1. Flood Mapping Across the Pond: A Comparison of Programs and Technical Requirements The US, the UK, and the Republic of Ireland Michele Seib, PE, CFM Neil Breton, Chartered Hydrologist

2. Overview Introduction Gathering & Analyzing Flood Data Mapping Flood Risk Using the Flood Data Conclusions

3. Overview Introduction Gathering & Analyzing Flood Data Mapping Flood Risk Using the Flood Data Conclusions

4. Introduction US Longest River 4,543 miles UK Longest River 220 miles Ireland Longest River 240 miles

5. Introduction US UK Ireland NFIP EU Directive 2007/60/EU

6. Overview Introduction Gathering & Analyzing Flood Data Mapping Flood Risk Using the Flood Data Conclusions

7. Gathering & Analyzing Flood Data Determining Drainage Areas US UKIreland Delineated for EACH study Use best available topography Drainage Areas pre-defined by catchment descriptors Standard Approach Datasets

8. Gathering & Analyzing Flood Data Hydrology US UKIreland Regression Gages Rainfall Runoff Other FEMA approved models FEH rainfall-runoff FEH Hydrographs IOH124 for urban locations Rational/Wallingford FSR FSU

9. Gathering & Analyzing Flood Data Hydraulics US UKIreland HEC-RAS 2-D Models Other FEMA approved models 1-D 2-D 1-D 2-D

10. Gathering & Analyzing Flood Data Structures

11. Overview Introduction Gathering & Analyzing Flood Data Mapping Flood Risk Using the Flood Data Conclusions

12. Mapping Flood Risk FIRM & FISSFRM & SFRACFRAM

13. Mapping Flood Risk FIRM & FIS

14. Mapping Flood Risk SFRM & SFRA

15. Mapping Flood Risk CFRAM

16. Overview Introduction Gathering & Analyzing Flood Data Mapping Flood Risk Using the Flood Data Conclusions

17. Using the Flood Data Mitigation Insurance Land Use Planning Development Flood Defense Structures

18. Overview Introduction Gathering & Analyzing Flood Data Mapping Flood Risk Using the Flood Data Conclusions

19. Combining different sources of risk assessment (such as in the UK) provides a holistic overview of all flood sources Revising entire maps/products (as in the US) provides a singular, definitive flood outline incorporating all changes and modifications Uncertainty maps highlight areas where flooding is still a risk for a particular event

20. Michele Seib Michele.seib@atkinsglobal.com Neil Breton Neil.breton@atkinsglobal.com