Flood Hazard Elevation Study Summary
(Click on the sheets to display the maps)
|SHEET NUMBER||NORTH-SOUTH STREETS INCLUDED|
|Sheet 1||Title Sheet|
|Sheets 2-4||Sheet Index|
|Sheets 5-7||20th St. to 17th St.|
|Sheets 8-11||17th St. to 13th St.|
|Sheets 12-13||13th St. to 11th St.|
|Sheets 14-17||11th St. to 9th St.|
|Sheets 18-20||9th St. to 8th St.|
|Sheets 21-25||8th St. to 7th St.|
|Sheets 26-29||7th St. to 6th St.|
|Sheets 30-32||6th St. to 5th St.|
|Sheets 33-35||5th St. to alley north of 5th St.|
This report gives property owners in central Concordia an estimate of whether they might be able to avoid or reduce flood insurance premiums. The Flood Hazard Elevation Study includes all the properties in the floodplain area between 20th Street and 5th Street along Broadway Street and Lincoln Street, and a portion of downtown 6th Street.
Aerial maps mark each of the 179 homes and commercial buildings in the area with a green, orange, or red box. Green means the property appears to be above floodplain level. Orange means the property appears to be not more than six inches below floodplain area. Red means the property appears to be more than six inches below the floodplain area. Approximately 12% of the mapped properties are marked green, 25% are marked orange, and 67% are marked red.
An application to the Federal Emergency Management Agency (FEMA) is required in order to remove a building from the floodplain. Owners of properties included in the study are encouraged to contact a surveyor for information as to the process, costs, and potential benefits of a FEMA application.
In March 2017, Campbell & Johnson, Engineers began an elevation study for the City of Concordia by acquiring surface ground elevations between the new 21st Street Dam and the 5th Street right of way. These field elevations were then analyzed in the office, using the approximate base flood elevations determined by the U.S. Dept. of Agriculture – Division of Water Resources. The following is a summary of that work.
The survey crew of Campbell & Johnson first established permanent benchmark elevations, connected to the North America Vertical Datum of 1988 and the Kansas State Plane Coordinate system, through the study area, using Global Positioning Satellite (GPS) surveying equipment. Most of these benchmarks were established on the top of existing city infrastructure such as manholes and fire hydrants.
These benchmarks provided a base control system for obtaining elevations beside the existing residential homes and commercial buildings, mapped to be inside the Special Flood Hazard Areas (SFHAs) subject to inundation by a 1% annual chance flood as determined by FEMA Flood Maps. A gravimetric survey level was then used in the acquisition of the field elevations near the structures. Campbell & Johnson also obtained additional elevations on other property and homes near the mapped flood areas that were structures of questionable floodable status.
Campbell & Johnson then compiled this information with aerial photography, a digital map of the boundaries of the SFHAs, and a map generated by the Division of Water Resources detailing the location and elevation of approximate base flood elevation (aBFE) contours. Using the compiled map, analysis was computed determining the approximate base flood elevation for each field obtained elevation location on the homes and buildings studied.
This information was then compiled into the following summary:
Approximately 225 homes and buildings were studied.
179 homes or commercial buildings were mapped within the 1% SFHAs.
The 179 homes were grouped into three categories in the 35 page study as shown by the placement of a green, orange or red box overlaid on the structure shown on the maps.
Green Box signifies that the field elevation indicated the structure was 1”-6” above the aBFE.
Orange Box signifies that the field elevation indicated the structure was 0”-6” below the aBFE.
Red Box signifies that the field elevation indicated the structure was 6” and greater below the aBFE.
GREEN BOX on structure
The Elevation Study determines that approximately 12% of all structures mapped in the SFHAs are above the mapped aBFE contour and with additional survey work may be applicable for removal from the SFHAs.
ORANGE BOX on structure
The Elevation Study determines that approximately 25% of all structures mapped in the SFHAs are just below the mapped aBFE contour and with additional survey work some of these structures may be applicable for removal from the SFHAs and if not removal then a reduction in Flood Insurance premiums.
RED BOX on structure
The Elevation Study determines that approximately 63% of all structures mapped in the SFHAs are over 6” below the mapped aBFE contour and are not likely to be removed from the SFHAs, but with further survey work may be eligible for a reduction in Flood insurance premiums.
A Certified Flood Plain Manager (City of Concordia – Bruno Rehbein) or a licensed land surveyor can explain the necessary documentation to apply for removal from SFHAs or to seek a reduction in flood insurance premiums.
Jason P. Johnson
Kenneth P. Johnson