162 The Ohio Journal of Science [Vol. XVII, No. 5, 



The site selected was six miles above the city, at a place where 

 the valley walls were fairly close together, and above which the 

 valley widened a little. The dam was built on solid limestone 

 all the way across and set into limestone bluffs on each side. 

 Rock removed to build approaches and abutments was crushed 

 and used in the concrete construction. When completed, the 

 dam was high enough to pond the water back for fully four 

 miles or almost to the Dublin bridge. The mouths of little 

 tributary gorge valley's and several little quarries were drowned. 

 The old Dublin road had to be raised or reconstructed 50 to 100 

 feet higher up the bluffs. This improvement with a large filtra- 

 tion, softening, and pumping plant most admirably situated 

 near the junction of the two large rivers has put Columbus in 

 touch with one of the best water supplies to be found. 



Natural slopes toward the Scioto River from all parts of the 

 city, and the great gravel and sand beds south of the city for 

 settling tanks and filters have been taken advantage of in the 

 construction of a sewage system and disposal plant. 



Floods. — The young valleys of the Scioto and Olentangy 

 rivers with their considerable drainage basins above are subject 

 to floods of devastating dimensions. Nearly every spring a 

 moderate flood arrives at Columbus, and in years with excep- 

 tional combinations of circumstances the quantity of water 

 becomes alarming. The valleys above the city are rather steep 

 floored and at the city there is a decided decrease in the fall of 

 the stream with a widening of the valley. The unfortunate 

 condition is still further accentuated by several railroad grades 

 and wagon roads across the flood plain in the western part of 

 the city. These grades were built in part to keep the traffic up 

 and out of the water and in part to make easy grades for trains 

 getting in and out of the valley. They do not have enough 

 bridge section but are solid earth and stone walls nearly all the 

 distance across the valley and hence obstruct greatly the ready 

 egress of the water poured out upon the flats from the steeper 

 upper stream courses. 



The flood of 1913* proved the most destructive in the 

 history of the city, and made it very plain that measures should 

 speedily be taken to provide for this variable geographic 

 factor — the river flood stage. Among necessary improvements 



*Griggs, Julian, Engineering Xews, April, 1913. 



