Geomorphologic land classification map of Lake Kasumigaura, Kitaura and their vicinity, East of Tokyo

Abstract

We have made the geomorphologic land classification map of Lake Kasumigaura, Kitaura and their vicinity near Tokyo. The target area is classified by major geomorphological elements such as diluvial terraces alluvial terraces, valley plains natural levees, backswamps, former river courses, deltas, sand banks etc., utilizing the aerial photographs and field surveys. In preparing the sublacustrine map of the lakes, the bottom of the lakes are classified by major geomorphological elements such as littoral shelves, sublacustrine valleys, sublacustrine plains etc. utilizing the iso-depth line which made by the Geographical Survey Institute, Ministry of Construction and measurement with a Fathometer machine. These lakes are connected with the Pacific Ocean through the Tone River Valley. Therefore the geomorphology of the area is influenced by eustatic movement. There are Lacustrine Terrace I (4-8 m) and Lacustrine Terrace II (1.8-3 m). The former was formed in the maximum of Holocene Transgression Age i.e. between 6,000 and 4,000 years B.P. There are Littoral shelf I (- 1.0 to 1,5 m) and II ( -2.0 to -3,5m). About 2,100 or 2,000 years B.P. the sea water level was approximately – 3 m. We can use this map for the integrated development plan of water use and flood control. Furthermore, the map can be used for estimation of the site of soil liquefaction caused by earthquakes and for study of the geomorphologic development of the area.