Damage to Watershed Research Facilities on the H.J. Andrews
Experimental Forest Part of the Willamette National Forest Near
Blue River, Oregon, Lane and Linn County, February 6 & 8, 1996
Heavy rainfall during the storm of February 6-9, 1996, contributed to
extremely large flows which triggered several debris avalanches that
destroyed and completely covered one experimental gaging station and
sediment basin and contributed substantial damage to several others.
Experimental Watershed #3
Damage
- The Watershed 3 Gage House was completely destroyed and carried
- The sediment basin destroyed and/or covered with many cubic
yards of debris.
- The water measurement control flume is covered and may be
destroyed with many cubic yards of debris.
- The gravel access road was completely covered.
Expected excavation and repair costs
- Excavation for new access road, flume site, and bedload
basin (rough estim. 5,000 yds @ S4.00/yd.) = $20,000
- Construction of new gage house = $20,000
- Concrete 120 degree trapezoidal flume reconstruction = $15,000
- Streamflow/nutrient/sediment monitoring instrumentation = $ 25,000
- Bedload basin reconstruction = $20,000
- Access road reconstruction = $5,000
- Subtotal = $105,000
Experimental Watershed #2
Damage
- Bedload measuring basin filled with sediment overflowed the
control structure.
Expected repair costs
- Excavation of basin control section and debris in basin = $5,000
- Construction of control section and emptying ramp = $15,000
- Subtotal = $20,000
Experimental Watershed #1 Damage
Damage
- High flows destroyed the intake and out flow controls to the
sediment basin filled entire basin with debris.
Expected repair costs
- Excavation and reconstruction of new approach and out
flow controls to basin = $30,000
Experimental Watershed #9
Damamge
- High flows exerted excess pressure to retaining log on the bedload
measurement basin cracking the log.
Expected repair costs
- Replacement of the bedload basin dam = $8,000
Experimental Watershed #10
Damage
- Debris avalanche came down the channel stacked debris up against
the gage
house, incapacitated the flume, damaged the nutrient sampling
structure, and filled and overflowed the bedload measurement basin.
Expected repair costs
- 1. Excavation and repair to the sediment basin = $10,000
- 2. Repair to the gage house and nutrient sampling structures = $5,000
- Subtotal = $15,000
Experimental Watershed #6 and #7
Damage
- High flows and stream transport of excessive bedload filled and
damaged these H-Flume type structures there.
Estimated repair costs
- These structures were not immediately accessible, but the
expected replacement cost of these structures is $11,000 each
(total = $22,000)
Experimental Stream Gage, Sampling Station, and Fish Ladder at Mack
Creek
Damage
- 1. Extremely high flows dislodged the nutrient/sediment sampling
intake and
washed it away, also causing damage to the interior sampling device.
- 2. Excessive gravels, boulders, and debris were lodged in front of
the fish ladder intake.
Expected repair cost
- 1. Repair to the water sampling equipment = $7,000
- 2. Removal of debris to fish ladder and reestablishment of
channel = $3,000
- Subtotal = $10,000
TOTAL EXPECTED REPAIR COSTS = $200,000
*** - These are rough estimates of repair as haul distances for
excavated material have not been determined and many of the damaged
facilities are still covered with debre.