550 THE PANAMA ROUTE FOR A SHIP CANAL. 



of fact, the total channel section in that year was less than it is at the 

 present time. Hence, if it be assumed that a Hood of 140,000 cubic 

 feet per second must be controlled, an error on the safe side will be 

 committed. Other g-reat floods of which there are reliable records are 

 as follows: 



The maximum measured rate of the 1890 flood was 74,998 cubic feet 

 per second, and that of 1893, 48,975 cubic feet per second. It is clear, 

 therefore, that a flood flow of 75,000 cubic feet per second is very rare, 

 and that a flood of 140,000 cubic feet per second exceeds that of which 

 we have any record for practically forty years. 



It is obvious that the dam, as designed by the Commission, is of such 

 character that no water must be permitted to flow over its crest or even 

 in immediate proximity to the downstream embankment. Indeed, it 

 is not intended by the Commission that there shall be any wasteway or 

 discharge anywhere near the dam. At a point about 3 miles southwest 

 of the site of the dam at Bohio is a low saddle or notch in the hills, 

 near the headwaters of a small stream called the Gigante River. The 

 elevation of this saddle or notch is such that a solid masonry weir, with 

 a crest 2,000 feet long, iiuw readily be constructed with its foundations 

 on bed rock without deep excavation. This structure is called the 

 Gigante spillway, and all surplus flood waters from the Chagres would 

 flow over it. The waters discharged would flow down to and through 

 some large marshes, one called Peiia Blanca and another Agua Clara, 

 before rejoining the Chagres. Inasmuch as the canal line runs just 

 easterly of those marshes, it would be necessary to protect it with the 

 levees or embankments to which allusion has already been made. 

 These embankments are neither much extended nor very costl}^ for 

 such a project. The })rotection of the canal would be further aided 

 b}^ a short artificial chiuinel between the two marshes, Pefia Rlanca and 

 Agua Clara, for which })rovision is made in the estimates of the Com- 

 mission. After the surplus waters from the Gigante spillway pass 

 th(\se marshes they again enter the Chagres River or How over the 

 low, half-su})merged country along its borders, and thence through its 

 mouth to the sea near the town of Chagres, about ti miles northwest 

 of (Jatun. 



The masonry crest of the(iigant(^ spillway would be [)laced at an 

 elevation of 85 feet above the sea. identically the same as that which 

 ma}^ be called the normal sununit level of the canal. It is estimated 



