Mr. Harts, 
358 DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 
In reporting on the improvement of the Ohio, in 1878, an engineer 
board commented as follows :* 
“The Board are decidedly of the opinion that there are but two 
possible ways of securing such a permanent depth of water in the 
Ohio River as its importance demands, the first of which is that 
advocated by the late Charles Ellet, a highly distinguished civil 
engineer, which proposed storing up the surplus water of floods in 
reservoirs near the head-waters of the tributary streams; and the 
second is the ordinary plan of slack-water, which has long been in 
use on the Monongahela and other rivers, and which was ably pre- 
sented by Mr. W. Milnor Roberts, formerly United States civil engineer 
in charge of the improvement of the Ohio River. 
“The first of these plans the board deem impracticable on account 
of the difficulty, if not impossibility, of finding locations for the neces- 
sary reservoirs, the immense cost of the system, its interference with 
the navigation of the tributaries on which the dams are located, its 
injury to agricultural, mining, and railroad interests in the valleys of 
these rivers, the difficulty of regulating the supply from the reservoirs, 
and the terrible effects that would be caused by accidents. 
“Mr. Ellet proposed dams 100 feet high, ponding back twenty-five 
miles of water. Should one such dam burst—and several such casual- 
ties are on record—all others below it would be sure to break, and a 
terrific flood would sweep down the river, destroying bridges, river- 
craft, houses, and thousands of human lives. For these reasons, which 
we do not think it necessary to elaborate, the board are decidedly of the 
opinion that the reservoir plan should be unqualifiedly rejected and 
that the slack-water system alone deserves investigation.” 
In France, as mentioned above, this subject was examined with a 
view to learning whether reservoirs actually diminished to any useful 
degree the danger of floods. The following is an abstractt of a paper 
by M. Gros, published in the Annales des Ponts et Chaussées, on 
“The Insufficiency of Reservoirs for Diminishing the Danger of 
Floods :” 
“The utility of reservoirs in diminishing damage from floods was 
taken into consideration, in France, after the inundations of 1856. 
Investigations were made in the valleys of the Seine, the Rhone, the 
Loire, the Garonne, and other important rivers, and resulted in the 
decision not to carry out the numerous reservoirs which had been pro- 
posed, owing to the uncertainty and doubtful efficacy of their action 
on floods. 
“Similar investigations were made on these rivers after the in- 
undations of 1875. These latter observations showed, in the case of 
the Garonne, that a reservoir capacity of 720 000 000 cubie yards would 
be required to protect Toulouse from a similar flood, and two or three 
times larger to protect Agen and the rest of the basin. The Saint- 
Ferréol reservoir, supplying the Canal du Midi, which has been cited 
as a specimen of the reservoirs that should be constructed, has only a 
capacity of under 8 000000 cubic yards, so that a very great number 
*Annual Report, Chief of Engineers, 1873, p. 541. 
fMinutes of Proceedings, Inst. C. E.. Vol. LXVI, p. 408. 
