|
Hokkaido University Collection of Scholarly and Academic Papers >
Graduate School of Agriculture / Faculty of Agriculture >
Peer-reviewed Journal Articles, etc >
Large wood, sediment, and flow regimes: Their interactions and temporal changes caused by human impacts in Japan
This item is licensed under:Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Title: | Large wood, sediment, and flow regimes: Their interactions and temporal changes caused by human impacts in Japan |
Authors: | Nakamura, Futoshi Browse this author →KAKEN DB | Seo, Jung Il Browse this author | Akasaka, Takumi Browse this author | Swanson, Frederick J. Browse this author |
Keywords: | Regime shift | Channel incision | Forest expansion | Sediment discharge |
Issue Date: | 15-Feb-2017 |
Publisher: | Elsevier |
Journal Title: | Geomorphology |
Volume: | 279 |
Start Page: | 176 |
End Page: | 187 |
Publisher DOI: | 10.1016/j.geomorph.2016.09.001 |
Abstract: | Water, sediment, and large wood (LW) are the three key components of dynamic river-floodplain ecosystems. We examined variations in sediment and LW discharge with respect to precipitation, the presence of dams, land and river use change, and related channel incision and forest expansion on gravel bars and floodplains across Japan. The results indicated that unit sediment discharge and unit LW discharge were smaller in southern Japan where precipitation intensity is generally much greater. Effective precipitation, an index that takes current and antecedent precipitation into account, was a strong predictor of discharge in small watersheds, but not in larger watersheds. However, precipitation intensities related to unit sediment discharge in intermediate and large watersheds were smaller than those associated with unit LW discharge, which we attribute to differences in particle shape and size and also transport mechanisms. The relationship between river flow and discharge of sediment and LW lead us to posit that discharges of these components are supply limited in southern Japan and transport limited in northern Japan. The cross-sectional mean low-flow bed elevation of gravel-bed and sand-bed rivers in Japan decreased by similar to 0.71 and 0.74 m on average, respectively, over the period 1960-2000. Forest expansion on bars and floodplains has been prominent since the 1990s, and trees apparently began to colonize gravel bars similar to 10 to 20 years after riverbed degradation began. Forest recovery in headwater basins, dam construction, gravel mining, and channelization over the past half century are likely the dominant factors that significantly reduced downstream sediment delivery, thereby promoting channel incision and forest expansion. Changes in rivers and floodplains associated with channel incision and forest expansion alter the assemblages of aquatic and terrestrial organisms in riverine landscapes of Japan, and climate change may contribute to this change by intensified precipitation. Additionally, regime shifts of water, sediment, and LW may continue or they may reach a dynamic state of quasi-equilibrium in the future. Continued monitoring of these three components, taking into account their geographic variation, is critical for anticipating and managing future changes in river-floodplain systems in Japan and around the world. (C) 2016 Elsevier B.V. All rights reserved. |
Rights: | ©2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ | http://creativecommons.org/licenses/by-nc-nd/4.0/ |
Type: | article (author version) |
URI: | http://hdl.handle.net/2115/72715 |
Appears in Collections: | 農学院・農学研究院 (Graduate School of Agriculture / Faculty of Agriculture) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
|
Submitter: 中村 太士
|