Nebraska DNR s role in the making of FEMA s Digital Flood Insurance Rate Maps Becky Groshens (grow-hands) & Shelley Schindler
Important Terms: FIRM: Flood Insurance Rate Map FIS: Flood Insurance Study Non-Special Flood Hazard Areas: X,,0 0.2% %a annual chance flood hazard Typical Special Flood Hazard Areas or SFHA (areas that display the 100 year flood event): A, AE Floodplain: Any land area susceptible to a 100 year flood event. Floodway: the section of floodplain that contains the waterway in the event of a 100 year flood. BFE: Base Flood Elevation Cross sections: surveyed ground points along a line that shows the geometry of the floodplain and channel. Profile Baseline: the waterway in a detailed study.
Topics to Cover: What are FIRMs? History behind FIRMs Why do we need FIRMs? Why partner with FEMA? What goes into a DFIRM? What is DNR s role in this process?
Why do we need FIRMs? RichSmith_slate-FEMA_320x240.wmv http://www.flickriver.com/groups/740417@n25/pool/interesting/ http://www.newjerseypublicadjusters.net/ http://commons.wikimedia.org/wiki/file:fema_-_31793_- _FEMA_worker_looks_at_a_flood_damaged_home_in_Minnesota.jpg
Why Partner with FEMA? DNR and FEMA have common goals: Reduce loss of life Reduce loss of property Promote good floodplain management practices
How Floodplain Maps are Developed Base + Topography p + Flood Data = DFIRM Base Topography Flood Data DFIRM
Base Map 2009 or 2010(?) Farm Service Agency Aerials Corporate Limits Roads and Streets
Topographic Data LiDAR U.S. Geographical Survey topographical maps: Contours, 10m and 30m DEMs. Surveyed cross section elevation data.
Hydrology Flood Data Stream flows and discharges. Determine 100-year flood risk. 1% annual chance of flood risk Hydraulics Calculate water depths and water surface elevations.
Flood Data continued.. Generating a Floodplain Delineation Hydrology Hydraulics Water Surface Raster Floodplain Delineation USGS, Survey, or LiDAR Ground Information Ground Raster
Example of a Cross Sectional View
Detailed Study Example
Approximate Study Example
Data collected and checked: Base Map layers Political Boundaries City limits, ETJ s, Parks Public Land Survey data Transportation Features Flood Studies Detailed Studies Approximate Studies LOTS OF ANNOTATION!!
Bringing all that data together: QA/QC s DNR applies our own Topology check on base map features Example: self-overlaps, overlaps, self- intersections, dangles, gaps of polygons DNR follows strict protocol developed by FEMA to check SFHAs FEMA checks draft flood areas before final submission
Why is Nebraska DNR making FEMA DFIRMs?? DNR s Floodplain Management statutes state we are to assist local governments in implementation of effective floodplain management practices. DNR and FEMA have common goals. DNR has the most current data for Nebraska. Increases communication all levels. l FEMA sponsors local mapping projects.
Sample Timeline
Other DNR Mapping Projects Work maps for other counties Difference? BFE requests CNMS (Coordinated Needs Management Strategy) project Uses existing digital map data to inventory and manage flood map update issues
Recap DNR partners with FEMA to provide DFIRMs DNR utilizes GIS to create DFIRMs DNR performs QAs to check work FEMA checks DNRs work FEMA finishes post processing, prints, and distributes FIRMs
Thank You for Listening! Remember, Department of Natural Resources staff members are always available to answer your questions and support your needs. Please take our cards, and call us whenever you need help. Questions?
Information DNR Contact Rebecca Groshens Floodplain Mapping Specialist 402-471-12211221 rebecca.groshens@nebraska.gov gov Shelley Schindler Natural Resources Specialist shelley.schindler@nebraska.gov Bill Jones Floodplain Management Specialist 402-471-3932 bill.jones@nebraska.gov Andrew Christenson Floodplain Engineering Specialist 402-471-12231223 andrew.christenson@nebraska.gov Helpful Links FEMA Map Service Center www.msc.fema.gov National Flood Insurance Program www.floodsmart.gov Nebraska DNR Floodplain http://www.dnr.state.n e.us/floodplain/floodplai n.html