Brian M. Astifan | Geology Reports

USGS2009

Floods of August 21-24, 2007, in Northwestern and North-Central Ohio

Heavy rains in northwestern and north-central Ohio on August 19-22, 2007, caused severe flooding and widespread damages to residential, public, and commercial structures in the communities of Bluffton, Bucyrus, Carey, Columbus Grove, Crestline, Findlay, Mansfield, Ottawa, and Shelby. On August 27, 2007, the Federal Emergency Management Agency (FEMA) issued a notice of a Presidential declaration of a major disaster affecting Allen, Crawford, Hancock, Hardin, Putnam, Richland, Seneca, and Wyandot Counties as a result of the severe flooding. Rainfall totals for most of the flooded area were 3 to 5 in., with some locations reporting as much as 8 to 10 in. Three National Weather Service (NWS) gages in the area indicated a rainfall recurrence interval of greater than 1,000 years, and two indicated a recurrence interval between 500 and 1,000 years. Total damages are estimated at approximately $290 million, with 8,205 residences registering for financial assistance. The U.S. Geological Survey (USGS) computed flood recurrence intervals for peak streamflows at 22 streamgages and 8 ungaged sites in and around the area of major flooding. The peak streamflows at Sandusky River near Bucyrus streamgage and at seven of the eight ungaged sites had estimated recurrence intervals of greater than 500 years. The USGS located and surveyed 421 high-water marks and plotted high-water profiles for approximately 44.5 miles of streams throughout the nine communities.

Open-File Report↗

USGS2007

Flood of June 22-24, 2006, in North-Central Ohio, With Emphasis on the Cuyahoga River Near Independence

Heavy rains caused severe flooding on June 22-24, 2006, and damaged approximately 4,580 homes and 48 businesses in Cuyahoga County. Damage estimates in Cuyahoga County for the two days of flooding exceed $47 million; statewide damage estimates exceed $150 million. Six counties (Cuyahoga, Erie, Huron, Lucas, Sandusky, and Stark) in northeast Ohio were declared Federal disaster areas. One death, in Lorain County, was attributed to the flooding. The peak streamflow of 25,400 cubic feet per second and corresponding peak gage height of 23.29 feet were the highest recorded at the U.S. Geological Survey (USGS) streamflow-gaging station Cuyahoga River at Independence (04208000) since the gaging station began operation in 1922, exceeding the previous peak streamflow of 24,800 cubic feet per second that occurred on January 22, 1959. An indirect calculation of the peak streamflow was made by use of a step-backwater model because all roads leading to the gaging station were inundated during the flood and field crews could not reach the station to make a direct measurement. Because of a statistically significant and persistent positive trend in the annual-peak-streamflow time series for the Cuyahoga River at Independence, a method was developed and applied to detrend the annual-peak-streamflow time series prior to the traditional log-Pearson Type III flood-frequency analysis. Based on this analysis, the recurrence interval of the computed peak streamflow was estimated to be slightly less than 100 years. Peak-gage-height data, peak-streamflow data, and recurrence-interval estimates for the June 22-24, 2006, flood are tabulated for the Cuyahoga River at Independence and 10 other USGS gaging stations in north-central Ohio. Because flooding along the Cuyahoga River near Independence and Valley View was particularly severe, a study was done to document the peak water-surface profile during the flood from approximately 2 miles downstream from the USGS streamflow-gaging station at Independence to approximately 2 miles upstream from the gaging station. High-water marks were identified and flagged in the field. Third-order-accuracy surveys were used to determine elevations of the high-water marks, and the data were tabulated and plotted.

Scientific Investigations Report↗