open access

https://hdl.handle.net/2115/46197

Impacts of dam-regulated flows on channel morphology and riparian vegetation : a longitudinal analysis of Satsunai River, Japan

英語

Aerial photographs

2011-01

Springer Japan

Landscape and Ecological Engineering

7(1)

65-77

We examined the impacts of the Satsunai River Dam on the hydrology and development of riparian vegetation along the upper and lower reaches of the Satsunai River downstream from the dam. We estimated frequency curves of the flood discharge during the pre-dam (1976-1996) and post-dam (1997-2006) periods and simulated the flood frequency at sampling points within sites under pre-dam, post-dam and dam-removal (using the pre-dam flood discharge and post-dam cross-sections) scenarios. Changes in channel morphology and land cover were investigated by analyzing aerial photographs. Our results indicate that the 20-year flood at the upper site decreased substantially (from 599 to 271 m3/s) after dam operation, while that of the lower site decreased slightly (from 1025 to 977 m3/s). Within the upper site, the proportion of 20-year return periods increased considerably (from 31.0 to 48.6%) while the proportion of 1- to 20-year return periods decreased (from 30.5 to 8.9%) after dam operation. Flood frequency results for the dam-removal scenario were similar to those for the pre-dam period, suggesting that a return to pre-dam discharge rates would restore the pre-dam distribution of flood frequency at the upper site. Within the lower site, however, the distribution of flood frequency varied little between the pre- and post-dam scenarios, because tributary inflows between the sites mitigated the impacts of dam-regulated flows. Land cover types were associated with flood frequency at both sites. The reduced flood frequency of the upper site resulted in increased area of riparian vegetation and decreased area of active channel.

学術雑誌論文

Accepted Manuscript

The final publication is available at www.springerlink.com

1860-1871