Hazus AAL Study

Update on Hazus AAL
Study and Data
Eric Berman - FEMA
Tom Schweitzer– STARR PTS
Tom Schweitzer
Dan Deegan
Shane Parson
Past Flood Risk Assessments:
Pre-HAZUS Studies
 Donnelly Data – mid 1980’s:
• Ranking of communities
• Use for decisions on mapping
 Property At Risk Data:
• Refinement of Donnelly
• Removed areas that would not
be developed (water bodies)
Average Annualized Loss (AAL)
 FEMA initiated the AAL Study in
2009 to provide a Nationwide
Loss Dataset
 Level 1 conducted on every
county in the contiguous United
States using Hazus-MH for both
Riverine and Coastal analysis
 Used national data sets for
consistency within the analysis
 Losses based on building and
Summary of Average Annualized
Loss (AAL) Study
 Hazus AAL Study
• Completed March 2010
• Used Hazus-MH MR4
• Losses for 48 states and the District of Columbia
• Included 3,109 counties
• Calculated losses for five return periods:
 10-year / 50-year / 100-year / 200-year / 500-year
• Calculated average annualized losses (AAL)
• AAL losses extracted from HPR files at the Census block
• AAL losses complied by county, state, and watershed (HUC-8, April 2010
• Usability analysis performed
Summary of AAL Study
 2009-10 Hazus-MH Flood Average Annualized Loss Estimation (AAL) was
performed for continental U.S.
 Level 1 Analysis
 Inputs:
• County-wide regions
• 10 sq mile drainage area
• Default Census data (GBS)
 Final Output included:
• Return period losses
• Total exposure
• Average Annualized Loss
• Annualized Loss Ratio
Relative Average Annualized Losses by State
AAL Results
 Total Annualized Losses Estimated at 55 Billion:
• Includes both riverine and coastal
Annualized Loss Ratio by State
Relative Average Annualized Losses by State
Using NFIP program average annual losses and other source of annual flood loss
data, sets a lower bound of the annualized flood loss at minimum of 10 billion
Hazus AAL Usability Analysis
Hazus AAL Usability Analysis (Performed by the 3 FEMA PTS)
• Completed 4/2011
• Analyzed several aspects of Hazus flood loss hazard
development and calculation and understand constraints
• Analyzed Hazus procedures to see if there are factors that
contributed to the high initial AAL loss number
• Can any of the procedures be quantified and used to adjust the
AAL loss totals?
• Developed an understanding of the limitations of a level 1
Hazus analysis (10 sqmi)
• Is the AAL data a usable data set for Risk MAP?
Hazus AAL Usability Analysis
• Use of 30 M DEM - some issues in developing an accurate
flood hazard, (only national topography data set)
• Use of the Census data is appropriate for this level of
analysis (planning level)
• The weighted area method for losses can overstate losses
• 10 sqmi drainage area - though limiting, use of smaller
threshold requires significantly more resources (processing
• Possible double counting of losses in coastal areas
Hazus AAL Usability Analysis
• AAL losses were overstated with 2 and 5 year return periods
losses included in the AAL calculation (removed from final
AAL estimate)
• AAL losses were recalculated outside of Hazus using the 5
return periods (10, 50, 100, 200, 500-year) losses
• AAL losses were calculated using Log normal*
• Should use only one cross-section for all return periods
• Data is appropriate for use in Discovery meetings,
sequencing and general comparison of relative risk between
* Hazus 2.1 uses a linear AAL calculation
Average Annualized Loss
 Availability Data & Format
• Shapefile format
• Access Database
• Data available by census block (2000 Census)
• Data available by watershed (HUC)
GIS Format
 Intended Uses:
• Identify flood prone areas and
• Communicate relative flood risk (building and content losses)
Use of AAL Values
Loss values need to be
shown as relative rather
than absolute dollar
Discovery Meeting
Discovery Map
Current AAL Data Availability
 Annualized Losses by Census Block (2000 Census)
1. Availability Data & Format
 Can be used to satisfy Discovery meeting requirements
Flood Risk Assessment
Purpose and Intended Uses
 Identify Areas and Communicate Relative Flood Risk:
• Flood prone areas
• Vulnerable people and property
 Provide Flood Risk $:
• Potential damage severity for different flood frequencies
• Identify locations with possible cost effective mitigation options
 Improve Estimates for Flood Risk $:
• Losses from Average Annualized Loss (AAL) Study
• Refined losses from new flood study depth grids
• Refined general building stock data from local sources
AAL Data Requirements –
Appendix O
Appendix O for Risk MAP
 Requires other data from the Hazus AAL data set
AAL Data Requirements –
Appendix O
AAL Access table only provides annualize loss data for:
Total Loss
Building Loss – Total
Contents Loss – Total
L_RA_AAL requires the following to be extracted from AAL
Study.HPR (Hazus) files:
Data for all 5 individual return periods
More detailed loss data fields (such as total, building, and
contents losses divided into residential, commercial, and
Flood Risk Data
AAL data has been compiled into a single database for use
in extracting the required data in Appendix O format
We have develop a tool that performs this extraction into
MS Access Databases
This is the initial assessment data that is required to
populate the Risk Database for use in producing Risk MAP
non-regulatory products
Flood Risk Data
Currently we are finalizing the data. It can be requested
from the PTS contractor for your Region.
Flood Risk Assessment Delivered
Flood Risk Map Elements
Flood Risk Report Elements
Moving Forward
The process for compiling the new data into a national data
sets has not yet been determined
Additionally the process to stored and distributed this data
nationally as yet been determined
Currently we are looking at storing the data associated with
Flood Risk Databases in the MIP until other means can be
developed to house the information.

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