My research work involved analyzing sediments from three coastal lakes in Japan to reconstruct history of past inundations. The sediments were collected from the lake bottom in the form of vertical cylindrical cores from the approximately the center of the lakes. Sediments collected from anywhere else would not be a stable archive of past inundations as they may get washed or shift with further inundations. Then the sediments were analyzed for grain size and content of organic and in organic materials on a layer by layer basis.