Floodplains & Models

Looking for reference information about flooding?

Clean Water Services has worked with the Federal Emergency Management Services and Washington County to conduct a re-study of the floodplain in Washington County. The models referenced here represent the best available information on the floodplain's location, water surface elevation, and cubic feet per second of peak stream flows, and are currently undergoing an approval process through FEMA. Until the models are accepted by FEMA, they are not final, but remain the best available information.

This data was created for the floodplain update project and was submitted to FEMA on 3-3-06. While these maps may help developers and others locate floodplains, they are not to be used to determine whether property owners need flood insurance. Only FEMA has that information at www.fema.gov. FEMA also has floodplain data on areas outside the Urban Growth Boundary.

The models are developed for use by engineers and can be viewed by obtaining free software, HEC-RAS or HEC-HMS, from the US Army Corps of Engineers. Others may wish to view maps or obtain GIS data and may do so by viewing the Watershed Data Catalog and clicking on 100-Year Floodplain, or Cross Sections with Water Surface Elevations.

Hydrology & Hydraulics Models contain projected 2, 5, 10, 25, 50,100, & 500 year flows.

Stream or Area Name Hydraulics
(HEC-RAS Models)

Existing & Future Hydrology
(HEC-HMS Models)

Future Hydrology
(HEC-HMS Models)
Allen Allen
Beal Beal
Beaverton Beaverton East
Bethany Bethany East
Bronson Bronson East
Butternut Butternut East
Cedar Cedar Cedar Cedar
Cedar Mill - North Johnson Cedar Mill - North Johnson CM Update
Celebrity Celebrity East
Chicken Chicken Chicken Chicken
Council Council Dairy
Dairy Dairy Dairy
Dawson Dawson East
Deer Deer
Erickson Erickson East
Fanno Fanno Fanno
Gales Gales
Glencoe Glencoe
Gordon Gordon
Hall Hall East
Hedges Hedges Hedges Hedges
Holcomb Holcomb East
Johnson South Johnson South East
Lake Oswego Lake Oswego
McKay McKay Dairy
Nyberg Nyberg Nyberg Nyberg
Rock Rock East
Rock South Rock South Rock South Rock South
Storey Storey Dairy
Tualatin Lower Tualatin Lower
Tualatin Upper Tualatin Upper
Turner Turner East
Waible Waible Dairy
Willow Willow East

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