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Travis Ball, PE USACE Seattle Hydraulic Engineering Section 2 May 2014 HWY 530 Landslide: Hydraulic Modeling in Support of County, State, and Federal Long-Term Planning
Travis Ball, PEUSACE SeattleHydraulic Engineering Section2 May 2014
HWY 530 Landslide: Hydraulic Modeling in Support of County, State, and Federal Long-Term Planning
FEMA’s Hydraulic Modeling Effort: Mission Assigned to USACE
1. Planning-level modeling to help inform decision makers about long-term flood risks and channel alignment/geometry alternatives
2. Continue and add to the long-term modeling effort that will be ongoing by various parties for several months
Flow and Lake Level
North Combo
Middle
90000 95000 100000 105000
240
260
280
300
DEM2013XSsGeom: 2013XSs
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 100yr
Ground
NFStillaguamish NFStillaguamish
Pre-Slide Conditions: 100-yr Event
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Slide Reach
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invertGeom: Base+PilotGeo=40'wide270'invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 100yr - DEM2013XSs
WS 100yr - Pilot40'w270'invert
Ground
NFStillaguamish NFStillaguamish
Present Conditions: 100-yr Event
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Slide Reach
279.6
300.2
Current channel alignment and geometry
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) North100% 4) North75% 5) North50% 6) North25%Geom: Base+PilotGeo=40'wide270' invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 100yr - DEM2013XSs
WS 100yr - Pilot40'w270'invert
WS 100yr - North100%
WS 100yr - North75%
WS 100yr - North50%
WS 100yr - North25%
Ground
NFStillaguamish NFStillaguamish
Future: North Alignment - 100yr Event
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Slide Reach
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) Mid100% 4) Mid75% 5) Mid50% 6) Mid25%Geom: Base+PilotGeo=40'wide270'invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 100yr - DEM2013XSs
WS 100yr - Pilot40'w270'invert
WS 100yr - Mid100%
WS 100yr - Mid75%
WS 100yr - Mid50%
WS 100yr - Mid25%
Ground
NFStillaguamish NFStillaguamish
Future: Middle Alignment- 100yr Event
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Slide Reach
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) Combo100% 4) Combo50% 5) Combo75% 6) Combo25%Geom: Base+PilotGeo=40'wide270' invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 100yr - DEM2013XSs
WS 100yr - Pilot40'w270'invert
WS 100yr - Combo100%
WS 100yr - Combo50%
WS 100yr - Combo75%
WS 100yr - Combo25%
Ground
NFStillaguamish NFStillaguamish
Future: Combo Alignment- 100yr Event
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Future: North Alignment - 100yr Event
# Pre-Slide Post-Slide
1% Flood Event (100-year: 34,103 cfs) FEMA Hydraulic
Model with 2013 LiDAR and no Bathymetry
Baseline: Using Observed Data
on/around 4/23/2014
C-Post WSE 285.7 300.8
Upstream End of Slide Reach WSE (Pool /Pilot
Transition Zone) 279.6 300.7Midway Through Slide
Reach WSE 269.3 285.1Downstream End of
Slide Reach WSE 265.5 266.5
Long Term Measure Runs for Modifications to Existing (North Alignment) Channel
Base Width of 150 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions**
Base Width of 125 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions
Base Width of 100 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions
Base Width of 75 Feet, 2:1 Side Slopes, and
Elevation (variable) Equal to PreSlide
Conditions
287.9 289.0 290.7 293.4
282.9 286.5 290.0 293.1
273.5 275.6 278.0 280.7
265.3 265.5 265.8 266.0
Cut Volume to Match Existing Channel to Specified Geometry (Cu. Yd) 600000 463000 331000 210000
Future: Middle Alignment- 100yr Event
# Pre-Slide Post-Slide
1% Flood Event (100-year: 34,103 cfs) FEMA Hydraulic
Model with 2013 LiDAR and no Bathymetry
Baseline: Using Observed Data
on/around 4/23/2014
C-Post WSE 285.7 300.8
Upstream End of Slide Reach WSE (Pool /Pilot
Transition Zone) 279.6 300.7Midway Through Slide
Reach WSE 269.3 285.1Downstream End of
Slide Reach WSE 265.5 266.5
Long Term Measure Runs for Middle Channel Development
Base Width of 150 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions**
Base Width of 125 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions
Base Width of 100 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions
Base Width of 75 Feet, 2:1 Side Slopes, and
Elevation (variable) Equal to PreSlide
Conditions
288.1 288.6 289.9 292.2
281.0 284.4 289.0 291.8
271.3 272.4 273.7 275.4
265.6 265.5 265.8 266.0
Cut Volume to Match Existing Channel to Specified Geometry (Cu. Yd) 849000 710000 579000 456000
Future: Combo Alignment- 100yr Event
# Pre-Slide Post-Slide
1% Flood Event (100-year: 34,103 cfs) FEMA Hydraulic
Model with 2013 LiDAR and no Bathymetry
Baseline: Using Observed Data
on/around 4/23/2014
C-Post WSE 285.7 300.8
Upstream End of Slide Reach WSE (Pool /Pilot
Transition Zone) 279.6 300.7Midway Through Slide
Reach WSE 269.3 285.1Downstream End of
Slide Reach WSE 265.5 266.5
Long Term Measure Runs for Combo Channel Development
Base Width of 150 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions**
Base Width of 125 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions
Base Width of 100 Feet, 2:1 Side Slopes,
and Elevation (variable) Equal to
PreSlide Conditions
Base Width of 75 Feet, 2:1 Side Slopes, and
Elevation (variable) Equal to PreSlide
Conditions
287.9 289.1 290.7 293.4
282.9 286.5 290.0 293.1
271.2 272.8 274.0 275.4
265.1 265.4 265.7 265.9
Cut Volume to Match Existing Channel to Specified Geometry (Cu. Yd) 815000 663000 519000 386000
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) North100% 4) Mid100% 5) Combo100%Geom: Base+PilotGeo=40'wide270' invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 2yr - DEM2013XSs
WS 2yr - Pilot40'w270'invert
WS 2yr - North100%
WS 2yr - Mid100%
WS 2yr - Combo100%
Ground
NFStillaguamish NFStillaguamish
Future: 2yr Event – 150’ Wide
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Slide Reach
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) North25% 4) Mid25% 5) Combo25%Geom: Base+PilotGeo=40'wide270' invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 2yr - DEM2013XSs
WS 2yr - Pilot40'w270'invert
WS 2yr - North25%
WS 2yr - Mid25%
WS 2yr - Combo25%
Ground
NFStillaguamish NFStillaguamish
Future: 2yr Event – 75’ Wide
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Slide Reach
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) North100% 4) Mid100% 5) Combo100%Geom: Base+PilotGeo=40'wide270'invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 10yr - DEM2013XSs
WS 10yr - Pilot40'w270'invert
WS 10yr - North100%
WS 10yr - Mid100%
WS 10yr - Combo100%
Ground
NFStillaguamish NFStillaguamish
Future: 10yr Event – 150’ Wide
C-Po
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Slide Reach
85000 90000 95000 100000
240
260
280
300
1) DEM2013XSs 2) Pilot40'w270'invert 3) North25% 4) Mid25% 5) Combo25%Geom: Base+PilotGeo=40'wide270'invert
Main Channel Distance (ft)
Ele
vatio
n (ft
)
Legend
WS 10yr - DEM2013XSs
WS 10yr - Pilot40'w270'invert
WS 10yr - North25%
WS 10yr - Mid25%
WS 10yr - Combo25%
Ground
NFStillaguamish NFStillaguamish
Future: 10yr Event – 75’ Wide
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Slide Reach
Excel Summary of Alignment Alternatives
Slide developed by Casey Kramer
