The City of Yankton is an active participant in the National Flood Insurance Program (NFIP) administered by the Federal Emergency Management Agency (FEMA). Participation in the NFIP is voluntary and is based on an agreement between the community and the federal government. If a community adopts and enforces a floodplain management ordinance to reduce flood risks, the federal government in turn makes flood insurance available within the community as a financial protection against flood losses.
On July 6, 2010, as part of FEMA’s Map Modernization Program, the City of Yankton enacted FEMA’s July 6, 2010 Digital Flood Insurance Rate Map (DFIRM) and Study. *The July 6, 2010 Digital Flood Insurance Maps replace the 1980 Flood Insurance Maps and Study.
Below is a summary of the differences between the 1980 Flood Insurance Rate Maps and the adopted July 6, 2010 Insurance Rate Map and Study.
- The 1988 North American Vertical Datum (NAVD) is used on the digital maps. This allows the use of the newer “bench marks” that are currently used by engineers, surveyors and the City of Yankton. The 1980 maps use the 1929 NAVD and many of these bench marks are no longer available. Many of the 1929 NAVD bench marks were placed on bridges and other features that have been destroyed, removed or replaced. The difference between the two datum is approximately .70 feet and this difference has been accounted for in the digital maps and associated flood insurance rate study.
- Definitions have been added or amended to the ordinance to meet the standards of the National Flood Insurance Program.
- The City boundaries have been changed on the digital map to reflect property that has been annexed into the city limits since the adoption of the 1980 Flood Insurance Rate Map.
- Areas that have been annexed are now shown on the Digital Flood Insurance Rate Map (DFIRM). Prior to this, these areas were shown on a Flood Boundary Hazard Map (FBHM). The DFIRM shows these areas in better resolution.
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