2006 Fiscal Year Final Research Report Summary
Development of evaluating method for the relationship between sedimentation, flood disturbance and river plant dynamics
| Project/Area Number |
17560452
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
水工水理学
|
|---|
| Research Institution | Saitama University |
|---|
Principal Investigator |
TANAKA Norio Saitama University, Graduate School of Science and Engineering, Associate Professor, 大学院理工学研究科, 助教授 (80323377)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
YUTANI Kentaro Saitama University, Graduate School of Science and Engineering, Research Associate, 大学院理工学研究科, 助手 (00344953)
|
|---|
| Project Period (FY) |
2005 – 2006
|
| Keywords | Plant dynamics / flood disturbance / gravel bed river / sand accumulation / Eragrostis curvula / Phragmites japonica |
|---|
| Research Abstract |
The research was conducted to elucidate the relationship between plant dynamics on a gravel bed river or wetland and flood disturbance. For wetland, Zizania latifolia was selected and for gravel bed river, Eragrostis curvula and Phragmites japonica was selected.
Field observation was conducted to elucidate the effect of Eragrostis curvula on the threshold of gravel movement at midstream of the Arakawa River. Under various hydraulic conditions (particle diameter, bed slope and water depth) and growth conditions (colony diameter and density of the plant), Shields parameter of the gravel in the plant-vegetated area was estimated using the drag characteristics of the plant and calculated friction velocity affected by the plant. Threshold of gravel movement of median grain size (d50) and d84 (84% of the grain weight) around the plants was evaluated by comparing friction velocity of the flow condition with the critical friction velocity of the diameter. The removal threshold of Eragrostis cur
… More
vula was defined at which the friction velocity affected by the plant's drag is equal to the critical friction velocity of d84. The threshold condition related to HI (H・water depth, I・bed slope) and the drag by plant was validated for a flood in the Arakawa River and for two floods in the Yoshino River.
The effect of flood disturbance on the morphology of runners, plant productivity and runner-expansion characteristics of Phragmites japonica was investigated at midstream of the Arakawa River. The dynamic growth model of P. japonica was developed considering the effect of disturbance, i.e., the difference of runner morphology and shoot productivity in the parent colony. The aboveground biomass distribution along the distance from the parent colony was well represented by the model. For analyzing the effect of flood disturbance interval, maximum water levels at three flood events were calculated and evaluated whether the habitat of P. japonica were inundated or not. In addition, the threshold friction velocity of the average grain diameter was compared with the friction velocity at the flood event. Although the gravel movement possibility has a little different, tendency with the damaged situation of P. japonica, the clear relationship between the flood interval and the productivity in each habitat is found. The analysis indicates the possibility to calculate the plant productivity under the effect of flood disturbance. Less
|
