Effects of fine sediments on dynamic nature of the hyporheic zone

2014 Fiscal Year Final Research Report

• Project/Area Number: 24780153
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Forest science
• Research Institution: Kyushu University
• Principal Investigator: KASAHARA Tamao 九州大学, (連合)農学研究科(研究院), 准教授 (10622037)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 河川間隙水域 / 細粒土砂 / 伏流

Outline of Final Research Achievements

The hyporheic zone plays several important roles in stream ecosystems. It is a dynamic zone, yet few studies examined the factors controlling its change in extent. In this study, vertical hydraulic head gradient (VHG) and fine sediment concentration in the hyporheic zone were monitored to investigate the dynamic nature of the hyporheic zone. The study sites were located in step-pool sequences in steep headwater streams. During precipitation events, pressure from hillslope increased, and the upwelling trend increased, whereas VHG did not change in the downwelling zone. Fine sediment concentration in the downwelling zone increased after the high flow events, but hydraulic conductivity did not changed and stayed high. Therefore, contrary to previous understanding, the extent of the hyporheic zone was stable in steep headwater streams, though the concentration of fine sediments and fraction of organic matter changed during high flow event, so the environment changed over time.

Free Research Field

Riparian hydrology and biogeochemistry