Author(s): Takashi Asaeda

Linked Author(s): Takashi Asaeda

Keywords: Riparian vegetation; DRIPVEM; Deposition area; Gravelly river; Sandy river;

Abstract: Riparian vegetation depicts the condition of river channels. Midstream channel of continental rivers is covered with tall old trees until shoreline of water, while riparian zone is covered with gravelly substrate in the midstream of the steep rivers. The difference in vegetation is caused by the difference in the sediment supply into the river channel and the sediment deposition along the river channel, which inhibits the recovery of vegetation afterwards. In this study, a dynamic riparian vegetation model (DRIPVEM), capable of evaluating the growth of riparian trees, was used to evaluate the stable condition of vegetation coverage under the condition of flood hydrology and sediment yield in to the river channel. The gravelly rivers produced vegetation coverage after 50 years, which is highly influenced by the deposition area fraction, particularly dependent on the flood level. In sandy rivers, on the other hand, flood intensity affects the vegetation coverage rather than the deposition area fraction. The low nitrogen concentration of the deposited sediment which is a detrimental factor of vegetation coverage, decreases with the nitrogen concentration of the deposited sediment in gravelly channels, as gravel deposition suppresses the re-colonization of vegetation; however, for sandy channels, vegetation coverage increases with increasing deposition area fraction as the higher nitrogen concentration accelerates the vegetation recovery. This indicates that channels having mild slopes with sandy sediments, the vegetation recovery is not suppressed after a flood, and thickly forestated until shoreline. In the steep channels with gravel sediment sources nearby, gravel deposition at flood time, suppress the recovery of vegetation.

DOI: https://doi.org/10.3850/38WC092019-0989

Year: 2019