Using fish as an ecological indicator to assess the advantage and disadvantage of constructed groynes

Hui-Ling Yu ； Shang-Shu Shih

《濕地學刊》 7卷1期 (2018/12) Pp. 42-51

摘要

Riverside groynes provide shelter for fish during flood period and an area for feeding and resting during normal flow periods. This study employs the TABS-2 model and weighted usable area (WUA) model to examine the riverbed morphodynamics and fish habitat quality around and behind riverside groynes. The dimensionless relationships between WUA and groynes' aspect ratio, Froude number and sediment transport capacity are also established. We found that the slow-motion area behind groynes increases and, thus, enlarges the WUA for fish during flood periods. However, years later, sediment deposition occurs due to the lower sediment transport capacity in these areas and point to the reduction of WUA. Conversely, the results in the normal flow period indicate that the WUA decreases after installing groynes. Flood discharge plays a major role in the morphodynamics around and behind groynes while normal discharge with tidal current only contributes a minor effect. According to the findings of this study, we suggest an effective habitat management such as regular sediment excavation.

關鍵字

numerical model ； groynes ； fish ； morphodynamics