PANAMA CANAL.

Manawatu Standard, Volume LIII, Issue 5, 3 December 1932, Page 7

PANAMA CANAL.

THE FLOOD PROBLEM. GATUN SMLLWAY GATES. When torrential rains flooded the Panama Canal and made jiecessary its closing to navigation (as was reported in the "Standard" on Wednesday) a fact long known to army engineers was again emphasised, and that is the striking similarity of conditions in the Canal Zone and in the Mississippi Valley. In both cases the flood problem is largely the result of excess saturation of the land, causing the waters to run wild and pile up "mountain high." With the volume of a dozen Niagaras they plunge into the Canal Basin, stopping navigation through the Canal, while slides in Gaillard Cut, which almost always come with the flood, add to the problems of the engineers on whose shoulders is placed the responsibility for the maintenance of traffic, wrote L. C. Speers in the New York Times after the. flood at the end of last year. ' 'The flood from which the Canal is now emerging, according to reports to the War Department, was about equal to the great flood of 1923, which disrupted navigation and was accompanied by a giant slide that completely cboked the channel and called into action every dredge and every available man in the Canal Zone," he wrote at that time. All this happened again and this time, as in 1923, the Canal force rose to the occasion. In less than two clays ships were again in transit between the two oceans. In the Canal sector the floods follow the wet seasons, just as those in the Mississipi Valley come with the heavy rains of the spring and the melting of the snows in the IJockies. At Panama the outlet is the Chagres River; in the United States the Mississippi, into which drain more than 90 -per cent, of all the rivers and creeks between the Alleghanies and the Rockies. When the saturation of the land is complete and escape through soakage is no longer possible, the Mississippi begins to put on her war paint. The same thing happens in the Canal Zone. DUE TO RAINS. The flood through which the Canal Zone has just passed was caused by torrential rains in the Gatun Lake watershed, which caused a rate of runoff into the lake equalled only by the run-off in 1923, when the discharge through the spillway gates and the culverts aggregated 175,000 cubic feet per second, while the storage in Gatun Lako increased not less than 6,000,000 cubic feet. Then, as now, the spillways and the culverts and the efficiency of the canal force saved the situation. In this last flood the Chagres River, through which the flood waters plunge into Gatun Lake, rose to almost re-cord-breaking heights. • Official information is that the Chagres reached an elevation at Alhajuela, the centre of the Madden Dam project, about equal to the 1923 rise, when the maximum elevation was 117.4 feet, or within 3.8 feet of the record of 1909. There were times in 1923 and again this year when, at the height of the flood, the water was entering Gatun Lake at approximately 300,000 cubic feet per second. Just as the Bonno Carre Spillway is to safeguard New Orleans from the menace of floods, so it is that a great spillway is the main defence of the Canal in time of flood. The Gatun Spillway, the backbone -of the Canal flood-fighting machine, is situated at about the centre of the Gatun Dam, It has fourteen gates or outlets and can, when the rise in tLo lake attains excessive heights, discharge the surplus waters at the rate of 200,000 cubic feet per second. As an additional safeguard there is a dyke below tho spillway on the east bank o.f the Chagres known as the Mindi Levee, which operates to prevent the spillage from escaping from tho river and entering the Canal through the old channel built by the French.

GATES OPENED. Eleven of the spillway gates were opened in 1923. The maximum discharge through thCso gates exceeded more than 150,000 cubic feet per second. What this means will be understood when it is stated that this discharge represents about one and onethird times as much water as is comtained in Gatun Lake when the elevations are between eight and eightyseven feet—which the engineers regard as the normal storage for the dry season reserve. In addition to tho spillway there are four side culverts in the walls of Gatun and Pedro Miguel locks which can take care, of about 36,000 cubic feet per second. The discharge through these culverts is about equal to the ma-jimum discharge of three spillway gates. In the opinion of most army engineers the Hood menace would have been many times greater than now is the case had a sea level instead of a lock canal been built.