1. The Effects of Starting Wave Conditions on Coastal Flood Hazards: A Sensitivity Analysis for the Texas Coast Katrina Myers, PE, CFM Guillermo Simón, PE, CFM

2. Outline BackgroundWHAFIS Setup Starting Wave Conditions Findings

3. Past FEMA Projects

4. Texas Coastal Projects Subcontractor to Halff & Associates Aransas County Calhoun County Jackson County Matagorda County Refugio County Victoria County Prime Contractor Galveston County Subcontractor to Halff & Associates Aransas County Calhoun County Jackson County Matagorda County Refugio County Victoria County Prime Contractor Galveston County

5. FIS and DFIRM Coastal mapping WHAFIS modeling

6. Welcome to Galveston

7. Development Coastal Structures Welcome to Galveston Bays

8. Long History of Storms… Ike 2008 1915 1900 Carla 1961 Carla 1961 Alicia 1983 Alicia 1983

9. Long History of Storms…

10. WHAFIS Overview

11. Transects

12. USACE Storm Surge

13. Land Cover

14. Topography/Bathymetry

15. Starting wave conditions Fetch STWAVE Hindcast Data Options

16. Starting Wave Conditions: Fetch

17. Starting Wave Conditions: STWAVE U.S. Army Corps of Engineers, (2010). “Flood Insurance Study: Coastal Counties, Texas.” Intermediate Submission 1: Scoping and Data Review. − STWAVE− WAM− ADCIRC

18. Starting Wave Conditions: STWAVE 2D wave model, uses output from model surface as WHAFIS starting wave height and period.

19. STWAVE T p

20. Starting Wave Conditions: Hindcast Data Hourly wave data from WIS stations

21. Starting Wave Conditions: Hindcast Data

24. Relationship Between T p and H mo

25. Overview Map

26. Coastal Analyst Taylor Engineering-developed GIS tool for WHAFIS modeling and mapping

27. Transect 18

28. Gulf T18, Starting Conditions T p (sec)H c (ft) Fetch6.449.48 Hindcast Data12.2110.45 STWAVE11.4510.45 Ground0 ft NAVD Stillwater13.40 ft NAVD Depth Limited Wave Height 10.45 ft

29. Gulf T18, Buildings Wave Crest Elevation

30. Gulf T18, Open Water Wave Crest Elevation

31. Gulf T18, Marsh Wave Crest Elevation

32. Transect 18

33. Bay T18, Bay Shoreline T p (sec)H c (ft) Fetch6.928.89 Bay Fetch3.877.34 Hindcast Data12.219.26 STWAVE11.459.22 Bay STWAVE5.38.45 Stillwater14.05 ft NAVD Depth Limited Wave Height 10.96 ft Fetch Length3.16 miles

34. Bay T18, Bay Shoreline Wave Crest Elevation

35. Conclusions Higher Wave Period from STWAVE and Hindcast Data compared to fetch No difference after transect crosses high ground/ above surge areas Very little difference on wave crest elevation for areas where wave is dampened by buildings or trees

36. Conclusions Less than 0.5ft difference in areas where wave is regenerating in marsh and open water Larger differences between transects originating in the bay compared to the Gulf Potential impact on wave runup

37. Thank you