Long-term changes in riparian forest cover under a dam-induced flow scheme: the accompanying a numerical modelling perspective

Abstract River regulation affects downstream riparian vegetation dynamics. This paper investigates changes in vegetation cover along a steep reach of the Kitakami river in Japan, below the Gosho dam. Historical aerial imagery covering 60-years of both the pre- and post- dam construction phases is used to document land cover evolution. Changes in riparian forest cover are evaluated in relation to the corresponding hydrological regimes. A long-term trend in forest cover encroachment was revealed and a temporal correlation analysis confirmed a clear association with the modified water and sediment regime downstream of the dam. In addition, a numerical simulation of changes in spatial tree distribution using the dynamic riparian vegetation model (DRIPVEM) was undertaken. Validation of the simulation using the Kappa statistic showed a moderate-to-substantial agreement between model output and the photographic record.