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Scientific Investigations Report 2011–5189

Prepared in cooperation with the Village of Ottawa, Ohio, and the U.S. Department of Agriculture, Natural Resources Conservation Service

Development of a Flood-Warning Network and Flood-Inundation Mapping for the Blanchard River in Ottawa, Ohio

By Matthew T. Whitehead

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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.

Revised August 22, 2012

First posted November 16, 2011

For additional information contact:
Director, Ohio Water Science Center
6480 Doubletree Ave.
Columbus, OH 43229-1111

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Whitehead, M.T., 2011, Development of a flood-warning network and flood-inundation mapping for the Blanchard River in Ottawa, Ohio: U.S. Geological Survey Scientific Investigations Report 2011–5189, 8 p., 12 plates.


Installation and Upgrade of Streamgages
Hydrology and Hydraulics
Development of Flood-Inundation Maps
References Cited

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