Building-with-Nature solutions for hurricane flood risk reduction in Galveston Bay

1. 1Challenge the future 1/271/27
Building-with-Nature solutions for hurricane
flood risk reduction in Galveston Bay, Texas
Robert de Boer
November 3, 2015
Deltares NGHS Presentation:

2. 2Challenge the future 2/27
Final Result

3. 3Challenge the future 3/27
Contents
Delft3D Flexible Mesh Model Optimized Design + Conclusions
Introduction
Delft3D FM
Model
Conclusions

4. 4Challenge the future 4/27
1. Introduction
Building-with-Nature solutions for hurricane flood risk reduction
in Galveston Bay, Texas
Source: wikipedia.org
Texas
Source: ian.umces.edu
Galveston Bay (GB)
Houston
Texas City
Galveston
Introduction
Delft3D FM
Model
Conclusions

5. 5Challenge the future 5/27
Source: NY Times
Ike (2008)
1. Introduction
Building-with-Nature solutions for hurricane flood risk
reduction in Galveston Bay, Texas
• Hurricane Ike (Sept, 2008)
• Damage $25-30 billion in US
• Over 100 casualties
Introduction
Delft3D FM
Model
Conclusions

6. 6Challenge the future 6/27
1. Introduction
Building-with-Nature solutions for hurricane flood risk
reduction in Galveston Bay, Texas
• Ike’s aftermath  flood protection plans
• Clear distinction:
1. Large-scale measures (e.g. Ike Dike)
2. Localized measures
• Unique and valuable ecosystem
• Interest for nature-based design
• Opportunities for BwN
Source: texastribune.org
Introduction
Delft3D FM
Model
Conclusions

7. 7Challenge the future 7/27
1. Introduction
Hydraulics
• Flood risk:
• Surge
• Waves
• Variables:
• Landfall location of the hurricane
• Open coast surge level
• Fetch
• Depth
can be affected by measures
Source: Stoeten (2013)
fetch
Introduction
Delft3D FM
Model
Conclusions

8. 8Challenge the future 8/27
1. Introduction
Measures
Introduction
Delft3D FM
Model
Conclusions

9. 9Challenge the future 9/27
2. Delft3D Flexible Mesh Model
Introduction
Delft3D vs Delft3D Flexible Mesh
Introduction
Delft3D FM
Model
Conclusions

10. 10Challenge the future 10/27
2. Delft3D Flexible Mesh Model
Introduction
• Simple hydrodynamic model for rapid assessment
• Goal:
• Model flow and water levels as a result of hurricane
• Evaluate effect of measures on water level
• Ike is the reference hurricane to set-up model
• Assessed for three different hurricanes:
1. Scenario without Ike Dike (Open Bay)
2. Scenario with Ike Dike
Introduction
Delft3D FM
Model
Conclusions

11. 11Challenge the future 11/27
2. Delft3D Flexible Mesh Model
Network
• Fairly coarse resolution
network
• Curvilinear and high
resolution network in deep
channels
• 25,447 netnodes
• 68,025 netlinks
• length ≈ 30 – 3,000 m
Introduction
Delft3D FM
Model
Conclusions

12. 12Challenge the future 12/27
2. Delft3D Flexible Mesh Model
Network
• Measures (islands) implemented by raising bathymetry
Baseline
Introduction
Delft3D FM
Model
Conclusions

13. 13Challenge the future 13/27
2. Delft3D Flexible Mesh Model
Network
• Measures (islands) implemented by raising bathymetry
Measure
Introduction
Delft3D FM
Model
Conclusions

14. 14Challenge the future 14/27
2. Delft3D Flexible Mesh Model
Boundary Conditions
• Small-scale model domain
• Three seaward boundaries forced by hurricane Ike:
• Simulated time-series for points near my offshore boundary
• Interpolated along the boundary
• ADCIRC large-scale Gulf model
• 3.5 day simulation time, from long before to after hurricane Ike
Introduction
Delft3D FM
Model
Conclusions

15. 15Challenge the future 15/27
2. Delft3D Flexible Mesh Model
Spiderweb Wind + Pressure Field
• Spiderweb spherical grid
• UNISYS: storm size, track, core pressure and wind speed
• DelftDashBoard (method 3)
• Default radius of 1000 km, 500 rows and 36 columns
Introduction
Delft3D FM
Model
Conclusions

16. 16Challenge the future 16/27
2. Delft3D Flexible Mesh Model
Model Calibration
• Calibration of peak water level measurements during Ike:
Introduction
Delft3D FM
Model
Conclusions

17. 17Challenge the future 17/27
2. Delft3D Flexible Mesh Model
Hurricanes
• Three different hurricane tracks
1. Ike
2. Ike shifted 25 km to west
3. Ike shifted 40 km to west
Introduction
Delft3D FM
Model
Conclusions

18. 18Challenge the future 18/27
2. Delft3D Flexible Mesh Model
Open Bay: Hurricane Behavior
• Higher surge levels in Galveston Bay for shift 1 and shift 2
• West and Northwest at risk
Introduction
Delft3D FM
Model
Conclusions

19. 19Challenge the future 19/27
2. Delft3D Flexible Mesh Model
Open Bay: Hurricane Behavior
• Shift 2
Introduction
Delft3D FM
Model
Conclusions

20. 20Challenge the future 20/27
2. Delft3D Flexible Mesh Model
Open Bay: Hurricane Behavior
• Maximum inundation for shift 2
Introduction
Delft3D FM
Model
Conclusions

21. 21Challenge the future 21/27
2. Delft3D Flexible Mesh Model
Measures
Residential area
(West)
Port of Houston
(Northwest)
Introduction
Delft3D FM
Model
Conclusions

22. 22Challenge the future 22/27
2. Delft3D Flexible Mesh Model
Open Bay: Surge Reduction of Measures
• Reductions of 0.5-1.0 m are possible for West and Northwest
• Island elevation of 6 m +MSL required
Residential area (West) Port of Houston (Northwest)
Introduction
Delft3D FM
Model
Conclusions

23. 23Challenge the future 23/27
2. Delft3D Flexible Mesh Model
Optimized Design
• Continuous, emerged islands West and Northwest
Residential area
(West)
Port of Houston
(Northwest)
Introduction
Delft3D FM
Model
Conclusions

24. 24Challenge the future 24/27
2. Delft3D Flexible Mesh Model
Optimized Design
• Islands must be emerged and as continuous as possible
• With Ike Dike effect is less
• Combined alternative more effective 1.5-0.5 m:
Without Ike Dike With Ike Dike
Introduction
Delft3D FM
Model
Conclusions

25. 25Challenge the future 25/27
2. Delft3D Flexible Mesh Model
Optimized Design
• Movie water level diffe-
rence for optimized design
during hurricane shift 2
Introduction
Delft3D FM
Model
Conclusions

26. 26Challenge the future 26/27
3. Conclusions
What are the opportunities and limitations of ’Building-with-Nature’ type
solutions to reduce hurricane surge-based flood risk in the Houston
Galveston Bay region?
• BwN solutions should be constructed alongside of ‘hard’ flood risk
reduction measures (e.g. an Ike Dike or levees inside the Bay)
• BwN can reduce flood risk  cannot eliminate flood risk (reduction at
a maximum of 1.5 m)
• Significant intervention in the ecosystem required
• A relatively simple Delft3D FM model for rapid assessment (4 days of
simulation in 2 hours) for hurricane modeling proved to work
reasonably
Introduction
Delft3D FM
Model
Conclusions

27. 27Challenge the future 27/2727/27
Building-with-Nature solutions for hurricane
flood risk reduction in Galveston Bay, Texas
Robert de Boer
November 3, 2015
Deltares NGHS Presentation: