Effects of Riparian Forest on Disaster Prevention andPreservation of Natural Environments
Grant-in-Aid for Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||Kyoto Prefectural University|
MIZUHARA Kunio Kyoto Prefectural University, Faculty of Agriculture, Professor, 農学部, 教授 (90026401)
ISHIKAA Yoshiharu Kyoto Prefectural University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (70285245)
|Project Period (FY)
1998 – 1999
Completed(Fiscal Year 2001)
|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1999 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1998 : ¥1,800,000 (Direct Cost : ¥1,800,000)
|Keywords||riparian forest / vegetated channel / flow resistance / bed-load transport / effective tractive force / roughness concentration / stream bank erosion / promoting deposition of debris / 河川環境 / 防災 / 減勢効果 / 浸食速度 / 抵抗測|
We have investigated about 5 subjects, targeting the riparian forest where plays an important role to the environment fromation of mountainous region. A general outline of each study is explained in the following.
(1) Flow resistance in woody vegetated channels with low forest
Characteristics of flow resistance in woody vegetated channels was studies by hydraulic model experiments. With the vegetated roughness concentration, the ratio of flow depth increased in an exponentially manner, wheras the ratio of glow velocity decreased in a similar manner. Flow velocity uniformity was established in cases of high roughness cocentration. Equations for calculating friction factor were proposed.
(2) Bed-load sediment transport in woody vegetated channels
Bed-load sediment transport rate in woody vegetated channels was studied by hydraulic model experiments. As the roughness concentration of trees in channels increased, the bed-load sediment transport rate decreased. Then, the necessity of taking add
ount of effective tractive force was recongnized. Eqations for calculation effective tractive force were proposed.
(3) Effect of density of trees on drag exerted on trees in river channels
Drag exerted on trees with defferent tree densty along straight channels was measured using by hydraulic experiments. Test results indicated that the drag varies greatly with the dencity of trees × flow depth and they were correlated with te drag coefficient of velocity. Equations were obtained for deriving the drag coefficient.
(4) Characteristics of stream bank erosion in woody vegetated channels
Characteristics of stream bank erosion in woody vegetated channels was studies by hydraulic model experiments. While erosion rate of stream bed decreased, erosion rate of stream bank did not always decrease in woody vegetated channels. Especially, at the edge of water, increasing of erosion rate was found according to circumstances.
(5) Actual conditions of promoting deposition of debris caused by debris avalanches by forest zones
A number of debris avalanches occurred in southern Fukushima Prefecture in August 1998 was studiesd for the purpose of examining the functionality of forest zones for promoting deposition of debris caused by debris avalanches using aerial photo interpretation and topographic analysis. The functionality of forest zones for promoting debris deposition was confirmed. Less
Research Output (18results)