Germantown Dam


Germantown Dam is an earthen embankment located across Twin Creek in southwestern Montgomery County near the Village of Germantown. Conservancy Road goes across the top of the dam. Construction of the dam began in March of 1918 and was completed in November of 1920.  

The dam has two concrete conduits through the base of the embankment at the left (north) abutment. The conduits are sized to discharge floodwater at a rate that can be handled by the flood protection levees and channels downstream. The remainder of the floodwaters are temporarily stored behind the dam and released over time. An emergency spillway is located in a low area through the left abutment north of the dam. It would take eight days to empty the storage basin after a maximum high-water event. Germantown Dam can store 34.55 billion gallons of floodwater.


Germantown Dam Statistics

  • 1,210 feet long
  • 100 feet high
  • 655 feet wide at dam base
  • 865,000 cubic yards of earth in the embankment
  • Two conduits
  • Each conduit is 546 feet long, 9.1 feet high and 13 feet wide.
  • The spillway is 70 feet long.
  • Volume of concrete in the conduits is 16,300 cubic yards.
  • Drainage area above Germantown Dam is 275 square miles.


Elevation and Hydraulic Information 

  • Elevation of the dam is 830 feet above sea level.
  • Peak elevation Probable Maximum Flood is 826 feet above sea level.
  • Spillway elevation 815 feet above sea level.
  • Peak elevation Official Plan Flood (OPF) is 812 feet above sea level.
  • Elevation where storage begins is 736 feet above
    sea level
  • Peak discharge for OPF is 9,800 cubic feet per second.
  • Time to empty the storage area after an Official Plan Flood is eight days.
  • Water stored to the spillway would inundate 3,520 acres of land upstream from Germantown Dam. The 106,000 acre-feet of water would extend along Twin Creek 14 miles to Halderman Road, two miles south of West Alexandria in Preble County.


Directions to the Germantown Dam