The Portland General Electric (PGE) Bull Run Hydroelectric Project was decommissioned beginning in 2007. A series of studies were initiated to predict and/or monitor the effects of the removal of Marmot Dam in 2007 and the Little Sandy Dam in 2008.
The following are different projects of the sub-type Little Sandy Dam/Marmot Dam Removal Effects that have occurred in the Sandy River Basin. Click on the "Show Details" link at the bottom of any project entry to see the full details for that project.
USGS equal-width integrated samples of bedload at stations 14136500, 14137002, 14142500, and at rivermile 5.9 beginning Sept. 07
Bedload measurements indicate the quantity and size distribution of non-suspended particles being moved by a river or stream's current past a given point per unit of time. Equal-width integrated samples of bedload were taken at several sites along the Sandy River, generally associated with gaging stations. The results help document the downstream movement of sediments released by the removal of Marmot Dam.
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Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
Longitudinal and cross-sectional transects to show changes in bed elevation associated with dam removal.
The Little Sandy Dam was removed in 2008. Cross-sectional and longitudinal transects measured below the dam site before and after dam removal will be compared to look for down-cutting or aggradation of the stream bed. The results will guide managers in their restoration efforts.
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There are no reports or data for this project.
Detailed description of the erosion of the sediment wedge behind Marmot Dam immediately following dam removal
A knickpoint is the leading edge of the erosion of a stream channel, appearing as a sudden break in channel gradient. This study documented the upstream migration of the knickpoint through reservoir sediments after the breaching of the Marmot Dam coffer dam. Results will help scientists and engineers understand how river channels are likely to behave after dam removals elsewhere in mountain streams.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
Visual surveys and qualitative assessments of Lower Sandy sites after 2000 lahar flows. Pebble counts at three sites comparing 1999 to 2001 (Stillwater for PGE).
The size composition of river-bed substrates were surveyed at various sites in the Sandy River after a lahar flow event in 2000. The results were compared with those of similar surveys conducted before the lahar flows. The comparison illustrated what could happen when the removal of Marmot Dam in 2008 released a wedge of sediment built up behind the dam.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
Geo-referenced time-lapse photographs of sediment deposits before and after dam breach
Geo-referenced photopoints were established at five points immediately upstream of and downstream of the Marmot Dam site for time-lapse photography. They visually document changes to the river channel associated with the removal of Marmot Dam.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
Prediction of sediment distribution following Marmot Dam removal by following sediments from 2000 lahar flows in 2002-3.
PhD dissertation. The sediment storage potential of the Sandy River below Marmot Dam was estimated using field measurements of sheer stress and patterns of deposition following a lahar flow event in 2000. The results were intended, among other things, to indicate what could happen when the removal of Marmot Dam in 2008 released a wedge of sediment built up behind the dam.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
Detailed cross-section data from areas upstream and downstream of Marmot Dam site that may be affected by scouring and deposition of dam sediment.
A series of cross-sections were established both upstream and downstream of the Marmot Dam site before it was removed. Annual resurveying of these cross-sections will characterize how the removal of Marmot Dam affects the scouring and deposition of river-bed sediments. The results will help establish the effects of dam removal on river-channel complexity.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
11-12 Wolman pebble counts above and below Marmot Dam site collected by Stillwater Sciences. Prior to 2000? Seven sites graphically summarized in "Numerical Modeling of Sediment Transport in the Sandy River, OR, Following Removal of Marmot Dam"-Tech.Report for PGE by Stillwater Sciences, March 2000.
Wolman pebble counts are used to characterize the relative abundance of rock particles of various sizes on the surface of the riverbed. The size of particles are measured at regular intervals across the width of the channel. The results were used to predict and prepare for the consquences of the removal of Marmot Dam.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
Measurements of sediments at various locations over time.
Riverbed sediments have been measured at various locations in the Sandy River to monitor the movement of particles from the sediment wedge behind Marmot Dam after dam removal.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
USGS equal-width integrated samples of suspended sediment at stations 14136500, 14137002, 14142500, and at rivermile 5.9 beginning Sept. 07
Suspended sediment measurements indicate the quantity and size distribution of suspended particles being moved by a river or stream's current past a given point per unit of time. Equal-width integrated samples of suspended sediment were taken at several sites along the Sandy River, generally associated with gaging stations. The results help document the downstream movement of sediments released by the removal of Marmot Dam.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
USGS continuous turbidity measurements at stations 14137002 (2 years).
Turbidy is a measure of the cloudiness of water, caused by suspended particles preventing the passage of light by deflecting it (as opposed to absorbing it, which happens when decaying vegetation tints the water). Turbidity was monitored continuously for about two years to investigate the effects of the removal of Marmot Dam, and the subsequent release of sediment stored behind it.
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Reports and Data
Please note: Not all reports and data below cover all the above reaches. If you are interested in only a particular reach please click on it's name above to access information applicable to only that reach.
