CHAPTER X. 

 RECENT CONSTRUCTION OF MOVABLE DAMS. 



In Bohemia. Probably the most interesting work of this character at the present 

 time is to be found in Bohemia, where a system of slackwater is being established 

 between Aussig, on the Bohemian Elbe, and Prague, on its tributary, the Moldau, a 

 distance of 190 miles.* When completed there will be thirteen locks, seven on the 

 Elbe and six on the Moldau, and twelve movable dams closed with needles only, or 

 with needles and Boute gates combined. The lift of the highest lock at Troja, just below 

 Prague, is given as 17.7 feet, and the smallest lift among the other locks will be 6.2 

 feet, the pool lengths varying from z\ to 8 miles. The total estimated cost of the 

 improvement is $4,320,000, or $22,800 per mile. 



These rivers have always formed the chief natural arteries for the commerce of 

 the kingdom, there being records of the existence of traffic upon them in the year A.D. 

 950. On the Elbe alone in 1822 there was a commerce of 19,700 tons, while in 1890 

 it had risen to more than three million tons. The usual processes of regularization 

 had been employed, but these gradually became insufficient to meet the demands of 

 traffic, and in 1892 it was recommended that a system of slackwater be established, 

 and, after the necessary surveys had been made, the project was finally approved by 

 the Government in December, 1895. The nvers flow through a hilly country and are 

 subject to sudden rises and to much ice, and as the valleys are thickly settled and manu- 

 facturing and agricultural interests very important, it was evident that only movable 

 dams would be suitable. 



The largest boats navigating the rivers are 230 feet long, 36 feet wide, and draw 

 6 feet on a burden of 700 tons. The minimum depth of water to be secured was there- 

 fore fixed at seven feet. 



The locks, wherever possible, will be placed in derivations, and will be all connected 

 by telephone or telegraph. 



The project also comprises the creation of two harbors of refuge for protecting craft 

 from floods or ice, and they will be capable of sheltering 180 large boats. Fishways are 

 to be provided at all dams. 



At the present time (1902) the first four dams, those of Troja, Klecan, Libschitz, 



* The information, together with the data for the drawings of certain details of construction, is obtained 

 from "La Canalisation de la Moldau et de 1'Elbc en Bohfime." V. Rubin, I'rajjuc, 1900. 



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