The flood volume of the river Chagres has been estimated at 1600 metric tons of water per second, which is four times the volume of the highest flood ever measured on the Thames, and the rainfall, as a whole, has been known to exceed 120 inches in a single year. Besides all this, it was reported by M. de Lesseps himself,[195] that the borings on the Culebra range, had reached the depth of 100 feet without having met with rock. Some engineers have therefore condemned this part of the plans as faulty, arguing that such a cutting could not be expected to stand at a slope of one to one, even in a much drier climate—which means that the cutting through the Culebra would require to assume greatly larger dimensions, if it were to be of any value. One of the most serious undertakings connected with the Panama canal was the proposal to retain the flood waters of the Chagres, by means of the enormous embankment already referred to, between the Cerro Gamboa on the south, and the Cerro Barneo on the north, thus raising the level of the waters from 40 to 45 feet above the river, in order to allow of their escape. Other two projects were submitted to meet this difficulty—the first, that of constructing a canal for the flood waters of the Chagres alongside of the navigable canal; and the second, that of tapping the Chagres at Matachin, and diverting its waters to the Pacific. As regards the first of these two alternatives, it was objected that, as large affluents flow into the river below Matachin, three parallel canals of large size would require to be constructed, in order to make the alternative of any real value; the second alternative, it was held, would afford no relief to the floods of the Trinidad, the Gatun, and the smaller affluents of the Chagres below Matachin, while it would be likely to increase the difficulties of construction at the one end as much as it reduced them at the other. Nor is it admitted by some authorities that the Gamboa dam would be likely to answer its purpose. It is contended that many embankments would be required, instead of only one, and that the construction of such an embankment from such a cutting could hardly by any possible effort be completed in twenty-six years, so that it would not be until after that time had elapsed that the canal could be commenced between Chagres and Matachin, with its bed 30 feet under sea level.