FLOOD-INUNDATION MAPS FOR THE YELLOW RIVER AT PLYMOUTH, INDIANA By Chad D. Menke, Aubrey R. Bunch, and Moon H. Kim U.S. Geological Survey Scientific Investigations Report 2016–5117 ABSTRACT: Digital flood-inundation maps for a 4.9 mile reach of the Yellow River at Plymouth, Indiana (Ind.), 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 05516500, Yellow River at Plymouth, Ind. Current conditions for estimating near-real-time areas of inundation using USGS streamgage information may be obtained on the Internet at http://waterdata.usgs.gov/in/nwis/uv?site_no=05516500. In addition, information has been provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service (AHPS) flood warning system (http:/water.weather.gov/ahps/). The NWS AHPS forecasts flood hydrographs at many sites that are often collocated with USGS streamgages, including the Yellow River at Plymouth, Ind. NWS AHPS-forecast peak-stage information may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation and forecasts of flood hydrographs at this site. For this study, flood profiles were computed for the Yellow River reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the current stage-discharge relations at the Yellow River streamgage, in combination with the flood-insurance study for Marshall County (issued in 2011). The calibrated hydraulic model was then used to determine eight water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The 1-percent annual exceedance probability flood (flood with recurrence intervals within 100 years) is between the calibrated water level stages for comparison. The simulated water-surface profiles were then used with a geographic information system (GIS) digital elevation model (DEM, derived from Light Detection and Ranging [lidar) in order to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage 05516500, Yellow River at Plymouth, Ind., and forecast stream stages from the NWS AHPS, provides 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. DISCLAIMERS: This report, identified as SIR 2016–5117, has been approved for release and publication by the Director of the U.S. Geological Survey. Although this report has been subjected to rigorous review and is substantially complete, the U.S. Geological Survey reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from its authorized or unauthorized use. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items for other than personal use must be secured from the copyright owner. Disclaimer for Flood-Inundation Maps: Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes. The USGS provides these maps “as is” for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information. Uncertainties and Limitations for Use of Flood-Inundation Maps: Although the flood-inundation maps represent the boundaries of inundated areas with a distinct line, some uncertainty is associated with these maps. The flood boundaries shown were estimated based on water stages (water-surface elevations) and streamflows at USGS streamgage 05516500. Water-surface elevations along the stream reach were estimated by steady-state hydraulic modeling, assuming unobstructed flow, and using discharges and hydrologic conditions anticipated at the USGS streamgage. The hydraulic model reflects the land-cover characteristics and any bridge or other hydraulicstructures existing as of March 2012. Unique meteorological factors (timing and distribution of precipitation) may cause actual discharges along the modeled reach to vary from those assumed during a flood and lead to deviations in the water-surface elevations and inundation boundaries shown. Additional areas may be flooded because of unanticipated conditions such as changes in the streambed elevation or roughness, backwater into tributaries along a main stem river, or backwater from localized debris or ice jams. The accuracy of the floodwater extent portrayed on these maps will vary with the accuracy of the digital elevation model used to simulate the land surface. If this series of flood-inundation maps will be used in conjunction with National Weather Service (NWS) river forecasts, the user should be aware of additional uncertainties that may be inherent or factored into NWS forecast procedures. The NWS uses forecast models to estimate the quantity and timing of water flowing through selected stream reaches in the United States. These forecast models (1) estimate the amount of runoff generated by precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds downstream, and (3) predict the flow and stage (and water-surface elevation) for the stream at a given location (Advanced Hydrologic Prediction Service [AHPS] forecast point) throughout the forecast period (every 6 hours and 3 to 5 days in the future in many locations). For more information on AHPS forecasts, please refer to http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf. CONTENTS: This report consists of a report and eight maps. The individual metadata files pertain to all of the maps and the shapefile. 00Readme.txt SIR2016–5117.pdf SIR2016–5117_dep_grd_metadata.met SIR2016–5117_shapefile_metadata.met Datafiles depth_grids.zip shapefile.zip The shapefile is as follows: shapefile.zip yelplymIN.shp (.dbf/.prj/.sbn/.sbx/.shp.xml/.shx) INSTRUCTIONS AND DOCUMENTATION FOR U.S. GEOLOGICAL SURVEY SCIENTIFIC INVESTIGATIONS REPORT 2016–5117 To access the data: The data files can be downloaded from http://dx.doi.org/10.3133/sir20165117. The main product is a Portable Document Format (.pdf) map and pamphlet that requires Adobe Acrobat for viewing. Acrobat software runs on a variety of systems and is available for download free of charge from Adobe at http://www.adobe.com. References to non-U.S. Department of the Interior (DOI) products do not constitute an endorsement by the DOI. By viewing the Google Maps application programming interface (API) on this Web site, the user agrees to these terms (terms found at http://code.google.com/apis/maps/terms.html) of service set forth by Google. Software preferred: Adobe Acrobat (6.x, 7.x, or 8.x), or Adobe Acrobat Pro (6.x, 7.x, or 8.x), or the free Adobe Reader (6.x, 7.x, or 8.x), 8.x is preferred. ArcGIS 10.2 preferred, older versions may also work. ArcReader may be downloaded free of charge from http://www.esri.com/software/arcgis/arcreader for viewing additional files included in this report.