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Lessons Learned: Risk MAP Early Demonstration Project Madison County, AL . TN AFPM 2011 Montgomery Bell State Park July 28, 2011 Eric Zgonina , EIT AMEC . Map Modernization & Risk MAP Overview Risk MAP Early Demonstration Purpose Study Area Selection/Proposal

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lessons learned risk map early demonstration project madison county al

Lessons Learned: Risk MAP Early Demonstration Project Madison County, AL

TN AFPM 2011

Montgomery Bell State Park

July 28, 2011

Eric Zgonina, EIT


presentation outline
Map Modernization & Risk MAP Overview

Risk MAP Early Demonstration Purpose

Study Area Selection/Proposal

Product Results and Findings

Stakeholder Feedback

Mapping Partner Recommendations

Moving forward with Risk MAP

Presentation Outline
fema map modernization program
FEMA Map Modernization Program
  • Map Mod brought NFIP mapping into 21st century
  • Ran from 2003-2010
  • Transition from paper to digital format
    • Significant advantages in capability and precision
  • New digital SFHA’s for 92% of the population
  • Encourage use of quality local data
fema vision for risk map
FEMA Vision for Risk MAP
  • FEMA Risk Mapping, Assessment, and Planning (MAP) Program
    • Deliver quality flood data that increases public awareness
    • Initiate mitigation measures to reduce risk and loss of life and property
    • Transform traditional flood mapping to better integrate:
      • Identification
      • Assessment
      • Communication
      • Planning for
      • Mitigation of flood related risks
  • Ensure 80% of the Nation’s flood hazards are current
  • Update flood hazard data for 100% of the populated coastal areas in the Nation
risk map early demonstration purpose
Risk MAP Early Demonstration Purpose

Risk MAP Development

  • Early Demonstration Projects
    • Validate Risk MAP products increase value to program vision
    • Emphasize production efficiencies and innovations
    • Update Guidance
    • Ascertain product refinement
    • Determine costs
    • Stakeholder feedback
early demonstration requirements
Early Demonstration Requirements

Project study area funded prior to 2010, pre-appeal phase

Strong Regional Support

Efforts could not exceed $100k

Good elevation data

Completion by February 2011, lessons learned integrated prior to FY2011 Risk MAP

early demonstration area selection madison county al
Early Demonstration Area Selection, Madison County, AL
  • Produce:
    • Changes Since Last FIRM
    • Flood Risk Probability Grids
    • Depth Grids
    • Flood Risk Report
    • Flood Risk Map
    • Two Stakeholder Meetings
  • Enhanced:
    • Annualized Loss Estimates
    • Velocity Grids
    • Areas of Mitigation Interest

Madison County Project

Effective 1998

FY2008/2009 funding

Strong stakeholder relationship, OWR and AMEC

Current ground surface data:LiDAR 2007

Area which will benefit from products, mitigation potential

Existing county revision, several detailed studies

changes since last firm
Changes Since Last FIRM

CSLF example: Bradford Creek, Madison, AL

  • ESRI model builder tool developed
  • Data stored in Flood Risk Database
  • FRR shows summaries SFHAs affected
  • Greatest level of effort:
    • attributing factors contributing to the shape of the SFHA
    • Population and buildings affected
areas of mitigation interest
Areas of Mitigation Interest

Channel Improvements

areas of mitigation interest1
Areas of Mitigation Interest

Flood Control Structures

water surface elevation and flood depth grid
Water Surface Elevation and Flood Depth Grid

Initial Raster Mosaicing

  • By products of floodplain mapping
  • Mosaicingrasters can horizontally skew data
  • Resampling model grids can reduce the magnitude of the skew
    • Resulted in average horizontal skew of less than one foot
velocity grid methodologies
Velocity Grid Methodologies


Using AFG Floodplain

Using Geo-RAS Floodplain

  • HEC-GeoRAS and RAS Mapper methodologies were considered
  • HEC-GeoRAS - smoothest and most accurate velocity grid
    • Floodplain polygons required inputs for velocity grid creation
    • AFG chosen over HEC-GeoRAS
velocity grid results
Velocity Grid Results

Velocity grid example: confluence of Indian Creek Trib 1 and Indian Creek, Intersection of Slaughter Road and Interstate 565 Huntsville, AL, 100 yr event

percent chance of flooding equations
Percent Chance of Flooding Equations

30 -Year Percent Chance

1 - (1 - p)30

percent chance of flooding methodology
Percent Chance of Flooding Methodology

Procedure derived based on FEMA guidance

ESRI model builder tool created

Grids were created for each of the selected flooding source intervals and mosaiced by county

percent annual chance and percent 30 year results
Percent Annual Chance and Percent 30-Year Results

Aldridge Creek, near Valley Hill Country Club area, Huntsville, AL

flood risk assessment
Flood Risk Assessment
    • Flood Risk Assessment Products (10%, 4%, 2%, 1%, 0.2%, and annual chance)
  • Area (Risk, Very Low to Very High)
  • Classification (Residential, Commercial, Other)
  • Population
  • Average Value (buildings/census block)
  • Total Loss
  • Building Loss
  • Content Loss
result discrepancies
Result Discrepancies

High density in floodplain, LOW RISK?

Undeveloped areas,

high risk?

locally supplied building data
Locally Supplied Building Data

Content value

Building type


Occupancy class

  • Building footprints
  • First floor elevations
  • Constructions materials
  • Number of stories or height
  • Year built/age/building quality
  • Building value
flood risk assessment results
Flood Risk Assessment Results

FEMA provided a Level 1 HAZUS risk assessment for each census block.

Results were poor in quality.

Classified all census blocks as residential in Madison County.

Community stakeholders noted areas of high risk labeled as very low risk in HAZUS.

Enhanced flood risk assessment not possible with current version of HAZUS, needs to be revised.

watershed flood risk report
Watershed Flood Risk Report
  • Provides a summary of all flood risk information in single source.
flood risk map
Flood Risk Map
  • Countywide base data
  • Contributing Engineering Factors
  • Areas of Mitigation Interest
revised fema guidance appendix n o
Revised FEMA Guidance, Appendix N & O


  • Contributing engineering factor became a variable attributed with 12 possible fields
  • Ex: New Terrain Data- If new terrain data was introduced and that new data caused the floodplain boundaries to change, the attribute would be “True”
  • No procedure for start/end of flooding sources included.
  • No new field for new flood source added
revised fema guidance appendix n o1
Revised FEMA Guidance, Appendix N & O

Flood Depth Analysis Grids

  • Defined naming convention and raster cell size (resolution) for all raster datasets =10 meters (32.808 feet).
  • If higher resolution depth or analysis rasters are produced, Mapping Partners shall submit outside of the FRD.
  • Section detailing combining depth grids at a confluence, acceptable depth difference (+/- 0.5 ft), engineering judgment applied when exceeds
revised fema guidance appendix n o2
Revised FEMA Guidance, Appendix N & O

Flood Risk Assessment

Guidance details MR4 version cannot calculate annualized loss but does include a HAZUS alternative loss calculation formula.

Guidance does not address partial dataset information entered into the Comprehensive Data Management System (CDMS) but defers users to CDMS manual.

MR5 available and new version of CDMS should be available soon


Remains point feature

Defines how to create AOMI Data including detailing the data mining process

revised fema guidance appendix n o3
Revised FEMA Guidance, Appendix N & O


Guidelines are not mandatory and some portions may be tailored by writer

Template Tables may be edited based on available information

Template text edited


Purpose of FRM is intended for facilitation purposes to involve communities

Legend modified- specifies AOMIs

Most recommendations followed

mutually beneficial partnerships
Mutually Beneficial Partnerships

Develop a framework that collects information on the effectiveness of partnerships

Ensure Risk MAP products from partnerships are complementary and not duplicative

Collaborate with partners to improve understanding and encourage action

Provide support to partners to include policies, procedures, guidelines, and training

outreach and communications1
Outreach and Communications

Reaching Stakeholders

  • Conferences
  • Media Relations
  • Community Meetings
  • Social Media
    • Facebook
    • Twitter
  • Web Applications
    • Phone apps
  • Other
presentation conclusions
Presentation Conclusions
  • Risk MAP Early Demonstration Project was successful
    • Emphasized production efficiencies and innovations
    • Presented product cost estimates
    • Provided Stakeholder feedback
    • Provided Mapping Partner feedback
    • Aided in update to guidance