For more information contact: 

CFER Information and Outreach

301M Richardson Hall, OSU USGS Forest and Rangeland 

Corvallis, OR 97331-5752 Ecosystem Science Center

541-737-7612 777 NW 9th St., Suite 400

cfer@fsl.orst.edu Corvallis, OR 97330-6169

http://www.fsl.orst.edu/cfer 541-750-1047

http://fresc.usgs.gov

Authored by Christine May, Robert Gresswell, and Janet Erickson.

Graphics and layout by Gretchen Bracher. Shannon Hayes provided 

graphical assistance on Figure 4.

Scientists who Contributed to this Factsheet

Christine May received her doctoral degree from Oregon State University in December of 2001. Currently she is a post-doctoral researcher in the Department of Earth and Planetary Sciences at the University of California, Berkeley. 

Robert E. Gresswell is an aquatic ecologist with the USGS Forest and Rangeland Ecosystem Science Center and a scientist 

on the CFER research team. 

Research Highlights

• Wood and sediment accumulation rates in the channel were strongly correlated with the time since the previous debris 

flow.

• Large wood was the focal point for sediment accumulation because it provided a physical obstruction to sediment 

transport.

• Sediment that was stored behind wood in the channel increased the streambed roughness, decreased the local slope of 

the channel, and further reduced the capacity for sediment transport.

• With an adequate supply of wood, small streams have potential to store large volumes of sediment in the interval 

between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

For Further Reading

May, C.L. 2001. Spatial and Temporal Dynamics of Sediment and Wood in Headwater Streams in the Central Coast Range. 

PhD dissertation. Corvallis, OR: Oregon State University. 

May, C.L. 2002. Debris flows through different forest age classes in the central Oregon Coast Range. Journal of the American Water Resources Association 38:1097-1113.

May, C.L. and R.E. Gresswell. 2003a. Processes and rates of sediment and wood accumulation in headwater streams of the 

Oregon Coast Range, USA. Earth Surface Processes and Landforms 28:409-424.

May, C.L. and R.E. Gresswell. 2003b. Large wood recruitment 

and redistribution in headwater streams in the southern 

Oregon Coast Range, USA. Canadian Journal of Forest 

Research 33:1352-1362.

May, C.L. and R.E. Gresswell. 2004. Spatial and temporal 

patterns of debris flow deposition in the Oregon Coast 

Range, USA. Geomorphology 57:135-149.

or

This factsheet is one in a series of information products developed by the Cooperative Forest Ecosystem Research (CFER) program on the 

production and function of large wood in the riparian zone. Funding for this research was provided to the CFER program by the Bureau of Land 

Management, USGS Forest and Rangeland Ecosystem Science Center, the Oregon Department of Forestry, and Oregon State University.
accumulates in the channel through time; however, the capacity of the channel to store sediment 

increases, initiating a series of positive feedbacks. 

Sediment that accumulates behind wood in the 

channel increases the streambed roughness, 

decreases the local slope of the channel, and further reduces the capacity for sediment transport. 

On average, 73% of the sediment in these steep, 

debris flow prone channels is stored directly 

behind wood. Because headwater streams occupy 

the majority of the channel length, they have the 

potential to store large volumes of hillslopederived sediment. In an intensive investigation of 

Skate Creek, May and Gresswell found that 72% 

of sediment in the entire drainage network was 

stored in debris flow prone tributaries.

Based on their observations, the researchers created a conceptual diagram that depicts the 

changes in channel morphology that occur in 

headwater streams following a debris flow (Figure 4). Immediately following the disturbance, the 

channel is predominantly bedrock, with almost no 

sediment or wood in storage. During the following 50 years, small discrete patches of sediment 

are stored behind individual logs, but the channel 

remains predominantly bedrock. One hundred 

years after the debris flow almost half of the channel length is still exposed bedrock. By 144 years, the maximum age of channels investigated by May and Gresswell, discrete patches of sediment had coalesced to form larger, more contiguous patches. 

These changes in channel morphology are largely attributable to wood accumulation, which provides the cornerstone for sediment storage in channels that would otherwise remain in a bedrock state.

Figure 2. Volume of large wood in the study streams based 

on the time since the previous debris flow as estimated by 

dendrochronology. 

Figure 3. Sediment accumulation in the study streams based 

on the time since the previous debris flow as estimated by 

dendrochronology. 

N 

300 0 300 600 Meters

Figure 1. Site map of Skate and Bear creeks, Siuslaw River drainage in the 

central Oregon Coast Range. Dark solid lines represent channels investigated 

for wood and sediment storage. Dashed lines represent tributaries impacted 

by timber harvest and not investigated. Thin solid line (ST2) is only 

tributary with no evidence of delivering debris flows to the mainstem. Solid 

circles represent sample sites for the dendrochronology-based fire history 

reconstruction. Contour interval = 10m. 

y = 0.133e 0.015x

r2 = 0.70

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0

25 50 75 100 125 150

Time since debris flow (yrs)

Volume of large wood per

stream length (m3/m) fctsht04/02

y = 0.0014x 1.49

r2 = 0.88

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 25 50 75 100 125 150

Time since debris flow (yrs)

Sediment volume per stream length (m3/m) fctsht04/03
accumulates in the channel through time; however, the capacity of the channel to store sediment 

increases, initiating a series of positive feedbacks. 

Sediment that accumulates behind wood in the 

channel increases the streambed roughness, 

decreases the local slope of the channel, and further reduces the capacity for sediment transport. 

On average, 73% of the sediment in these steep, 

debris flow prone channels is stored directly 

behind wood. Because headwater streams occupy 

the majority of the channel length, they have the 

potential to store large volumes of hillslopederived sediment. In an intensive investigation of 

Skate Creek, May and Gresswell found that 72% 

of sediment in the entire drainage network was 

stored in debris flow prone tributaries.

Based on their observations, the researchers created a conceptual diagram that depicts the 

changes in channel morphology that occur in 

headwater streams following a debris flow (Figure 4). Immediately following the disturbance, the 

channel is predominantly bedrock, with almost no 

sediment or wood in storage. During the following 50 years, small discrete patches of sediment 

are stored behind individual logs, but the channel 

remains predominantly bedrock. One hundred 

years after the debris flow almost half of the channel length is still exposed bedrock. By 144 years, the maximum age of channels investigated by May and Gresswell, discrete patches of sediment had coalesced to form larger, more contiguous patches. 

These changes in channel morphology are largely attributable to wood accumulation, which provides the cornerstone for sediment storage in channels that would otherwise remain in a bedrock state.

Figure 2. Volume of large wood in the study streams based 

on the time since the previous debris flow as estimated by 

dendrochronology. 

Figure 3. Sediment accumulation in the study streams based 

on the time since the previous debris flow as estimated by 

dendrochronology. 

N 

300 0 300 600 Meters

Figure 1. Site map of Skate and Bear creeks, Siuslaw River drainage in the 

central Oregon Coast Range. Dark solid lines represent channels investigated 

for wood and sediment storage. Dashed lines represent tributaries impacted 

by timber harvest and not investigated. Thin solid line (ST2) is only 

tributary with no evidence of delivering debris flows to the mainstem. Solid 

circles represent sample sites for the dendrochronology-based fire history 

reconstruction. Contour interval = 10m. 

y = 0.133e 0.015x

r2 = 0.70

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0

25 50 75 100 125 150

Time since debris flow (yrs)

Volume of large wood per

stream length (m3/m) fctsht04/02

y = 0.0014x 1.49

r2 = 0.88

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 25 50 75 100 125 150

Time since debris flow (yrs)

Sediment volume per stream length (m3/m) fctsht04/03
For more information contact: 

CFER Information and Outreach

301M Richardson Hall, OSU USGS Forest and Rangeland 

Corvallis, OR 97331-5752 Ecosystem Science Center

541-737-7612 777 NW 9th St., Suite 400

cfer@fsl.orst.edu Corvallis, OR 97330-6169

http://www.fsl.orst.edu/cfer 541-750-1047

http://fresc.usgs.gov

Authored by Christine May, Robert Gresswell, and Janet Erickson.

Graphics and layout by Gretchen Bracher. Shannon Hayes provided 

graphical assistance on Figure 4.

Scientists who Contributed to this Factsheet

Christine May received her doctoral degree from Oregon State University in December of 2001. Currently she is a post-doctoral researcher in the Department of Earth and Planetary Sciences at the University of California, Berkeley. 

Robert E. Gresswell is an aquatic ecologist with the USGS Forest and Rangeland Ecosystem Science Center and a scientist 

on the CFER research team. 

Research Highlights

• Wood and sediment accumulation rates in the channel were strongly correlated with the time since the previous debris 

flow.

• Large wood was the focal point for sediment accumulation because it provided a physical obstruction to sediment 

transport.

• Sediment that was stored behind wood in the channel increased the streambed roughness, decreased the local slope of 

the channel, and further reduced the capacity for sediment transport.

• With an adequate supply of wood, small streams have potential to store large volumes of sediment in the interval 

between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

For Further Reading

May, C.L. 2001. Spatial and Temporal Dynamics of Sediment and Wood in Headwater Streams in the Central Coast Range. 

PhD dissertation. Corvallis, OR: Oregon State University. 

May, C.L. 2002. Debris flows through different forest age classes in the central Oregon Coast Range. Journal of the American Water Resources Association 38:1097-1113.

May, C.L. and R.E. Gresswell. 2003a. Processes and rates of sediment and wood accumulation in headwater streams of the 

Oregon Coast Range, USA. Earth Surface Processes and Landforms 28:409-424.

May, C.L. and R.E. Gresswell. 2003b. Large wood recruitment 

and redistribution in headwater streams in the southern 

Oregon Coast Range, USA. Canadian Journal of Forest 

Research 33:1352-1362.

May, C.L. and R.E. Gresswell. 2004. Spatial and temporal 

patterns of debris flow deposition in the Oregon Coast 

Range, USA. Geomorphology 57:135-149.

or

This factsheet is one in a series of information products developed by the Cooperative Forest Ecosystem Research (CFER) program on the 

production and function of large wood in the riparian zone. Funding for this research was provided to the CFER program by the Bureau of Land 

Management, USGS Forest and Rangeland Ecosystem Science Center, the Oregon Department of Forestry, and Oregon State University.