Study on Change in River Landscape in Alluvial Fun Rivers and Its Restoration

本项目的目的是建立预测和评价冲积性河流景观变化的方法，这些河流的泥沙供应和洪峰流量都因水坝建设而减少。首先，利用野外数据、水槽实验和数值模拟对河流中观察到的几个单独主题进行了研究。其次，探讨了河流中树木对地貌变化的响应等综合过程，以寻求合适的河流恢复方法。研究结果总结如下：1。两河之比较——特多里河与阿部河利用调查资料和航空照片比较了特多里河与阿部河的地貌和植被面积的变化。两条河流在冲积河段的流域面积和河床坡度几乎相同。Tedori河有一个大型水坝，但Abe河没有。结果表明，洪涝洪峰流量的增加会导致河道内植被的繁盛。植被区地貌和生长的过程详细研究了以下过程。(1)植被沟道的输沙过程(2)植被生长模式与地下水位和沉积河床物质的关系(3)洪水对植被的破坏和/或优势这些研究强调了植被、地貌和水状况之间相互作用的重要性。洪水洪峰流量降低对植被生长的影响进行了模拟，以评价大坝建设引起的景观变化。该模型成功地预测了特洛里河植被的繁盛，将成为讨论河流景观变化的有力工具之一。生境变化的评价方法IFIM/PHABSIM方法经过改进，加入了一个鱼类不同生命阶段的合成思想。该方法还与泥沙输运模型相结合，探讨了地貌和植被格局变化对生境的影响。在上述结果的基础上，讨论了对环境无害和具有成本效益的河流恢复方法。少

The aim of the project is to establish the method to predict and evaluate the change in river landscape in alluvial fun rivers where both sediment supply and peak discharge of floods have been decreased due to dam constructions. First, several individual topics observed in the rivers have been investigated using field data, flume experiments and numerical simulations. Second, the synthesized processes including the response of trees in a river to the change of the geomorphology have been discussed in order to seek proper restoration method of the rivers. The results have been summarized as below :1. Comparison between two rivers -The Tedori River and The Abe RiverThe changes in geomorphology and vegetated area in the Tedori River and those in the Abe River have been compared using survey data and aerial photographs. The two rivers have almost same drainage area and bed-slope in an alluvial reach. The Tedori River has a large dam, but the Abe River does not. The results show that the de … More crease of the peak discharge in floods causes the thriving of vegetation in a channel.2. Processes of geomorphology and growth of vegetated areaThe following processes are investigated in detail.(1) Sediment transport process in a channel with vegetated area(2) Patterns of growing vegetation area concerned to ground water level and deposited bed-material(3) Flood damage and/or advantage on vegetationThese investigations have emphasized the importance of the interaction among vegetation, geomorphology and water regime.3. Modeling of vegetation dynamics due to decrease of peak discharge in floodsThe effect of the decrease of peak discharge in floods on the growth of vegetation has been modeled in order to evaluate the changing landscape due to dam constructions. The model has successfully predicted the thriving of vegetation in the Terori River, and it would be one of powerful tools to discuss the change in river landscape.4. Evaluation method of changing habitatThe IFIM/PHABSIM method has been modified by adding the idea for synthesis of several different life-stages of a fish species. The method has also been cooperated with sediment transport model in order to discuss the effects of the change in geomorphology and vegetation pattern on the habitat.5. Toward restorationThe environmentally sound and cost-effective methods for the restoration of the rivers have been discussed base on the results shown in the above. Less