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.
The low-water flood of the Chagres river, just below the site of the proposed Gamboa Dam, is 209 feet wide by 7 feet 6 inches deep, the bed being triangular in cross section. In November 1885, a flood occurred here, under the influence of which the river was swollen to a width of 1560 feet, with a maximum depth of 28 feet, so that it was twelve times as wide as the canal and almost as deep at its deepest point. It is stated that the last four feet of the rise took place in four hours, and in thirty-six hours the water had risen about 20 feet. The general consensus of opinion among engineers appears to be that this immense flood has to be provided for in some way. M. de Lesseps originally proposed to meet the difficulty by constructing a dam, or embankment, two-thirds of a mile long, 1300 feet wide at the base, and 164 feet in height. This dam was to be designed so as to retain the floods which descend the Chagres river, storing the water and allowing it to escape gradually. The only alternative was to provide the flood waters with such a rapid means of escape to the ocean that they could not flood the canal.
From considerations of economy, it was recently determined to abandon the lock gates at the port of Panama. It was intended in the original scheme to provide these gates in order to control the rise and fall of the tide at this end of the canal. This movement of the tide varies from 20 to 27 feet, being at least twelve times as much as at the other end of the canal. Obviously, therefore, the canal would be seriously affected by a tidal movement of so considerable a character, and leading engineers have not hesitated to say that without the lock gates at Panama the canal is an impossibility.
American Views of the Enterprise.
“American engineers,” we are told, “have never had but one opinion of the canal. As a general thing they have never believed that it could be built on the lines, within the time, nor for the money specified by M. de Lesseps.” The same writer adds that “M. de Lesseps, having won fame by scooping out some sand hills and connecting some lakes and streams at Suez, thought it was a simple matter to make a canal anywhere. He has persistently refused to see any difficulties, or to squarely look the undertaking in the face, and to estimate the chances for and against its completion, and the collapse of all this will simply be a question of time.”[196]
Another American writer adopts much the same view, in even more emphatic language, when he says[197] that, “of the final cost of M. de Lesseps’s sea-level canal at Panama, if there could be anything about it save utter failure, nothing can be known, except that it will be a fabulous amount.... The great difficulties and expense of excavation are still before them, and the knotty, perhaps impossible, problem of the Chagres river is still unsolved.”
Further light on the difficulties in the way of the enterprise was thrown upon it in a report made by Lieut. Kemball, in 1887, to the United States Government. He found on the Pacific slope, a short distance west of the summit, that the route of the canal was here crossed and recrossed by the Rio Grande, which had been trained in a straight line down the north side of the valley, at a considerable height above the level of the canal.[198] It was found, however, when the rainy season had set in, that in different places the hillside began to slide into the cutting made for the deflection of the river, and that one bank moved almost intact across the cut, with the top surface unbroken, and without any disturbance of the vegetation. The existence of a substratum of a greasy clay bank was the cause of this trouble. Such a foundation is, of course, not to be relied on. It is ready, as has been pointed out, to “swell upwards, or glide sideways, on the slightest provocation, and it may easily develop into a difficulty of the most formidable character, requiring the river to be carried round the back of the hills away from the canal.”[199]
In the summer of 1887, Lieut. Rogers, of the United States Navy, visited the canal works, and made a report on them. He declared that in 1886, 11,727,000 cubic metres of excavation had been done, bringing the total quantity completed up to that date at 30 millions of cubic metres. This had, however, been done in the face of tremendous odds. An American dredger of greater power was steadily engaged on the same spot for weeks, the pressure of the material laid on the bank forcing up the soft spongy bed of the cut so rapidly that the machine could do little more than merely hold its own. The canal bed had here and there been destroyed by floods. Lines and trucks had been buried under two metres of silt. In the Culebra cut, the mountain to the left hand of the cut was found to be moving towards the canal, at the rate of 11 to 12 inches per annum. Seeing that this was the case when not one-third of the excavation had been completed, the query is naturally suggested, What will be the rate of movement when the bed of the canal is 250 feet or more under the level of the surrounding country?
