The long-term characteristics of bottom sedimentation and topography change in the estuary of Ishikari river

Abstract

Before Meiji Era, Ishikari river was nearly primitive river. Beginning development of Hokkaido, river basin development and improvement were carried out. And it was thought that sediment supplied from Ishikari river to river mouth was significantly changed in nearly 100 years. In this study, about 3m columnar cores were obtained in Ishikari bay, and 14c Measurement with Accelerator Mass Spectrometry and zinc content analysis were conducted. In the result, it turns out that the amount of sediment deposition increased more than 10 times in the past 90 years. Moreover, velocity of shoreline advance was estimated in nearly 100 years.