Flood Mapping Across the Pond: A Comparison of Programs and Technical Requirements The US, the UK, and the Republic of IrelandMichele Seib, PE, CFMNeil Breton, Chartered Hydrologist
Overview• Introduction• Gathering & Analyzing Flood Data• Mapping Flood Risk• Using the Flood Data• Conclusions
Overview• Introduction• Gathering & Analyzing Flood Data• Mapping Flood Risk• Using the Flood Data• Conclusions
IntroductionUS
Longest River 4,543 miles
UK Longest River 220 miles
Ireland Longest River 240 miles
Introduction
US
UK
Ireland
NFIP
EU Directive 2007/60/EU
Overview• Introduction• Gathering & Analyzing Flood Data• Mapping Flood Risk• Using the Flood Data• Conclusions
Gathering & Analyzing Flood DataDetermining Drainage Areas
US UK Ireland
• Delineated for EACH study
• Use best available topography
• Drainage Areas pre-defined by catchment descriptors
• Standard Approach Datasets
Gathering & Analyzing Flood DataHydrology
US UK Ireland
• Regression• Gages• Rainfall Runoff• Other FEMA
approved models
• FEH rainfall-runoff• FEH Hydrographs• IOH124 for urban
locations• Rational/Wallingford
• FSR• FSU
Gathering & Analyzing Flood DataHydraulics
US UK Ireland
• HEC-RAS• 2-D Models• Other FEMA
approved models
• 1-D• 2-D
• 1-D• 2-D
Gathering & Analyzing Flood DataStructures
Overview• Introduction• Gathering & Analyzing Flood Data• Mapping Flood Risk• Using the Flood Data• Conclusions
Mapping Flood Risk
FIRM & FIS
SFRM & SFRA
CFRAM
Mapping Flood Risk
FIRM & FIS
Mapping Flood Risk
SFRM & SFRA
Mapping Flood Risk
CFRAM
Overview• Introduction• Gathering & Analyzing Flood Data• Mapping Flood Risk• Using the Flood Data• Conclusions
Using the Flood Data
Mitigation Insurance
Land Use Planning
Development
Flood Defense Structures
Overview• Introduction• Gathering & Analyzing Flood Data• Mapping Flood Risk• Using the Flood Data• Conclusions
Conclusions• 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
Michele Seib
Neil Breton
