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Roughness of Floodplain Plants Using Plants to Improve Flood Management What Is Roughness?

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Roughness of Floodplain Plants Using Plants to Improve Flood Management What Is Roughness? Roughness of Floodplain Plants Using Plants to Improve Flood Management What is Roughness? Texture Friction Blockage Resistance to flow Plants have roughness So do the Things we Put in channels We measure roughness using Mannings n – a number used in a whole bunch of hydraulic analyses 2/3 1/2 n=(1/v)R Sf R= hydraulic radius Sf= friction slope V = water velocity Manning's n Coefficients for Open Channel Flow The fluid mechanics calculations website Manning n has no units. Material Manning n Material Manning n Natural Streams Excavated Earth Channels Clean and Straight 0.030 Clean 0.022 Major Rivers 0.035 Gravelly 0.025 Sluggish with Deep Pools 0.040 Weedy 0.030 Stony, Cobbles 0.035 Metals Floodplains Brass 0.011 Pasture, Farmland 0.035 Cast Iron 0.013 Light Brush 0.050 Smooth Steel 0.012 Heavy Brush 0.075 Corrugated Metal 0.022 Trees 0.15 Non-Metals Glass 0.010 Finished Concrete 0.012 Clay Tile 0.014 Unfinished Concrete 0.014 Brickwork 0.015 Gravel 0.029 Asphalt 0.016 Earth 0.025 Masonry 0.025 Planed Wood 0.012 Unplaned Wood 0.013 Minimum Normal Maximum Type of Channel and Description Natural streams - minor streams (top width at floodstage < 100 ft) 1. Main Channels 0.025 0.030 0.033 a. clean, straight, full stage, no rifts or deep pools 0.030 0.035 0.040 b. same as above, but more stones and weeds 0.033 0.040 0.045 c. clean, winding, some pools and shoals 0.035 0.045 0.050 d. same as above, but some weeds and stones e. same as above, lower stages, more ineffective 0.040 0.048 0.055 slopes and sections f. same as "d" with more stones 0.045 0.050 0.060 g. sluggish reaches, weedy, deep pools 0.050 0.070 0.080 h. very weedy reaches, deep pools, or floodways 0.075 0.100 0.150 with heavy stand of timber and underbrush 2. Mountain streams, no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stages a. bottom: gravels, cobbles, and few boulders 0.030 0.040 0.050 0.040 0.050 0.070 b bottom: cobbles with large boulders Mannings n – average of all textures, but used as a model fitting parameter. Inaccuracy in other model parameters: Shape, channel form, grade, slope, sinuosity, velocity, water density, … get assigned to roughness O’Connor Lakes, Star Bend Lots of variation: ∆ velocity = ∆ roughness Pre‐project velocities The need for improving safety and ecosystem management prompted us to look at the role some common plants play in creating roughness. Plants selected because they are adapted to flooding, are common in our floodways, and provide good habitat value Mulefat Wild Rose Sandbar willow California Blackberry x= 47' x=33' x=19' Flume tail tank 6’ H V Depth Control 2’ Weir x =60' C B A x =0' Pumps Point gage locations and velocity measurement sections Velocity measurement locations in a cross-section Flume width 5 ft Flume width 5 ft 6 ft 6 ft 8 ft 8 ft 2 ft 2 ft 4 ft bin Width 4 ft bin Width Water depth Water depth higher than 2 ft lower than 2 ft Velocity and Water Surface Profiles V Scale X 19.5 33.5 47 2 Z 2.65 2.54 2.56 2.17 4.39 4.69 4.86 1.67 4.18 4.56 4.64 V (ft/s) 1.17 4.11 4.42 4.44 0.67 4.00 4.20 4.03 0.25 3.62 3.47 3.36 8.00 7.00 Flow Regime S15 6.00 5.00 V= 2 ft/s 4.00 3.00 Elevation [ft] Elevation 2.00 1.00 0.00 0 10203040506070 X [ft] Water Surface Flume Top Elevation Bottom Elevation Velocity at P#2 Velocity at P#3 Velocity at P#4 STREAMBED BARE SOIL SAMPLE PREPARATION Sandbar Willow 1st replicate Sandbar Willow 3rd replicate Velocity Profile Sandbar Willow V=1.5 ft/s H=1.5 ft V=3.0 ft/s H=1.5 ft 5 5 V|x=16ft V|x=16ft V|x=34ft V|x=34ft 4 V|x=47ft 4 V|x=47ft 3 3 Z(ft) Z(ft) 2 2 1 1 0 0 02460246 Velocity (ft/s) Velocity (ft/s) Velocity Profile Sandbar Willow V=1.5 ft/s H=5 ft V=3.0 ft/s H=5 ft 5 5 V|x=16ft V|x=16ft V|x=34ft V|x=34ft 4 V|x=47ft 4 V|x=47ft 3 3 Z(ft) Z(ft) 2 2 1 1 0 0 02460246 Velocity (ft/s) Velocity (ft/s) Velocity Profile Sandbar Willow V=4.5 ft/s H=3 ft V=6.0 ft/s H=3 ft 5 5 V|x=16ft V|x=16ft V|x=34ft V|x=34ft 4 V|x=47ft 4 V|x=47ft 3 3 Z(ft) Z(ft) 2 2 1 1 0 0 02460246 Velocity (ft/s) Velocity (ft/s) Roughness Coefficient vs Reynolds Number Sandbar Willow 0.09 Bare Soil 0.08 0.07 Willow1 0.06 Willow2 0.05 Willow3 ng's n ng's 0.04 Linear (Bare Soil) Manni 0.03 Linear (Willow1) 0.02 Linear (Willow2) 0.01 Linear (Willow3) 0.00 0 200,000 400,000 600,000 Re Velocity Profile Mulefat V=4.5 ft/s H=3ft V=6 ft/s H=3 ft 5 5 V|x=16ft V|x=16ft V|x=34ft V|x=34ft V|x=47ft V|x=47ft 4 4 3 3 (ft) (ft) hh hh Dept Dept 2 2 1 1 0 0 02460510 Velocity (ft/s) Velocity (ft/s) Comparative Roughness: Mulefat & Sandbar Willow 0.12 Bare Soil Willow (March) Willow (April) 0.10 Willow (May) Mule Fat (Nov-Dec) Mule Fat (Oct-Nov) Linear (Bare Soil) Linear (Willow (March)) 0.08 Linear (Willow (April)) Linear (Willow (May)) Linear (Mule Fat (Nov-Dec)) Linear (Mule Fat (Oct-Nov) ) 0.06 ning's n Man 0.04 0.02 0.00 0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 Re Velocity Profile California Blackberry V=3 ft/s Ht=5ft V=6 ft/s Ht=3.4ft 6 6 V|x=16ft V|x=16ft V|x=34ft V|x=34ft 5 V|x=47ft 5 V|x=47ft 4 4 (ft) t (ft) tt 3 hh 3 Heig Heigh 2 2 1 1 0 0 0.0 2.0 4.0 6.0 0.0 2.0 4.0 6.0 Velocity (ft/s) Velocity (ft/s) Roughness coefficients vs Reynolds Number California Blackberry 0.16 Blackberry(Mar) Blackberry(Apr) 0.14 Blackberry(May) Willow (March) Willow (April) Willow (May) 0.12 Mule Fat (Oct-Nov) Mule Fat (Nov-Dec) Mule Fat (January) Mule Fat (February) 0.10 Bare Soil Linear (Blackberry(Mar)) Linear (Blackberry(Apr)) g's n Linear (Blackberry(May)) nn 0080.08 Manni 0.06 0.04 0.02 0.00 0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 Re Velocity profile Wildrose V=4.5ft/s H=3ft V=6ft/s H=3.4ft 6 6 V|x=16ft V|x=16ft V|x=34ft V|x=34ft 5 V|x=47ft 5 V|x=47ft 4 4 3 3 depth (ft) depth (ft) rr Wate Water Water 2 2 1 1 0 0 02468 02468 Velocity (ft/s) Velocity (ft/s) Mannings Coefficient vs Reynolds Number Rose and Blackberry 0.16 Blackberry(Mar) Blackberry(Apr) Blackberry(May) Willow (March) 0.14 Willow (April) Willow (May) Mule Fat (Oct-Nov) Mule Fat (Nov-Dec) Mule Fat (January) Mule Fat (February) 0.12 Bare Soil Wildrose#1(Jun) Wildrose#2(Jun) Wildrose#3(Jul) Linear (Blackberry(Mar)) 0.10 Linear (Blackberry(Apr)) Linear (Blackberry(May)) n Linear (Wildrose#1(Jun)) ss Linear (Wildrose #2(Jun )) Linear (Wildrose#3(Jul)) 0.08 Manning' 0.06 0.04 0.02 0.00 0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 Re Erosion Summary Erosion (in) Bare soil 3 2 mulefat rose 1 willow 1 3 5 Velocity (ft/sec) Swim Response to Sandbar Willow ○ = TBF Swim Chamber ● = MO2 ■ =TBF Flume (3.0 ft/s) (1. 5 ft/s) (0.5 ft/s) A Mosaic of Plants As built – velocity .
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