A Study Topographic Characters and Transition of Paddy Fields and Ponds in Yokohama

Abstract

To obtain basic data for a future Ecological Network plan of Yokohama, the authors studied characteristics and historical changes of distribution of rice paddies and ponds in the city. About 100 years ago, there were 7400 ha of rice paddies in Yokohama. They were located either along rivers or in narrow valleys (Yatos). Those two types of paddies occupied almost equal area. The number of the ponds in Yokohama was about 140. Most of them were agricultural irrigation ponds located at the head of Yatos. Today, the area of rice paddies has been reduced to 600 ha. Most of the agricultural ponds were filled and only 53 ponds are remaining as the ecological area within urban parks. In the ecological planning in Yokohama, one of the important issues is to conserve and restore paddies and ponds for the conservation of biological diversity.