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.

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

[email protected]

Neil Breton

[email protected]