Steadily, It was passed through the Dowlaishweram and Ráli under-sluices, but the apron behind the latter was only 25 feet wide, and on the l7th June it began to sink. The sluices were closed and an attempt was made to replace the apron; when suddenly the great head of water forced the sand from beneath the foundation of the sluices into the hollow formed by the sinking of the apron, and a portion of the sluices fell in. Seven out of fourteen piers collapsed; but fortunately the massive masonry formed a dam preventing any great rush of water and gave time for measures to be taken to check the extension of the damage.
In the working season of 1851 and the early part of 1852 these under-sluices were rebuilt and the finishing touches were put to the anicut and head-works. Their virtual completion may be considered to have been achieved by March 31st, 1852.
Large repairs and alterations in the dam have been carried out since its first construction. The constant additions to the rough-stone aprons have already been alluded to, and another important improvement has been the raising of the crest of the work. Even before it was finished in 1852, its height was found insufficient to secure an adequate supply of water to the canals at all seasons; and cast-iron grooved posts, fitted with horizontal planks to hold up when necessary an additional two feet of water, were fixed along its crest. This was still insufficient; and between 1862 and 1867 the masonry itself was raised two feet at a cost of nearly three lakhs, and the iron posts and planks were replaced on the top of the new work. In 1897-99 the crest was raised an additional nine inches with Portland cement concrete, and on this were fitted self-acting cast-iron shutters, two feet high, which fall automatically when the water rises to six inches above their tops.
The only serious accident to the anicut itself happened in 1857. On the 14th November of that year, when the season for floods was over and the water was comparatively low, the eastern end of the Maddúr branch suddenly subsided into a deep scour-hole below it, and a breach was formed through which the river poured with such depth and volume that it was impossible to stop it. The disaster was met by damming up the river (with great difficulty) some way above the anicut and then rebuilding the fallen portion. The operation cost half a lakh.
The three sets of head-locks, head-sluices and under-sluices, have all been altered or replaced at various times, and of the original constructions only one head-sluice and the three sets of under-sluices now survive. The original Vijésvaram head-lock was destroyed in the floods of 1852. It
