Flood Inundation Depth for a Flow of 1,450 cfs (stage 12) at Gage 14211500, Johnson Creek near Sycamore, Oregon (sycor_12.tif)

The basis for these features is U.S. Geological Survey Scientific Investigation Report 2017-5024 Flood Inundation Mapping Data for Johnson Creek near Sycamore, Oregon. The domain of the HEC-RAS hydraulic model is a 12.9 mile reach of Johnson Creek from just upstream of SE 174th Avenue in Portland, Oregon to its confluence with the Willamette River. Some of the hydraulics used in the model were taken from Federal Emergency Management Agency, 2010, Flood Insurance Study, City of Portland, Oregon, Multnomah, Clackamas and Washington Counties, Volume 1 of 3, November 26, 2010. The Digital Elevation Model (DEM) utilized for the project was developed from LiDAR data flown in 2015 and provided by the Oregon Department of Geology and Mineral Industries. Bridge decks are generally removed from DEMs as standard practice. Therefore, these features may be shown as inundated when they are not. Judgement should be used when estimating the usefulness of a bridge during flood flow. Comparing the bridge to the surrounding ground can be more informative in this respect than simply looking at the bridge itself. Two model plans were used in the creation of the flood layers. The first is a stable model plan using unsteady flow in which the maximum streamflow is held in place for a long period of time (a number of days) in order to replicate a steady model using an unsteady plan. The stable model plan produced the areas of uncertainty contained in the sycor_breach.shp shapefile. The second is an unstable model plan that uses unsteady flow in which the full hydrograph (rising and falling limb) is represented based on the hydrograph shape of the December 2015 peak annual flood. The unstable model plan produced the flood extent polygons contained in the sycor.shp shapefile and the depth rasters and represents the best estimate of flood inundation for the given streamflow at U.S. Geological Survey streamgage 14211500.

Data and Resources

Field Value
accessLevel public
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datagov_dedupe_retained 20220721212438
identifier USGS:58f789b2e4b0b7ea5451f0d8
metadata_type geospatial
modified 20200827
old-spatial {"type": "Polygon", "coordinates": [[[-122.652, 45.443], [-122.652, 45.497], [ -122.475, 45.497], [ -122.475, 45.443], [-122.652, 45.443]]]}
publisher U.S. Geological Survey
publisher_hierarchy Department of the Interior > U.S. Geological Survey
resource-type Dataset
source_datajson_identifier true
source_hash 78bd0a1c7230ecb3341c79ecc44d3d5b30ad3f85
source_schema_version 1.1
spatial {"type": "Polygon", "coordinates": [[[-122.652, 45.443], [-122.652, 45.497], [ -122.475, 45.497], [ -122.475, 45.443], [-122.652, 45.443]]]}
theme {geospatial}
Groups
  • AmeriGEOSS
  • National Provider
  • North America
Tags
  • amerigeo
  • amerigeoss
  • ckan
  • digital-elevation-models
  • floods
  • geo
  • geoss
  • hydrology
  • inlandwaters
  • johnson-creek
  • national
  • north-america
  • portland-oregon
  • stream-discharge
  • streamflow
  • united-states
  • usgs-58f789b2e4b0b7ea5451f0d8
  • willamette-valley
isopen False
license_id notspecified
license_title License not specified
maintainer Adam J. Stonewall or Information Officer
maintainer_email info-or@usgs.gov
metadata_created 2025-11-21T23:07:05.896706
metadata_modified 2025-11-21T23:07:05.896710
notes The basis for these features is U.S. Geological Survey Scientific Investigation Report 2017-5024 Flood Inundation Mapping Data for Johnson Creek near Sycamore, Oregon. The domain of the HEC-RAS hydraulic model is a 12.9 mile reach of Johnson Creek from just upstream of SE 174th Avenue in Portland, Oregon to its confluence with the Willamette River. Some of the hydraulics used in the model were taken from Federal Emergency Management Agency, 2010, Flood Insurance Study, City of Portland, Oregon, Multnomah, Clackamas and Washington Counties, Volume 1 of 3, November 26, 2010. The Digital Elevation Model (DEM) utilized for the project was developed from LiDAR data flown in 2015 and provided by the Oregon Department of Geology and Mineral Industries. Bridge decks are generally removed from DEMs as standard practice. Therefore, these features may be shown as inundated when they are not. Judgement should be used when estimating the usefulness of a bridge during flood flow. Comparing the bridge to the surrounding ground can be more informative in this respect than simply looking at the bridge itself. Two model plans were used in the creation of the flood layers. The first is a stable model plan using unsteady flow in which the maximum streamflow is held in place for a long period of time (a number of days) in order to replicate a steady model using an unsteady plan. The stable model plan produced the areas of uncertainty contained in the sycor_breach.shp shapefile. The second is an unstable model plan that uses unsteady flow in which the full hydrograph (rising and falling limb) is represented based on the hydrograph shape of the December 2015 peak annual flood. The unstable model plan produced the flood extent polygons contained in the sycor.shp shapefile and the depth rasters and represents the best estimate of flood inundation for the given streamflow at U.S. Geological Survey streamgage 14211500.
num_resources 2
num_tags 18
title Flood Inundation Depth for a Flow of 1,450 cfs (stage 12) at Gage 14211500, Johnson Creek near Sycamore, Oregon (sycor_12.tif)