habitat and quantified the depth of sand particles
surrounding cobble-sized substrate in glide, glide/riffle, and riffle
methods have since been developed to measure or characterize embeddedness
and are summarized in Table 1. Some of these rely on visual estimation
while others measure and compute embeddedness as a percent. Recommended
sample sizes range from as few as 15 to as many as 400 particles.
Sampling may occur at locations that meet specific fish habitat
criteria or span entire stream reaches. Because of this diversity
in technique, comparing embeddedness values from one application
to another is ill advised.
Platts et al.;
Bain & Stevenson
General sample design guidance; no specifics for embeddedness
Thalweg or mid-channel
5 embeddedness classes:0-5, 5-25, 25-50, 50-75, 75-100%
U.S. Environmental Protection Agency EMAP
Kaufmann et al. (1999)
5 estimates at 11 cross-sections
10-cm sampling area at 0, 25, 50, 75, and 100% of cross-sectional
Fitzpatrick et al. (1998)
3 transects;5 gravel to boulder sized substrates examined at each
Nearest 10 percent of embedded depth per particle is averaged
Burns & Edwards
100-400 individual particle depending on desired standard deviation
from the mean
Specific fish habitat depth and velocity criteria
60-cm hoop toss into area meeting depth/velocity criteria;
hoops tossed until sample particle number is attained
Statistically determined; typically 20 random hoops;
3 hoops/transect typically result in @100 samples/transect
to bank transects spanning a reach length of @20 times average stream width
Focused on stream-related questions; improved statistics by averaging
individuals within the hoop and then averaging the transect
U.S. Fish & Wildlife Service
Osmundson et al. (1998)
Minimum of 1 run and riffle/site; specific depth and velocity
criteria wading parallel to shoreline
Measure depth to embeddedness (DTE); 20 DTE are divided by median
rock width of the site and then averaged for the reach
Table 1. Summary of embeddedness methods.
Burns (1984) and Burns and Edwards (1985) essentially developed
the embeddedness measurement method commonly employed. Skille and
King (1989) later advanced the technique to apply it to stream analysis
beyond fish habitat and strengthened its statistical rigor. However,
this work has not been published.
Burns (1984) used embeddedness to refer to the proportion of a large
individual particle that was surrounded by fine sediment. The size
of large particles considered was 4.5 to 30.0 cm in greatest diameter,
and fine sediment was defined as particles less than 6.3 mm diameter.
Burns and Edwards (1985) calculated the proportion by dividing the
embedded depth (De) by the total depth (Dt)
of the particle lying perpendicular to the plane of embeddedness
(Fig. 1). Burns used a 60-cm-diameter steel hoop to define particles
in the substrate to be measured, a 30-cm-transparent ruler to measure
particle dimensions, and a float and a stopwatch to measure water
Embeddedness Application Limits
In 1988, Forest Service fisheries biologists and hydrologists united
to review embeddedness literature, share experiences, and refine
methods. Results of the standardization effort, found only in agency
correspondence documentation, identify several important application
· Cobble embeddedness exhibits high spatial and temporal variability
in both natural and disturbed streams. Sampling must be intensive
to detect changes.
· Cobble embeddedness should be a measured parameter. However, visual
assessments may provide information adequate for characterization
· Embeddedness measurements are most applicable in granitic watersheds
or other geologies where sand is an important component of the annual
sediment load and substrate.
· Cobble embeddedness is best applied to streams where embeddedness
is suspected or known to limit salmonid rearing.
· Repeat monitoring must be conducted at the same site because of
high instream variability.
· Application of the method in streams less than 20 feet wide may
destroy sites for future monitoring(Fig. 2)
· Cobble embeddedness is most appropriate for stream-to-stream comparisons
of similar reaches or for measuring temporal changes in the same
Figure 2. Typical disturbance of the streambed.
Kramer (1989) identified several additional limitations to the embeddedness
methodology and concluded that the techniques developed by Burns
(1984) and Skille and King (1989) failed to accurately portray the
true nature of temporal sediment changes in a channel. Kramer simulated
conditions where fine sediment levels were increased and found that
percent embeddedness actually decreased with increasing fine materials
in some situations. This occurs because rocks that become 100 percent
embedded are no longer measured; i.e., the total rock count is reduced
and calculated percent embeddedness of the sample decreased (Fig.
3. Example of simulated increases in embeddedness that might result
from adding fines from level t1 to t3 that actually results in a
reduction in the calculated embeddedness percentage.
Relation of Embeddedness to Management
ability of embeddedness to detect changes due to land management
activities is unclear and results have rarely been published in
peer reviewed literature. Burns (1984) sampled embeddedness in
19 tributaries of the South Fork of the Salmon River with varying
levels of development. He found that streams with more development
had statistically significant higher mean embeddedness than undeveloped
or partially developed streams. Partially developed and undeveloped
streams were not significantly different from each other. Munther
and Frank (1986) quantified conditions in Montana streams and found
significant differences in only four of eight pairings of habitat
units between developed and undeveloped streams. Potyondy (1993)
in one of the most rigorous of all embeddedness studies summarized
the results of cobble embeddedness analyses conducted on 120 streams
in the Idaho Batholith on the Boise National Forest (Potyondy 1988)
using the Burns (1984) measurement methodology. Potyondy found
no statistical differences among streams in watersheds with various
degrees of land-disturbing impacts from timber harvest, road construction,
grazing, and mining. Stream embeddedness levels appeared to be more
closely related to estimated natural sediment yields related to
geology rather than to management activities occurring in the watersheds.
Few field projects currently use the Burns-Skille-King method. In
the late 1980s and early 1990s, the method was widely used by the
Payette, Boise, Nez Perce, Clearwater, Helena, Deerlodge, Bitterroot,
and Lolo National Forests. We conducted a brief literature review
of the current use of embeddedness in the United States and found
that embeddedness remains a common monitoring technique in at least
17 states and is present as a water quality criterion where legal
implications, such as Total Maximum Daily Load (TMDL) issues, may
Although embeddedness is still widely used as a substrate measurement,
certain negative aspects are apparent. These include the following:
· Significant differences exist in methodologies.
· Published guidance fails to provide the appropriate detail needed
for field application.
· Fundamental defects exist such that a change in approach is necessary.
Without additional research addressing the reliability of embeddedness
outputs from the various methods, use of embeddedness as standards
and guidelines or to link embeddedness to biologic criteria currently
appears highly questionable.
Bain, M. B., and Stevenson, N. J., eds.
(1999). Aquatic habitat assessment: Common methods. American Fisheries
Society, Bethesda, MD.
Burns, D. C. (1984). An inventory of embeddedness
of salmonid habitat in the South Fork Salmon River drainage, Idaho,
Unpublished paper, USDA Forest Service, Payette National Forest,
Burns, D. C., and Edwards, R. E. (1985).
Embeddedness of salmonid habitat of selected streams on the Payette
National Forest, USDA Forest Service, Payette National Forest, McCall,
Fitzpatrick, F. A., Waite, I. R., D’Arconte,
P. J., Meador, M. R., Maupin, M. A., and Gurtz, M. E. (1998). Revised
Methods for Characterizing Stream Habitat in the National Water-Quality
Assessment Program, Water-Resources Investigations Report 98-4052,
U.S. Geological Survey, Raleigh, NC.
Kaufmann, P. R, Levine, P., Robison, E.
G., Seeliger, C., and Peck, D. V. (1999). Quantifying Physical Habitat
in Wadeable Streams, EPA/620/R-99/003. U.S. Environmental Protection
Agency, Washington, DC.
Kelley, D. W., and Dettman, D. H. (1980).
Relationships between streamflow, rearing habitat, substrate conditions,
and juvenile steelhead populations in Lagunitas Creek, Marine County,
1979, Unpublished Report, Marine County Water District, CA.
Klamt, R. R. (1976). The effects of coarse
granitic sand on the distribution and abundance of salmonids in
the central Idaho Batholith, M.S. thesis, University of Idaho, Moscow.
Kramer, R. (1989). Evaluation and revision
of the hoop method for monitoring embeddedness, Unpublished Report,
Lolo National Forest, Missoula, MT.
MacDonald. L. H., Smart, A. S., and Wissmar,
R. C. (1991). Monitoring guidelines to evaluate effects of forestry
activities on streams in the Pacific Northwest and Alaska, EPA/910/9-91-001,
United States Environmental Protection Agency, Water Division, Seattle,
Osmundson, D. B., and Scheer, B. K. (1998).
Monitoring cobble-gravel embeddedness in the streambed of the upper
Colorado River, 1996-1997, Final Report, U.S. Fish and Wildlife
Service, Grand Junction, CO.
Platts, W. S., Megahan, W. F., and Minshall,
W. G. (1983). Methods for evaluating stream, riparian, and biotic
conditions, General Technical Report INT-138, USDA Forest Service,
Rocky Mountain Research Station. Ogden, UT.
Potyondy, J. P. (1988). Boise National Forest
cobble embeddedness baseline inventory: Results and relationship
to management activities, Unpublished Report, Boise NF, Boise, ID.
Potyondy, J. P. (1993). Relationship of
fish habitat condition to management activities on granitic watersheds
in Central Idaho, Hydrological Science and Technology 8(1-4),
Skille, J., and King, J. (1989). Proposed
cobble embeddedness sampling procedure, Unpublished draft, Idaho
Department of Health and Welfare, Division of Environmental Quality,
and USDA Forest Service, Intermountain Research Station, Boise,
Traci Sylte is a Hydrologist, Lolo National Forest,
Missoula, MT; email@example.com; (406) 329-3896.
Craig Fischenich is a Research Civil Engineer, US Army Engineers,
Research and Development Center, Vicksburg, MS; firstname.lastname@example.org;
For more information about embeddedness see: Sylte, T. L., and Fischenich,
J. C. (2002).
for measuring substrate embeddedness,” EMRRP Technical Notes
Collection (ERDC TN-EMRRP-SR-36), U.S. Army Engineer Research
and Development Center, icksburg, MS. Available online at: http://www.wes.army.mil/el/emrrp/pdf/sr36.pdf