Health & Environmental Research Online (HERO)


Print Feedback Export to File
8040470 
Journal Article 
Ecological responses to anthropogenic alterations of gravel-bed rivers in Japan, from floodplain river segments to the microhabitat scale: a review 
Nakamura, F; Kawaguchi, Y; Nakano, D; Yamada, H 
2008 
Yes 
Developments in Earth Surface Processes
ISSN: 0928-2025 
Developments in Earth Surface Processes 
11 
501-523 
WOS:000311042600020 
We describe the relationship between disturbance regimes, the life history traits of aquatic and riparian organisms, and effects of human activity, using Japanese gravel-bed rivers in the Asia Monsoon Belt as an example. The consideration of various roles of disturbance in creating a spatial and temporal pattern of habitats is made hierarchically at three spatial scales. Segment scale is the largest, represented by a braided river landscape on an alluvial fan. Riparian tree species direct their life history strategies to survive in the shifting habitat dynamics. Reservoirs constructed at the fan apex regulate flood disturbances and seasonal flow variation, changing the dynamic state to a monotonous, static habitat structure. Intermediate reach-scale structures are represented by pool-riffle sequences, gravel bars, secondary and abandoned channels and oxbow lakes. We focused particularly on the lateral variation of the entire valley floor and its stream channel, which provide critical habitats for spawning, hatching, rearing, wintering, feeding and dwelling as well as flow refugia for fish and macroinvertebrates. Bed instability resulting from an increased tractive force due to channel straightening and its impact on macroinvertebrate communities is also discussed. Finally, the smallest scale is the microhabitat seen as the interstitial spaces in gravel beds used by salmonid and benthic fish for all or some of their life stages. Sediment control dams and gravel mining in rivers and floodplains is causing gravel-size sediment starvation, whereas the introduction of fine sediment is substantially increased following land-use development.