Documentation of Event Damages and Recurrence Intervals in the FEMA BCA Module

1. Documentation of Event Damages and Recurrence Intervals in the DFA ModuleFEMA BCA Webinar (Intermediate)Presenter: John Squerciati, DewberryApril 2012 (Modified for Residential Flood Mitigation Projects March 5, 2013) 1

2. Agenda Introduction Documenting Event Damages Documenting Event Recurrence Intervals (RIs) Documentation Dos and Don’ts Questions 2

3. 1. Introduction • This Introduction answers the following questions: • Why did my BCA fail? (i.e., did not meet FEMA requirements for cost-effectiveness) • What is a Damage Frequency Assessment (DFA) module and how do I use it? 3

4. Background: Why Did My BCA Fail? • All flood project BCAs need to determine flood risk to estimate project benefits. Higher flood risk means higher benefits, and vice versa. • Flood risk is based on flood recurrence intervals (RIs) and associated flood damages. • The FEMA BCAs submitted by your community used the Flood Module; which estimates flood risk for structures located in the FEMA floodplain as follows: • Flood RIs are based on the First Floor Elevation (FFE) of the structure relative to the Flood Insurance Study (FIS) profile data for the 10-, 50-, 100- and 500-year flood events • Associated flood damages are based on Depth Damage Functions (DDFs) associated with the project structure 4

5. Explanation: Why Did My BCA Fail? • The BCAs reviewed by Dewberry did not meet FEMA requirements because the project risk – and therefore the project benefit – was too low for the project to be cost-effective • The most common reasons why the project risk was too low: • The FFE was 2 feet or higher above the 10-year flood elevation • The FFE was above the BFE (100-year flood elevation) • The structure was located outside the SFHA (100-year floodplain) • The computed Benefit-Cost Ratio (BCR) was less than 1.0 5

6. What is a DFA Module? • The Damage-Frequency Assessment (DFA) module is a FEMA BCA approach which estimates flood risk for structures located in the FEMA floodplain or outside the floodplain: • Historic or expected flood damage event data • Recurrence Intervals (RIs) associated with the flood damage events 6

7. How Do I Use the DFA Module? • Input the Following Information into the DFA module: • Project Information • Event Damages • Event Ris • Note:FEMA BCAs prepared using the DFA module sometimes fail due to insufficient or incorrect documentation of event damages and RIs 7

8. Purpose and Target Audience • Purpose: Provide BCA users with FEMA-recommended examples and techniques to document damages and RIs for historic and expected events used in the DFA module. • Target Audience: IntermediateBCA Users - Preparers and Reviewers 8

9. 2. Documenting Event Damages • DFA Software Ground Rules – Two Types of Damage Events • For Historic Damages, need a minimum of two known RI events or three unknown RI events occurring in different years • For Expected Damages, need a minimum of two known RI events 9

10. Documenting Historic Damages • Historic Damage documentation sources: • Insurance Claims • Repair Records • News Articles citing credible sources 10

11. Insurance Claims – Flood Events • Useful for documenting historic damages to insured properties from various hazard events • For flood events, Subapplicants can obtain flood insurance claim data on all properties insured under the NFIP through BureauNet (http://bsa.nfipstat.com) • Additional benefits may be estimated from flood claims data when other event information is available. • Be aware of Severe Repetitive Loss (SRL) Program properties. 11

12. Repair Records • Useful for documenting historic damages to various facilities from hazard events • Repair records for residential buildings are typically limited to paid receipts for repairs or equipment rental • Repair records must: • be related to specific hazard events rather than scheduled maintenance or repairs, and • apply directly to structure(s) to be mitigated by the project • Always include complete copies of records organized in a spreadsheet when needed 12

13. News Articles Citing Credible Sources • News articles can include nationally or locally published newspapers or newsletters that are printed or posted online • Credible sources – sources other than homeowner accounts • Make sure the articles indicate the specific dates and impacts to structures to be mitigated by the proposed project 13

14. Documenting Expected Damages • Expected Damage documentation sources will vary based on the structure type and hazard to be mitigated • Building Damages tied to Flood Module Depth Damage Functions (DDFs) in FEMA BCA Software • Damages tied to Engineering Studies – Typically not done for residential building mitigation projects 14

15. Building Damages Tied to FEMA BCA Software • FEMA Flood Module Depth Damage Functions (DDFs) • Flood damages to buildings can be estimated using DDFs based on the structure information (building type, number of stories, foundation type, size and BRV) as a function of flood depth above the First Floor Elevation (FFE) • Documentation Sources • DDFs can be documented from the BCA software or transcribed into a separate document or spreadsheet (recommended) • Structure information can be documented from various sources, including tax records, structure plans with dimensions, site photographs, engineering reports, and building cost data • Be sure to establish the correct reference point for the FFE 15

16. 3. Documenting Event Recurrence Intervals (RIs) • DFA Software Ground Rules • For Historic Damage Events, need a minimum of two known RI events or three unknown RI events occurring in different years • For Expected Damage Events, need a minimum of two known RI events 16

17. Historic Damage Events – Known RI Approaches • Approaches Listed in General Order of Preference • Flood Elevations or Discharges tied to Identified Flood RIs • Determined by Hydrologist or Other Qualified Agency/Expert • Estimated using Climataological Data • Estimated Using Rain Gauge Data 17

18. Flood Elevations or Discharges tied to Identified Flood RIs • Documentation must include flood elevations and/or discharges from historic events as well as identified flood RIs that are used to determine the historic event RIs • Documentation Sources – Flood Elevations or Discharges • Both stream and tide gauge data can be obtained from the U.S. Geological Survey (USGS) website (http://waterdata.usgs.gov/nwis/sw) • Make sure the gauge data closest to the project structure(s) is used 18

19. Flood Elevations or Discharges tied to Identified Flood RIs (cont’d) • Documentation Sources – Identified Flood RI Data • The USGS PeakFQ Program; which can be downloaded from the USGS website (http://water.usgs.gov/software/PeakFQ). • Refer to Section 2.1.2 of the Supplement to the Benefit-Cost Analysis Reference Guide for step-by-step instructions and a detailed example of estimating RIs using this approach 19

20. Flood Elevations or Discharges tied to Identified Flood RIs (cont’d) • Documentation Sources – Identified Flood RI Data (cont’d) • FEMA Flood Insurance Study (FIS) Profiles and Discharge Tables or Transects; FIS data is available from the FEMA Map Service Center website (http://msc.fema.gov), then select Product Catalog from the top menu bar and search for the Effective FIS • When available, Hydraulics and Hydrology (H&H) Studies may be used where FIS data may be incomplete or out-of-date; must include complete copies of studies 20

21. Flood Elevations or Discharges tied to Identified Flood RIs - Examples 21

22. Determined by Hydrologist or Other Qualified Agency/Expert • Note that RI determinations may be limited for use in a specific geographic location, especially for large events such as Tropical Storm Allison (2001) or Hurricane Katrina (2005) • Documentation Sources • Post-event studies prepared by the U.S. Army Corps of Engineers (USACE) or the U.S. Geological Survey (USGS); must include complete copies of studies • Estimates prepared by a hydrologist; must include background data and/or calculations used to estimate RIs 22

23. Estimated Using Climatological Data • This approach is often useful for estimating RIs of weather-related events such as or severe thunderstorms or other storms • Be sure to include complete records of all events • Documentation Sources • The National Climactic Data Center (NCDC) provides data on various weather-related events by county and is available online (http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwEvent~Storms); note the range of available data and include details on individual events • Climatological data from State or local sources 23

24. Estimated Using Rain Gauge Data • Rain gauge data for historic damage events must be tied to flood RIs by a hydrologist or other qualified professional • Documentation Sources • The National Climactic Data Center (NCDC) records daily rainfall and other climactic data recorded by thousands of weather stations nationwide and is available online (http://www7.ncdc.noaa.gov/IPS/coop/coop.html); must include copies of all applicable data • NCDC also has Hourly Precipitation Data (HPS) data records available online (http://www7.ncdc.noaa.gov/IPS/hpd/hpd.html) • Analysis of rain gauge data prepared by a hydrologist; must include background data and/or calculations used to estimate flood RIs 24

25. Historic Damage Events – Unknown RI Approach Unknown Frequency Calculator - Requirements • Minimum of three hazard events occurring in different years where either: • The frequencies/RIs of all events are unknown, or • The frequencies/RIs of up to two events are knownand have total inflated values that exceed the total inflated values of all the other unknown frequency/RI events • Analysis Duration based on the age of the structure or a minimum of 10 years; whichever is greater • No other way to tie historical events to known RIs 25

26. Unknown Frequency Calculator • Documentation must include three historic event damages/losses and the date of construction for the structure to be mitigated • Documentation Sources • Historic hazard event damages/losses can be documented using approaches and sources listed previously for historic damage events • Date of construction can be documented using tax records, property appraisal, or included in a signed letter from a local official • NOTE: For multiple structures with different construction dates, the construction date of the oldest structure in the group must be used 26

27. Analysis Duration Adjustments • Analysis Duration is a key component of the Unknown Frequency Calculator, and can present difficulties for structure(s) that are older or where the date of construction is unknown • Adjustments to Analysis Duration • A User Input Analysis Duration may be allowed when one of the following situations apply • Change in Local Flow Conditions • Replacement of Structure • NOTE: No historic events may be included in the BCA that occur before the start of the adjusted Analysis Duration 27

28. Change in Local Flow Conditions • When local flow conditions have changed significantly over the life of a structure, it may be appropriate to adjust Analysis Duration • Documentation Sources • Documentation of change in local flow conditions may include: • Current and old FIS showing the before and after changes • Conditional Letter of Map Revision (CLOMR) or Letter of Map Revision (LOMR) • Hydraulics and hydrology (H&H) study that accounts for the change • Letter from city engineer or floodplain manager on community letterhead that addresses the changes in local flow conditions • Aerial photographs of the project area before and after the change in the watershed, or other photographs with dates showing increased development • Refer to Section 2.1.3 of the Supplement to the Benefit-Cost Analysis Reference Guide for step-by-step instructions and a detailed example of adjusting the Analysis Duration using this approach 28

29. Change in Local Flow Conditions -Examples BEFORE AFTER 29

30. Replacement of Structure • When a structure(s) to be mitigated are replaced or completely rebuilt, it may be appropriate to adjust Analysis Duration • Documentation Sources • Letter from a city engineer or building official on community letterhead with site photographs that includes the date and all details of the structure(s) replacement/rebuild • An engineering report with photographs that addresses the date and all details of the structure(s) replacement/rebuild • Current and old tax records with photographs that indicate the replacement of the structure(s) • NOTE: Partial rebuilding/replacement of a structure(s) is not acceptable documentation to adjust the Analysis Duration 30

31. Historic Damage Events – Summary of Unknown RI Approach • Important Things to Remember About the Unknown Frequency Calculator… • This was intended to be a “last resort” approach • It is less likely to yield cost effective results for three historic damage events as the analysis duration increases (typically beyond 30 years) 31

32. Expected Damage Events – Known RI Approaches Only • Estimated Event RIs based on Flood Module RIs in FEMA BCA Software • Estimated Event RIs from Engineering Studies – Typically not done for residential building mitigation projects 32

33. Estimated Event RIs based on Flood Module RIs in FEMA BCA Softwaree • Flood Event RIs from Flood Module • Flood Event RIs are estimated in the Flood Module as a function of flood depth based on FEMA Flood Insurance Study (FIS) or equivalent Hydraulics and Hydrology (H&H) data • Documentation Sources • FIS Profiles and Discharge Tables or Transect data is available from the FEMA Map Service Center website (http://msc.fema.gov), then select Product Catalog from the top menu bar and search for the Effective FIS • When available, H&H Studies may be used where FIS data may be incomplete or out-of-date; must include complete copies of studies 33

34. 4. Documentation Dos and Don’ts • Documentation DOs • DO provide all necessary supporting documentation for event damages, losses and RIs • DO provide complete copies of H&H studies and engineering studies • DO use FEMA Data Documentation Templates to organize documentation 34

35. Documentation Dos and Don’ts (cont’d) • Documentation DON’Ts • DON’T assume the reviewer can access documentation online • DON’T forget to include an explanation of any assumptions made • DON’T use unreliable or non-credible documentation sources 35

36. 5. Questions FEMA BCA Website • http://www.fema.gov/government/grant/bca.shtm FEMA BC Helpline Phone: 1-855-540-6744 E-mail:bchelpline@dhs.gov 36