Abstract
This paper provides characteristics of the geomorphic features of the plain areas along historical highways on the basis of a geomorphologic examination of the route along the Kanto plain of the Nakasendo Highway, which was one of the five main highways of the Edo era. The author first maps the detailed route of the highway and then classifies landforms occurring along the highway through the stereo interpretation of aerial photographs that were taken just after World War II. The paper clarifies that the highway route appears almost straight and is usually located on terraces in the view of the entire plain scale. It is unusual that the route is found in mountains, hills, and the alluvial plain. Precise geomorphic analyses lead to the following conclusions. On the terrace, the highway route seldom crosses the dissected valley and follows the watershed in the middle of the terraces. The route on fans is an outward arc in shape parallel to contour line. The route was constructed on the natural levee in the alluvial plain so as not to cross the former rivers, back marshes, and present rivers. Based on these characteristics, the author concludes that the highway route was in the control of accessibility and safety against water hazards. However, accessibility took priority over safety at a few places.
