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Georges Creek Flood Study
Allegany County, Maryland
The purpose of this project is to prepare the hydrology and hydraulics and floodplain mapping for
Georges Creek, a major tributary to the North Branch Potomac River. The flood study was made for
Allegany County, Maryland. The study began at the confluence with North Branch Potomac River,
Westernport, Maryland, and it ended at a location 20 miles upstream of Midland. The Maryland
State Highway Administration Structure Hydrology and Hydraulics Unit and its Consultants worked jointly
with SAAD Consultants and FEMA Region III on this project. There was close coordination between Structure Hydrology and Hydraulics Unit, Allegany County, Maryland Department of Environment, and FEMA Region III.
Hydrologic analysis was performed. The peak flows were determined by performing frequency
analysis for Georges Creek gage at Franklin, using the USGS PEAKFQ program based on
Bulletin 17B. Rural discharges obtained from the regional regression equations were
adjusted for urbanization. The flow values of n-year at the gage were used to compute
the discharges at other un-gaged sites upstream and downstream of the gage. Hydraulic
modeling of the SAAD Consultants reaches was completed using HEC-2 and the SHA reaches
were completed using HEC-RAS. The entire reach was then combined using HEC-RAS model.
The interesting aspects of this study were bridge modeling and the split flow
downstream, passing Georges Creek toward the Potomac River, causing the flooding
of a large area of the City of Westernport not adjacent to Georges Creek.
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