Digital flood-inundation maps were created by the U.S. Geological Survey (USGS) in cooperation with the Muskingum Watershed Conservancy District and the City of Rittman as part of a Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS). The flood-inundation maps show estimates of the areal extent corresponding to the 1% and 0.2% annual-exceedance probability floods. Flood profiles were computed for each stream reach by means of a one-dimensional step-backwater model.

Digital flood-inundation maps were created by the U.S. Geological Survey (USGS) in cooperation with the Muskingum Watershed Conservancy District and the City of Rittman as part of a Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS). The flood-inundation maps show estimates of the areal extent corresponding to the 1% and 0.2% annual-exceedance probability floods. Flood profiles were computed for each stream reach by means of a one-dimensional step-backwater model.

Digital flood-inundation maps were created by the U.S. Geological Survey (USGS) in cooperation with the Muskingum Watershed Conservancy District and the City of Rittman as part of a Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS). The flood-inundation maps show estimates of the areal extent corresponding to the 1% and 0.2% annual-exceedance probability floods. Flood profiles were computed for each stream reach by means of a one-dimensional step-backwater model.

Digital flood-inundation maps were created by the U.S. Geological Survey (USGS) in cooperation with the Muskingum Watershed Conservancy District and the City of Rittman as part of a Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS). The flood-inundation maps show estimates of the areal extent corresponding to the 1% and 0.2% annual-exceedance probability floods. Flood profiles were computed for each stream reach by means of a one-dimensional step-backwater model.

Hydrologic and hydraulic analyses were done for selected reaches of the Grand River, Red Cedar River and Sycamore Creek near Lansing, Michigan. To update and expand a portion of the Federal Emergency Management Agency detailed Flood Insurance Study, the U.S. Geological Survey (USGS) and the City of Lansing initiated a cooperative study. The study comprised a 3.2-mile reach of the Grand River, a 30.2-mile reach of the Red Cedar River, and a 12.0-mile reach of Sycamore Creek. Historical streamflow data from multiple streamgages, Grand River at Lansing, MI. (USGS station number 04113000), Red Cedar River at East Lansing, MI. (USGS station number 04112500), Red Cedar River near Williamston, MI. (USGS station number 04111379), and Sycamore Creek at Holt Road near Holt, MI. (USGS station number 04112850) along with regional regression equations were used to estimate instantaneous peak streamflows for floods with 10-, 4-, 2-, 1-, 0.2-percent, and 1-percent plus annual exceedance probabilities. The 1-percent plus flood elevation is defined by the Federal Emergency Management Agency as a flood elevation derived by using streamflows that include the average predictive error for the regression equation streamflow calculation for the Flood Risk project. This error is then added to the 1-percent annual exceedance probability flood streamflow to calculate the 1-percent plus streamflow. The annual exceedance probability streamflows were then used in a Hydrologic Engineering Center-River Analysis System step-backwater model to determine water-surface elevation profiles and flood-inundation boundaries for the 10-, 4-, 2-, 1-, 0.2-percent, and 1-percent plus annual exceedance probability floods, and a regulatory floodway, along a selected reach of each stream. Each hydraulic model was calibrated to the current stage-streamflow relations at each streamgage. Flood-inundation boundaries for the 1- and 0.2-percent annual exceedance probability floods and a regulatory floodway were mapped for each stream.

Hydrologic and hydraulic analyses were done for selected reaches of the Grand River, Red Cedar River and Sycamore Creek near Lansing, Michigan. To update and expand a portion of the Federal Emergency Management Agency detailed Flood Insurance Study, the U.S. Geological Survey (USGS) and the City of Lansing initiated a cooperative study. The study comprised a 3.2-mile reach of the Grand River, a 30.2-mile reach of the Red Cedar River, and a 12.0-mile reach of Sycamore Creek. Historical streamflow data from multiple streamgages, Grand River at Lansing, MI. (USGS station number 04113000), Red Cedar River at East Lansing, MI. (USGS station number 04112500), Red Cedar River near Williamston, MI. (USGS station number 04111379), and Sycamore Creek at Holt Road near Holt, MI. (USGS station number 04112850) along with regional regression equations were used to estimate instantaneous peak streamflows for floods with 10-, 4-, 2-, 1-, 0.2-percent, and 1-percent plus annual exceedance probabilities. The 1-percent plus flood elevation is defined by the Federal Emergency Management Agency as a flood elevation derived by using streamflows that include the average predictive error for the regression equation streamflow calculation for the Flood Risk project. This error is then added to the 1-percent annual exceedance probability flood streamflow to calculate the 1-percent plus streamflow. The annual exceedance probability streamflows were then used in a Hydrologic Engineering Center-River Analysis System step-backwater model to determine water-surface elevation profiles and flood-inundation boundaries for the 10-, 4-, 2-, 1-, 0.2-percent, and 1-percent plus annual exceedance probability floods, and a regulatory floodway, along a selected reach of each stream. Each hydraulic model was calibrated to the current stage-streamflow relations at each streamgage. Flood-inundation boundaries for the 1- and 0.2-percent annual exceedance probability floods and a regulatory floodway were mapped for each stream.

Digital flood-inundation maps for a 6.6-mile reach of the St. Joseph River at Elkhart, Indiana were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at this site (NWS site EKMI3). Flood profiles were computed for the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind., reach by means of a one-dimensional step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current stage-discharge rating at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. The hydraulic model was then used to compute 6 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum ranging from 23.0 ft (the NWS “action stage”) to 28.0 ft, which is the highest stage interval of the current USGS stage-discharge rating curve and 1 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging [lidar]) data having a 0.49-ft root mean squared error and 4.9-ft horizontal resolution) to delineate the area flooded at each stage. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Digital flood-inundation maps for a 6.6-mile reach of the St. Joseph River at Elkhart, Indiana were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at this site (NWS site EKMI3). Flood profiles were computed for the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind., reach by means of a one-dimensional step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current stage-discharge rating at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. The hydraulic model was then used to compute 6 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum ranging from 23.0 ft (the NWS “action stage”) to 28.0 ft, which is the highest stage interval of the current USGS stage-discharge rating curve and 1 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging [lidar]) data having a 0.49-ft root mean squared error and 4.9-ft horizontal resolution) to delineate the area flooded at each stage. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Digital flood-inundation maps for a 6.6-mile reach of the St. Joseph River at Elkhart, Indiana were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at this site (NWS site EKMI3). Flood profiles were computed for the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind., reach by means of a one-dimensional step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current stage-discharge rating at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. The hydraulic model was then used to compute 6 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum ranging from 23.0 ft (the NWS “action stage”) to 28.0 ft, which is the highest stage interval of the current USGS stage-discharge rating curve and 1 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging [lidar]) data having a 0.49-ft root mean squared error and 4.9-ft horizontal resolution) to delineate the area flooded at each stage. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

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.