Gregory Indivero 31 October 2011
What discharge (cfs) is required to entrain the D 84 (84 th percentile of sediment size distribution) in Red Canyon Wash? What discharge was required to deposit observed flood debris from August 16, 2010 flood?
Red & Columbus Canyons Un-gauged, Ephemeral Wash 5 th Largest Drainage of CNM
Red Canyon Wash Study Reach
Fairly Straight Alluvial Channel 300 Feet Long 20 Feet Wide
Establish Reach & Cross Sections Survey Thalweg, Flood Debris & Cross Sections Conduct a Pebble Count at Cross Sections Create Grain Size Distribution Plots Solve Shields Equation for Critical Shear Stress, τ c Model Channel With HEC-RAS -Fluctuate Discharge In Channel Until τ c Is Achieved -Fluctuate Discharge Until Flood Debris Elevation is Achieved
Run Tape Measure down the Thalweg Establish Bench Mark Photo Credits: Gigi Richard
Elevation in Feet Surveying the Thalweg o Slope = 0.0261 Red Canyon Wash Long Profile 4938 4936 4934 4932 4930 4928 4926 Red Canyon Wash Thalweg Energy Gradient (Slope) 0 50 100 150 200 250 300 350 y = -0.0261x + 4935.3 Dis tance Downstream in Feet R² = 0.9846 Photo Credit: Gigi Richard
Surveying Cross Section 1 Surveying Cross Section 3 Photo Credits: Gigi Richard
Elevation in Feet Elevation in Feet 4939 4938 Cross Section 1 4937 4936 4935 4934 4933 4932 0 10 20 30 40 50 60 ocross Sections 1 & 3 124 Feet Apart Dis tance From Left B ank in Feet 4934 4933 Cross Section 3 4932 4931 4930 0 5 10 15 20 25 30 35 40 45 50 Distance From Left Bank in Feet
Percent Finer Red Canyon Wash 100 90 80 70 60 50 40 30 Cross Section 1 Cross Section 2 Cross Section 3 20 10 0 1 10 100 1000 Particle Diameter (mm) 100 Grains Counted At Each Cross Section Average D 84 = 24 mm
Shields Equation τ c = τ * c(ρ s ρ w )gd 84 Where: τ * c = Dimensionless Shear Stress ρ s, ρ w = Density of Sediment (Quartz) & Water Respectively g = Gravitational Constant D 84 = 84 th Percentile of Grain Size Distribution τ c = 0.045(9.81 m/s 2 )(2650-1000 kg/m 3 )(0.024 m)
HEC-RAS Model At Cross Section 1 Q = 4 ft 3 /s Distance From Left Bank (ft) Channel Forming Discharge = 4 cubic Feet per Second Frequency =??
What was the discharge of this flow? Photo Credits: Teri Lindaur
Elevation in Feet Surveyed High Water Mark Using Flood Debris Indicators 4938 Red Canyon Wash Long Profile With High Water Mark 4936 4934 4932 4930 4928 4926 Red Canyon Wash Thalweg REW LEW Energy Gradient (Slope) 0 50 100 150 200 250 300 350 Dis tance Downstream in Feet y = -0.0261x + 4935.3 R² = 0.9846 Photo Credits: Gigi Richard
HEC-RAS Model At Cross Section 1 Flood Debris Q = 200 ft 3 /s Distance From Left Bank (ft) Discharge of Flood on August 16, 2010 200 cubic feet per second
Photo Credits: Greg Indivero
Video Credits: Teri Lindaur
How often do these types of flows occur? Speculation Historical Events (September 7, 1978 2,890 cfs) Photo Credits: Jim Johnson
A Big Thank You Goes Out to the following: Dr. Gigi Richard Mrs. Teri Lindaur Mr. Con Trumbull Ms. HeidlHausner Mr. Frank Jacobs
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