Valley of the Kings rains. There is currently little year-round rain in this part of Egypt, but there are occasional flash floods that hit the valley, dumping tons of debris into the open tombs. The quality of the rock in the Valley is inconsistent, ranging from finely-grained to coarse stone, the latter with the potential to be structurally unsound. The occasional layer of shale also caused construction and conservation difficulties, as this rock expands in the presence of water, forcing apart the stone surrounding it. It is thought that some tombs were altered in shape and size depending on the types of rock the
Valley of the Kings that there are at least seven active flood stream beds leading down into the central area of the valley. This central area appears to have been flooded at the end of the Eighteenth Dynasty, with several tombs buried under metres of debris. The tombs KV63, KV62, and KV55 are dug into the actual wadi bedrock rather than the debris, showing that the level of the valley was five meters below its present level. After this event later dynasties leveled the floor of the valley, making the floods deposit their load further down the valley, and the buried tombs were forgotten