Countywide FEMA Floodplain Maps Effective December 12, 2007
***See Interactive Map Tool at bottom of page***
Principal Flood Problems
There are three types of floods common to Willow Creek basin. One type of flooding occurs when a period of annual high water develops in early spring from melting snow, occasionally augmented by rainstorms. These flows seldom exceed channel capacities. A second type is caused by winter-rain snowmelt which usually occurs from December through February. It results from above average snowfall on frozen ground followed by warm rains. However, the most damaging floods in the basin are caused by violent summer thunderstorms with intense rainfall.
Floods of significant size occurred in 1885, 1888, 1891, 1903, 1904, 1917, 1918, 1961, 1965, 1971, 1979, 1983, and 1997. The May 1971 flood was caused by a thunderstorm at Heppner which resulted in a flash flood in Shobe Canyon. Its estimated peak discharge was 6,000 cubic feet per second (cfs), with an estimated recurrence interval exceeding the 0.2- percent-annual-chance flood. A very destructive flood occurred in June 1903. The storm centered in the headwaters area of Balm Fork and Willow Creek above Heppner and caused the death of 247 persons. It was estimated to have had a peak discharge of 36,000 cfs and a 0.28-percent annual chance flood above the confluence of Balm Fork and Willow Creek.
The rugged nature of the terrain and sparse vegetative cover of the watershed along with sudden occurrences of thunderstorms all combine to cause these destructive cloudburst floods.
Changes since last mapping
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 - default Morrow Co SFHA KML (4.01 MB)
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 County Flood Insurance Study: default Morrow Co FIS (920.32 kB)
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Snapshots around the County
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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)