1. Page | 1
Proactive By Design.
Our Company Commitment
Mapping and Mitigating Future
Flood Risks for Boston: A
Changing Climate Perspective
Bin Wang, Tianyi Liu, Daniel Stapleton & Chad Cox
ASFPM Annual National Conference 2015

2. Page | 2
OUTLINE
• Background
• Analysis – Storm Surge
Simulations using ADCIRC
• Results – Inundation Mapping
• Takeaways

3. Page | 3
BACKGROUND
Normal Flow
Mean Low Tide
Mean High Tide
Storm Tide (Surge + Tide)
Riverine Flood
Wave Crest ElevationWave
Overtopping
Uplift
Mean Sea Level

4. Page | 4
BACKGROUND
Massachusetts
Bay
Charles River
Boston, MA
Boston Harbor
Cambridge
Back Bay

5. Page | 5
BACKGROUND

6. Page | 6
BACKGROUND
Causes of Coastal Flooding around Boston
Tropical Cyclones (i.e. hurricanes) Extratropical Storms (e.g., nor’easters)

7. Page | 7
BACKGROUND
Museum of
Science
Charles River
Dam

8. Page | 8
BACKGROUND
Source: http://www.nae.usace.army.mil/Missions/CivilWorks/FloodRiskManagement/Massachusetts/CharlesRiverDam.aspx
MOS
Top Elev = 12.2 feet (NAVD) or 12.5 feet (MSL)

9. Page | 9
BACKGROUND
Back Bay
Cambridge
Boston
Digital Elevation Map around Boston

10. Page | 10
BACKGROUND
Source: wikipedia

11. Page | 11
BACKGROUND
http://www.bc.edu/bc_org/avp/cas/fnart/fa267/boston/bos1641.gif

12. Page | 12
BACKGROUND
Astronomical Tides and Storm Tides
Storm Tides (green) - Astronomical Tides (blue) ≈ Storm Surge

13. Page | 13
BACKGROUND
0
1
2
3
4
5
-10
-6
-2
2
6
10
10/28/120:00
10/29/120:00
10/30/120:00
10/31/120:00
StormSurge(feet)
WaterElevation(feet,NAVD88)
Date &Time
StormTides at Boston Harbor during Superstorm Sandy
Predicted (ft) Verified (ft) Storm Surge

14. Page | 14
BACKGROUND
0
1
2
3
4
5
-10
-6
-2
2
6
10
2/6/780:00
2/7/780:00
2/8/780:00
2/9/780:00
StormSurge(feet)
WaterElevation(feet,NAVD88)
Date &Time
StormTides at Boston Harbor during Blizzard 1978
Predicted (ft) Verified (ft) Storm Surge

15. Page | 15
ANALYSIS
Source: http://www.nae.usace.army.mil/Missions/CivilWorks/FloodRiskManagement/Massachusetts/CharlesRiverDam.aspx
Preliminary
November 15, 2013

16. Page | 16
ANALYSIS
Source: http://www.nae.usace.army.mil/Missions/CivilWorks/FloodRiskManagement/Massachusetts/CharlesRiverDam.aspx

17. Page | 17
ANALYSIS
Source: http://www.nae.usace.army.mil/Missions/CivilWorks/FloodRiskManagement/Massachusetts/CharlesRiverDam.aspx

18. Page | 18
ANALYSIS
Source: http://www.nae.usace.army.mil/Missions/CivilWorks/FloodRiskManagement/Massachusetts/CharlesRiverDam.aspx
Factors to consider for modeling
future floods:
• Extreme precipitation (riverine);
• Sea level change (coastal);
• Sea surface temperature (coastal);
• Urban development (riverine &
coastal)

19. Page | 19
ANALYSIS
USACE Sea Level Rise Calculator
+5.0 ft SLR
Current MSL

20. Page | 20
MODELING
Computer Model: ADCIRC+SWAN
• Unstructured mesh
• High resolution
• Coupled circulation and wind-
wave models
• Explicit and implicit solver
Variables and Inputs:
• Topography (land and
bathymetry
• Landuse
• Astronomical tides;
• River flow;
• Sea level change;
• Selected hurricane

21. Page | 21
MODELING
- FEMA Region II ADCIRC Mesh; - Refined for the Boston area

22. Page | 22
MODELING
- Average grid size ~ 20 to 30 m in River and Boston

23. Page | 23
MODELING
Simulated Hurricane Track in ADCIRC
Bearing 10 °
Rmax 35 nm
Vf 20 kt
Vmax 105 kt
DP 68 mb

24. Page | 24
MODELING
List of ADCIRC Runs
Case # Sea Level Charles
River Dam
1 MSL (present) Functional
1a MSL (present) No Dam
2 USACE High SLR Scenario (2100) Functional
2a USACE High SLR Scenario (2100) No Dam
3 USACE High SLR Scenario (2100) Raised 6ft

25. Page | 25
RESULTS
Inundation Map – Case 1

26. Page | 26
RESULTS
Inundation Map – Case 1a

27. Page | 27
RESULTS
Difference: Case 1a - Case 1

28. Page | 28
RESULTS
Inundation Map – Case 2

29. Page | 29
RESULTS
Inundation Map – Case 2a

30. Page | 30
RESULTS
Difference: Case 2a - Case 2

31. Page | 31
RESULTS
Inundation Map – Case 3

32. Page | 32
RESULTS
North Atlantic Coast
Comprehensive Study
0
5
10
15
20
25
1 10 100 1,000 10,000
StillwaterElevation(ft,NAVD88)
Return Period (yr)
Mean Tide Point 9583 (ft, NAVD88)
High Tide Point 9583 (ft, NAVD88)
High Tide + 5' SLR
12.2’±

33. Page | 33
RESULTS
12.2’±
2’± (normal pool)
4.5’±
10’ (100-yr)
11.3’ (500-yr)
15’ ± (100-yr)
17’ ± (500-yr)
Vertical Datum: NAVD88
12’ ± (100-yr)
13’±(500-yr)
Present
Intermediate
SLR
High SLR
MSL
“MSL”
“MSL”

34. Page | 34
TAKEAWAYS
 Significant riverine/coastal flood risks in
Boston and its neighboring towns;
 Charles River Dam protects Boston under
current sea level conditions;
 Larger inundation areas with sea level rise
and climate change;
 Integrated analysis / improvements needed;
 Uncertainty needs to be assessed

35. Page | 35
Bin Wang, P.E.
Technical Specialist
Norwood, MA
781-278-5809
Bin.Wang@gza.com
Tianyi Liu, Ph.D.
Coastal Engineer
Norwood, MA
781-278-3819
Tianyi.Liu@gza.com
Daniel C. Stapleton, P.E.
Principal
Norwood, MA 02062
781-278-5743
Daniel.Stapleton@gza.com
Thank you !

36. Page | 36
TAKEAWAYS
North Atlantic Coast Comprehensive Study