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One-Percent Annual Flood Hazard and Exposure Risk Maps, Coos County, Oregon, by Mathew A. Tilman.
FEMA (Federal Emergency Management Agency) produces flood maps that show areas that have a 1 in 100
chance of being flooded in any year (the 100-year flood). These maps are made by using the historical record of
flood height and frequency, a hydrologic computer model, and the best available topographic data. The resulting
maps, called DFIRMs (Digital Flood Insurance Rate Maps), are used to determine which properties need flood
The Oregon Department of Geology and Mineral Industries (DOGAMI) has updated the DFIRMs for Coos
County, Oregon by using new, extremely accurate topographic data collected with a laser scanning system
called lidar (light detection and ranging). The new DFIRMs much more accurately show flood zone boundaries
and also allow us to measure flood depth at any point. At the same time, lidar data allow us to locate every
building in a community and make a GIS (geographic information systems) map that shows the exact location,
elevation, zoning class, and assessed value of each building collected from tax assessor records. Together, these
new types of information can provide a very detailed map that shows the general level of flood risk exposure for
each building in a community.
This information can be used by city officials, emergency managers, property owners, lenders, and insurers to
better understand flood risk and reduce risk from future floods.
UNDERSTANDING THE MAPS
The maps show areas expected to be flooded during a 100-year flood. The expected depth of flooding is shown by
one of three colors:
Buildings are color coded to show exposure to flood risk. Note that this color scheme is based on the assumption
that all buildings are constructed with slab-on-grade foundations; that is, the color codes are for the worst case
scenario (see Figure 1).
|Open-File Report O-10-05||One-Percent Annual Flood Hazard and Exposure Risk Map, City of Bandon, Coos County, Oregon||1:6,000|
|Open-File Report O-10-06||One-Percent Annual Flood Hazard and Exposure Risk Map, City of Coos Bay, Coos County, Oregon||1:12,000|
|Open-File Report O-10-07||One-Percent Annual Flood Hazard and Exposure Risk Map, City of Coquille, Coos County, Oregon||1:6,000|
|Open-File Report O-10-08||One-Percent Annual Flood Hazard and Exposure Risk Map, City of Lakeside, Coos County, Oregon||1:6,000|
|Open-File Report O-10-09||One-Percent Annual Flood Hazard and Exposure Risk Map, City of Myrtle Point, Coos County, Oregon||1:6,000|
|Open-File Report O-10-10||One-Percent Annual Flood Hazard and Exposure Risk Map, City of North Bend, Coos County, Oregon||1:6,000|
|Open-File Report O-10-11||One-Percent Annual Flood Hazard and Exposure Risk Map, City of Powers, Coos County, Oregon||1:6,000|
Each publication CD-ROM includes:
Also see companion publications FEMA Flood Zone Change Maps, Coos County, Oregon and the Oregon HazVu Web Tool.
O-10-05, Bandon, actual size 36 x 52 inches:
O-10-06, Coos Bay, actual size 48 x 36 inches:
O-10-07, Coquille, actual size 36 x 41 inches:
O-10-08, Lakeside, actual size 36 x 44 inches:
O-10-09, Myrtle Point, actual size 36 x 44 inches:
O-10-10, North Bend, actual size 36 x 46 inches:
O-10-11, Powers, actual size 30 x 35 inches: