Countywide FEMA Floodplain Maps Effective November 26, 2010
*See bottom of page for Interactive Map of flood hazards*
Principal Flood Problems
The flood history of Columbia County indicates that there are two distinct periods of flooding: winter, when rainstorms cause usually rapid but short rises on the streams within Columbia County; and late spring, when snowmelt from the upper Columbia basin causes a slow but prolonged rise on the Columbia River along the northern and eastern boundaries of the county. During particularly severe winter storms, flooding usually occurs on many streams throughout the study area. Flooding is caused by heavy rainfall augmented by snowfall at a time when the soil is near saturation. default Read more...
(digital map replaces paper FIRM, dated 1992)
As part of the update, floodplain boundaries for McNulty Creek, Milton Creek and portions of the Columbia River were re floodplain boundaries for McNulty Creek, Milton Creek and portions of the Columbia River were redelineated using contour data provided by the City of St. Helens. The data consisted of topographic mapping with a vertical contour interval of two feet. The data were derived from aerial photography flown in 1995 and revised in 2001 for areas that experienced additional development.
As part of the update, floodplain boundaries were digitized from the effective FIRM panels. Aerial photography was used to adjust floodplain and floodway boundaries where appropriate.
Vernonia flooding, 1996
- 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.
- 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 KML -
Download Flood Insurance Study -
No plans at this time.
Snapshots around the county
None at this time
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)