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 Columbus Canyon Red Canyon Wash Study Reach No Thoroughfare Canyon
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
Surveying the Thalweg o Slope = Photo Credit: Gigi Richard
Surveying Cross Section 1 Surveying Cross Section 3 Photo Credits: Gigi Richard
o Cross Sections 1 & Feet Apart
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
Channel Forming Discharge = 4 cubic Feet per Second Frequency = ?? Distance From Left Bank (ft) HEC-RAS Model At Cross Section 1 Q = 4 ft 3 /s
What was the discharge of this flow? Photo Credits: Teri Lindaur
Surveyed High Water Mark Using Flood Debris Indicators Photo Credits: Gigi Richard
Discharge of Flood on August 16, 2010 ≈ 200 cubic feet per second Distance From Left Bank (ft) HEC-RAS Model At Cross Section 1 Q = 200 ft 3 /s Flood Debris
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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