Author(s)

H. Gotoh, M. Takezawa, Y. Maeno, H. Oshiki, S. Nagashima, Y. Nishimura & M. Ohta

Abstract

This paper describes the history of old downtown Tokyo and considers the extant flood control measures in the area. Old downtown Tokyo is surrounded by several rivers, and the area itself is serviced by numerous canals. Downtown Tokyo was originally constructed on the Tone River estuary in the 1600s after the route of the Tone River was changed by local inhabitations. The canals were originally used to transport supplies from the countryside to Edo (now Tokyo), seat of national government in the 17th to 18th centuries. When the main form of transport for such goods changed from boats to vehicles in the 19th century, the unused canals were partially reclaimed. Old downtown Tokyo was a thriving commercial center before the 19th century, but the area evolved into a factory district with the development of industry in 1900s. The considerable extraction of water for industrial use caused extensive land subsidence, which combined with the deforestation of the upper Tone River, resulted in old downtown Tokyo being susceptible to flooding since the mid 20th century. Following extensive flood damage in the 1950s, old downtown Tokyo was restored and developed by the Tokyo Metropolitan Government (TMG) and the Ministry of Land, Infrastructure and Transport (MLIT) and large dikes were constructed along the Ara and Edo Rivers. Some of the canals in the old downtown areas of Tokyo were improved and restored by the TMG. Since the latter half of the 20th century, numerous high-rise office and residential buildings have been constructed on reclaimed land and in the areas that were previously flooded. Based on the historical evidence of flooding in the area, it is important for local government to do the following: (1) promote the use of high-rise office and residential buildings

Keywords

flood hazard, old downtown Tokyo, river, canal, shelter, dike, floodgate