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Mechanisms of maintaining cobble-bar vegetation - focused on the intensity of disturbances and the refugia of the vegetation during large floods -

维持鹅卵石植被的机制 - 重点关注大洪水期间干扰的强度和植被的避难所 -

基本信息

批准号：
23510298
负责人：
ASAMI Kayo
金额：
$ 2.25万
依托单位：
University of Hyogo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2011
资助国家：
日本
起止时间：
2011 至 2013
项目状态：
已结题

项目摘要

A vegetation monitoring study and a field survey using an image velocimetry of river flows as well as a fluid-dynamic numerical simulation have been conducted to find the effects of disturbances caused by floods of different intensities and return periods on a cobble-bar vegetation that is sustained by these disturbances. It has been found that there is an area near the downstream edge of a cobble bar where the bed shear force stays below the critical level required to move bed material and vegetation during very large flood events. This area coincided with the location where some vegetation actually survived large floods and served as a 'refugia'. Furthermore, it has been suggested that this special condition needed to maintain the cobble-bar vegetation is created by the morphologic characteristics of a sharp bend, a shortcut secondary channel and a bar with a steep-sloped downstream edge.

利用河流水流图像测速仪进行了植被监测研究和实地调查，并进行了流体动力学数值模拟，以找出不同强度和重现期的洪水引起的扰动对由这些扰动所维持的鹅卵石坝植被的影响。已经发现，在鹅卵石坝下游边缘附近有一个区域，在该区域，床剪力保持在在非常大的洪水事件中移动床沙和植被所需的临界水平以下。这一地区恰好是一些植被在大洪水中幸存下来并充当避难所的地方。此外，还提出了维持鹅卵石坝植被所需的这种特殊条件是由陡峭的弯道、捷径的次生河道和下游边缘陡峭的沙洲的地貌特征造成的。