1. 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

2. 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

7. Flow and Lake Level

8. North Combo Middle

10. Pre-Slide Conditions: 100-yr Event C-Post Road Slide Reach

11. Present Conditions: 100-yr Event C-Post Road Slide Reach 279.6 300.2 Current channel alignment and geometry

12. Future: North Alignment - 100yr Event C-Post Road Slide Reach

13. Future: Middle Alignment- 100yr Event C-Post Road Slide Reach

14. Future: Combo Alignment- 100yr Event C-Post Road Slide Reach

15. Future: North Alignment - 100yr Event # Pre-SlidePost-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 285.7300.8 Upstream End of Slide Reach WSE (Pool /Pilot Transition Zone) 279.6300.7 Midway Through Slide Reach WSE 269.3285.1 Downstream End of Slide Reach WSE 265.5266.5 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 287.9289.0290.7293.4 282.9286.5290.0293.1 273.5275.6278.0280.7 265.3265.5265.8266.0 Cut Volume to Match Existing Channel to Specified Geometry (Cu. Yd) 600000463000331000210000

16. Future: Middle Alignment- 100yr Event # Pre-SlidePost-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 285.7300.8 Upstream End of Slide Reach WSE (Pool /Pilot Transition Zone) 279.6300.7 Midway Through Slide Reach WSE 269.3285.1 Downstream End of Slide Reach WSE 265.5266.5 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 288.1288.6289.9292.2 281.0284.4289.0291.8 271.3272.4273.7275.4 265.6265.5265.8266.0 Cut Volume to Match Existing Channel to Specified Geometry (Cu. Yd) 849000710000579000456000

17. Future: Combo Alignment- 100yr Event # Pre-SlidePost-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 285.7300.8 Upstream End of Slide Reach WSE (Pool /Pilot Transition Zone) 279.6300.7 Midway Through Slide Reach WSE 269.3285.1 Downstream End of Slide Reach WSE 265.5266.5 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 287.9289.1290.7293.4 282.9286.5290.0293.1 271.2272.8274.0275.4 265.1265.4265.7265.9 Cut Volume to Match Existing Channel to Specified Geometry (Cu. Yd) 815000663000519000386000

18. Future: 2yr Event – 150’ Wide C-Post Road Slide Reach

19. Future: 2yr Event – 75’ Wide C-Post Road Slide Reach

20. Future: 10yr Event – 150’ Wide C-Post Road Slide Reach

21. Future: 10yr Event – 75’ Wide C-Post Road Slide Reach

22. Excel Summary of Alignment Alternatives

23. Slide developed by Casey Kramer