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Sediment Control Engineering

Primal objective of sediment control operations is prevent and decrease damages from sedimentation disasters, and the development of techniques contributing to this objective is necessary. On the other hand, it is also essential matter to maintain fundamental conditions of fluvial ecosystem, consisting of water, sediment and aquatic lives. Therefore, it is necessary for us to make efforts in finding a way to control the sediment in sediment transport systems so as to satisfy both of these two extreme objectives.

In our laboratory, we are developing methods predicting and decreasing damages from sedimentation disasters, and methods evaluating impacts of sediment transport on ecosystem, from two main standpoints of "disaster prevention" and "environment".

Academic Staff

Masaharu FUJITA

Masaharu FUJITAProfessor (Disaster Prevention Research Institute)

Research Topics

By elucidating and modeling processes of production and transport of sediment as well as riverbed changes, practical plans preventing and decreasing damages from sedimentation disasters are being drawn, and effective methods and tools controlling the sedimentation systems are being developed. Some other topics on the fluvial environment related to the sediment transport phenomena which is essential to sediment control are also studied.

Contacts

Ujigawa Open Laboratory, Disaster Prevention Research Institute
TEL: +81-75-611-5263
FAX: +81-75-611-5239
E-mail: fujita@sabom.dpri.kyoto-u.ac.jp

Daizo TSUTSUMI

Daizo TSUTSUMIAssociate Professor (Disaster Prevention Research Institute)

Research Topics

Mechanism of landslide occurrence is studied by means of soil water flow calculation and slope stability analysis. Bedrock weathering and erosion are also studied by field observation and modeling approach. Throughout these studies, sediment yield in mountainous area is comprehensively studied. Dynamics of sediment in streams and its impact to habitat are also studied.

Contacts

Hodaka Sedimentation Observatory, Disaster Prevention Research Institute
TEL: +81-578-89-2154
FAX: +81-578-89-2835
E-mail: tsutsumi@sabom.dpri.kyoto-u.ac.jp

Hiroshi TAKEBAYASHI

Hiroshi TAKEBAYASHIAssociate Professor (Disaster Prevention Research Institute)

Research Topics

Stream and bed deformation analysis method, sediment (material) runoff method and prediction method of habitat for fauna and flora have been developed by clarifying mechanism of sediment transport and bed deformation. Furthermore, the method to produce sediment transport system which has a well-balanced sediment environment for both safe for our life and eco-system has been developed by use of these methods.

Contacts

Ujigawa Open Laboratory, Disaster Prevention Research Institute
TEL: +81-75-621-2144
FAX: +81-75-621-2144
E-mail: takebayashi.hiroshi.6s@kyoto-u.ac.jp

Shusuke MIYATA

miyataAssistant Professor (Disaster Prevention Research Institute)

Research Topics

My research interest is processes and behavior of water and sediment in mountainous watersheds. Based on field monitoring, laboratory tests and numerical analysis, the following research topics are examined: flash floods in mountainous rivers; modeling of snow-melt mudflows triggered by volcano eruptions; and development of a monitoring method of sediment runoff from mountainous watersheds.

Contacts

Ujigawa Open Laboratory, Disaster Prevention Research Institute
TEL: +81-75-611-5245
FAX: +81-75-611-5239
E-mail: miyata.shusuke.2e@kyoto-u.ac.jp

Research Topics

Sediment management in mountain-river-coast systems

As controls of sediment in mountain-river-coast systems, anti-sediment treatments on production areas, sabo dams, and a system of sediment flushing from reservoirs are major tools. Functions of these tools are being investigated not only from a viewpoint of sediment hydraulics but also from a viewpoint of fluvial environments.

As an example of these studies, an evaluation method for impacts of sediment flushing from reservoirs on fishes is being developed. By modeling the processes of changing habitat due to sediment deposition, anoxia and die due to turbidity after sediment flushing, the evaluating method is constructed. Figure 1 shows a relationship between concentration of turbidity, exposed duration and survival ratio of fishes.

As the other topics, evaluation method of sabo dam functions, development of new type sabo dams, study on habitat environment of fishes from a viewpoint of sediment transport, and development of a model analyzing riverbed change as a control of sediment are now focused.

graph : Relationship between concentration of turbidity, exposed duration and survival ratio of fishes
Figure 1: Relationship between concentration of turbidity, exposed duration and survival ratio of fishes

Monitoring sediment routine in mountainous watershed

Understanding sediment routine in mountainous watershed is important for the sediment management in mountain-river-coast systems. However, it is difficult to evaluate timing, location, and amount of sediment production and runoff along headwaters.

We are now developing a new method estimating the timing and amount of sediment productions by means of monitored turbidity which is closely related to the sediment production and runoff, and tracing sediment transport through numerical model calculations.

This study topic is being carried out based on field observations in Hodaka Sedimentation Observatory located on Okuhida Spa Resort, Gifu. Figure 2 shows an example of a relationship between flow rate, turbidity, and precipitation measured in a watershed. By these continuous measurements, it will be possible to record the sediment transport phenomena.

graph : Changes of precipitation, flow rate, turbidity in a watershed, during a rainstorm event
Figure 2: Changes of precipitation, flow rate, turbidity in a watershed, during a rainstorm event

Understanding and predicting sediment production in mountainous areas

In mountainous areas, sediments are generally produced by freeze-thaw effect or slope failures during rainstorm. The production of sediment is not only a starting point of sediment dynamics in sediment transport systems but also a cause of serious disasters. In this sense, it is necessary to understand the process of sediment production and to develop a method predicting its amount and timing.

As an example, we are developing a new method to predict amount of the sediment produced though the freeze-thaw effect, which is one of the dominant causes of sediment production, by means of monitored air temperature, soil temperature, soil water content, and measured soil properties.

Recently, it is pointed out that preferential water flow through soil pipes in hillslope soils might influence occurrence of slope failures. We are now investigating morphological structure, hydrological effects on rainwater flow within the soil profile, influence on slope stability and occurrence of debris flow by clogging and opining, of soil pipes.

Figure 3 shows changing distributions of soil water pressure within hypothetic hillslope soil profiles, which include a full slope length soil pipe in one case (left hand), and a pipe clogging close to downslope end in the other (right hand), obtained through numerical model simulations. These simulation results indicates that the soil pipes greatly influence the soil water response to rainfall.

image : Changing distributions of soil water pressure within soil profiles obtained through numerical model simulations
Figure 3: Changing distributions of soil water pressure within soil profiles obtained through numerical model simulations (left hand: a full slope length soil pipe, right hand: a pipe clogging close to downslope end)

Laboratory Website

http://rcfcd.dpri.kyoto-u.ac.jp/sabo/index.html