DEVELOPMENT OF A FLOOD WARNING NETWORK AND FLOOD-INUNDATION MAPPING FOR THE BLANCHARD RIVER IN OTTAWA, OHIO By Matthew T. Whitehead 2011 Scientific Investigations Report 2011-5189 ABSTRACT: Digital flood-inundation maps of the Blanchard River in Ottawa, Ohio, were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Department of Agriculture, Natural Resources Conservation Service and the Village of Ottawa, Ohio. The maps, which correspond to water levels (stages) at the USGS streamgage at Ottawa (USGS streamgage site number 04189260), were provided to the National Weather Service (NWS) for incorporation into a Web-based flood-warning Network that can be used in conjunction with NWS flood-forecast data to show areas of predicted flood inundation associated with forecasted flood-peak stages. Flood profiles were computed by means of a step-backwater model calibrated to recent field measurements of streamflow. The step-backwater model was then used to determine water-surface-elevation profiles for 12 flood stages with corresponding streamflows ranging from less than the 2-year and up to nearly the 500-year recurrence-interval flood. The computed flood profiles were used in combination with digital elevation data to delineate flood-inundation areas. Maps of the Village of Ottawa showing flood-inundation areas overlain on digital orthophotographs are presented for the selected floods. As part of this flood-warning network, the USGS upgraded one streamgage and added two new streamgages, one on the Blanchard River and one on Riley Creek, which is tributary to the Blanchard River. The streamgage sites were equipped with both satellite and telephone telemetry. The telephone telemetry provides dual functionality, allowing village officials and the public to monitor current stage conditions and enabling the streamgage to call village officials with automated warnings regarding flood stage and/or predetermined rates of stage increase. Data from the streamgages serve as a flood warning that emergency management personnel can use in conjunction with the flood-inundation maps by to determine a course of action when flooding is imminent. DISCLAIMERS: 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 contains copyrighted materials as noted in the text. Permission to reproduce copyrighted items for other than personal use must be secured from the copyright owner. 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. Purpose and Scope The purpose of this report is to describe methods and results of hydrologic and hydraulic analyses of the Blanchard River within the corporate limits of Ottawa, Ohio. A series of flood-inundation maps was developed for selected stages of the Blanchard River at Ottawa streamgage (04189260). Tasks specific to this study and discussed in this report were to (1) upgrade one existing streamgage and install two new streamgages, (2) install equipment enabling Ottawa officials to receive automated warnings about flood stage and/or predetermined rates of stage increase from the streamgages, and (3) estimate the areas of Ottawa that will be flooded at selected stages at the streamgage by developing flood-inundation maps. 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 which may be inherent or factored into NWS forecast procedures. The NWS uses river forecast models to estimate the quantity and timing of water flowing through selected river reaches in the United States. These forecast models (1) estimate the amount of runoff generated by a precipitation event, (2) compute how the water will move downstream, and (3) predict the flow and stage (water-surface elevation) for the river at a given location (AHPS forecast point) throughout the forecast period (every six hours over 3 to 5 days). For more information on AHPS forecasts, please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf A brief description of the contents: README.txt - this readme document depth_grids - subfolder containing 12 dpeth grids, one for each flood profile with file extensions: .aux/.rrd polygons - - subfolder containing 12 shapefiles, one for each flood profile with file extensions: .dbf/.prj/.sbn/.bsx/.shp/.shp.xml/.shx BR_Ottawa_OH.kmz - kmz file for all flood profiles with turn on/off capability using Google Earth software To access the data: The data files can be downloaded via the web from http://pubs.usgs.gov/sir/2011/5189/.The Report and Plates are in Portable Document Format (.pdf) which 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. To access the .kmz files in this report, download and install Google Earth at http;//www.google.com/earth/index.htm. Launch Google Earth, click the file menu and choose open. Locate and select the .kmz file on your computer. Software Required: 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 9.3 preferred, older versions may also work. Any questions regarding this report may be directed to: Matt Whitehead US Geological Survey, Ohio Water Science Center 6480 Doubletree Avenue Columbus, Ohio 43229 or via e-mail at mtwhiteh@usgs.gov