We developed versatility- and simplicity-conscious landscape evolution models (LEMs) and applied them to actual topography in Japan to predict topographic change. The development of LEMs requires that geomorphic transport laws (GTLs) express uplift/subsidence, river erosion, mass movement on slopes, and sea erosion. We reviewed previous studies on LEMs and in related fields, and selected those GTLs most suitable to the aim of this study and incorporated them into the LEMs. We applied the LEMs to the actual topography in a Japanese coastal area and simulated the topographic changes that would occur during two glacial–interglacial cycles. The LEMs reproduced some theoretically predicted topographic changes, such as the formation of marine terraces by uplift, changes in drainage, and generation of a drainage network. We examined the influence on topographic changes of differences in coefficients and parameters related to river and sea erosion. As drainage indexes became larger, channels meandered more and the drainage network increased in complexity. The result is consistent with previous research. However, marine terraces seemed to form earlier under conditions of a faster uplift rate or a gentler angle of the seabed. This means that the formation age of a paleo-shoreline should depend on the specific site conditions of its location in the general area. Differences in formation age also lead to differences in the formation elevation of the paleo-shoreline. The result is inconsistent with the traditional interpretation of Japanese geomorphologists that the formation age and elevation of the paleo-shoreline must be homogeneous across an area in order to discuss whether a phenomenon actually occurs or not, or to what extent. We require more advanced LEMs based on investigations of actual topography and geology, observations of actual topographic changes, theory construction, and technical development.
抄録全体を表示