Characteristics of floodplain vegetation invading on different channel morphology and its effects on long-term channel dynamics

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15095
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: Toyama Prefectural University (2021); Hokkaido University (2019-2020)
• Principal Investigator: Tomoko Kyuka 富山県立大学, 工学部, 准教授 (50751236)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 河道内樹木 / 種子 / 河床・流路変動 / 植生流失

Outline of Final Research Achievements

To understand the characteristics of floodplain forestation, and the accompanying channel morphodynamics, first, using aerial photographs, UAVs and satellite images, long-term changes in land classification was determined. Second, several laboratory flume experiments were conducted to identify the seed dispersal and settlement property, and morphodynamics associated with vegetation growth rate. Third, to estimate the physical parameters governing the relationship between flow and seed establishment, two-dimensional analysis was performed with the addition of a seed model and a vegetation growth model. The results showed that new vegetation invasion and expansion could not be explained only by physical flow parameters such as discharge and water depth. Vegetation seeds were left behind on the sandbar edge during the discharge decreasing stage, regardless of the difference in channel morphologies, seed’s density, and size.

Free Research Field

河川工学

Academic Significance and Societal Importance of the Research Achievements

植生が河床・流路変動に与える影響に関する報告は多数存在するものの，動的に変化する植生群落を対象とし，出水や流路形態に起因する長期変化を物理パラメーターから説明した報告は非常に限られている．本研究では，複数のアプローチより，河道内樹林化が進行する際の物理パラメーターを明らかとし，植生の新規侵入や分布は流れの物理パラメーターのみでは説明できず，出水時の土砂移動に伴う河床形状を考慮する必要があることが示された．得られた成果（前半時期の結果，後半はこれから）は国内学会や国際会議，論文（国内，国際誌）として報告しており，河道内樹林化が河川管理上課題となる諸外国においても，十分なインパクトが期待できる．