 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 in modern times, conservation) difficulties, as this rock expands in the presence of water, forcing apart the stone surrounding it.