- Published on Thursday, 07 July 2011 08:00
Countywide FEMA Floodplain Maps Effective March 17th, 2014
*See bottom of page for Interactive Map of flood hazards*
Principle Flood Problems
Most flooding in Coos County occurs on the Coquille River and its tributaries. The Coquille River at Coquille and the South Fork Coquille River at Myrtle Point typically exceed flood stage at least once each winter. Most other rivers and streams in the county flood less frequently. Riverine flooding usually occurs from November through February when storms moving inland off the Pacific Ocean cause heavy rainfall.
In the lower reaches of the Coquille River, higher than normal tides combining with high runoff can cause extensive flooding. Storm runoff is high because of moderately steep to steep terrain and the characteristic low soil permeability in the upper Coquille River valley. A natural constriction in the Coquille River valley downstream of Riverton and tidal influences control the flood elevations at the City of Coquille. The river valley at Coquille is flooded an average of 3 months each year. Natural levees along the riverbanks result in poor drainage from overbank areas as floodwaters recede. The worst flooding occurs when high tides combine with high runoff and onshore winds during major winter storms. Read more...
Map changes since previous release
Floodplain boundaries for portions of Pony Creek, Coos Bay, and the Pacific Ocean were revised with new topographic mapping. Pony Creek floodplain boundaries were revised within the corporate limit of North Bend using topographic mapping with a contour interval of 2 feet. Pony Creek is no longer protected by tide gates at Crowell Lane.
The Pony Creek floodplain area upstream of Crowell Lane was remapped using the 1-percentannual- chance still water elevations for Pony Slough to a point where the still water elevation equaled the Pony Creek flood profile elevation. Coos Bay floodplain boundaries were revised using topographic mapping with a contour interval of 2 feet. The topographic data included the entire City of North Bend and a portion of the City of Coos Bay. The topographic data extends along the bay shore within the City of Coos Bay from the northwest corporate limit of North Bend west for approximately 1,000 feet and, also extends south for approximately 1,200 feet from the southern corporate limit of North Bend.
Portions of the Pacific Ocean floodplain boundaries were revised using National Oceanic and Atmospheric Administration (NOAA) LIDAR data with a contour interval of 2 feet. The LIDAR data is "first return" and has not been post-processed to remove non-ground features. Therefore, only open ground areas were revised using the LIDAR contour data. Areas that were revised include the reaches from Coos Bay south jetty to Sunset Beach State Park and from the south jetty of the Coquille River to the mouth of Johnson Creek.
A "KML" is a file that can be downloaded and opened directly in Google Earth, ArcGIS Explorer and other viewing software available on the Internet. The KML below is for the Special Flood Hazard Area (SFHA), also known as the "100-year" flood.
- Download KML - click here
- A Flood Insurance Study (FIS) is the publication developed in conjunction with the Flood Insurance Rate Map (FIRM) and discusses the engineering methods used to develop the FIRMs. The study also contains flood profiles for studied flooding sources and can be used to determine Base Flood Elevations for some areas
- Download FIS (March 17, 2014) large file: click here
New Coos County FIRMs now effective (March 17, 2014)
Snapshots around the county
Note - For general information only - DO NOT use for regulatory purposes, especially for non-modernized areas: see "description" for source information and disclaimer
(hint: once in Viewer select "Basemap" in upper left corner for imagery background)