Exterior deformation is one of the most important items to measure when managing the safety of embankment dams. A conventional surveying method, using targets installed on the crest and the slopes of the embankment dams, is usually employed to measure exterior deformation. It is difficult, however, to measure the deformation by such a method immediately after an earthquake or other emergency. A displacement monitoring system using GPS (Global Positioning System) was developed to continuously monitor the deformation of dams. The system can provide three-dimensional displacements at many points simultaneously with high accuracy at the millimeter level. Ishibuchi Dam is a concrete-face rock-fill dam; it is one of the oldest rock-fill dams in Japan. After the large settlement caused by the Iwate-Miyagi Nairiku Earthquake of 2008, the above GPS displacement monitoring system was installed to continuously monitor the deformation behavior. On March 11, 2011, the Great East Japan Earthquake struck near the northeast coast of Honshu Island. This paper describes the results of the deformation monitoring of Ishibuchi Dam before, during, and after the Great East Japan Earthquake, and discusses the validity of the system for the safe management of dams after earthquakes.

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Towards the establishment of a method for structural soundness evaluation of concrete dams focusing on their vibration characteristics change, natural frequency changes of dam body were investigated throughout microtremor measurement and earthquake motion record analysis. Based on the results, a physically-based multiple regression model was proposed and discussed for trend estimation of natural frequencies considering the effects of reservoir water depth and external temperature changes those should be separated from the effects due to deterioration or damages.

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Sedimentation process in the Joumine Reservoir located in the semi-arid area of North Tunisia was studied by numerical simulation. The major sediment component flowing into the reservoir is fine silt of about 5 μm in diameter, and the high SS water carried by floods generates high-turbid current along the reservoir bed. A vertical 2-D flow model was developed to simulate the high-turbid flow, and the model performance was verified by comparison with the data obtained from field measurements. The model reproduced the longitudinal profile of bed deformation for 23 years after the dam construction fairly well. The computation showed the unsteady sedimentation process, in which the small and middle scale floods result in sediment deposition in the upstream reach while the self-accelerating gravity current caused by the large scale floods picks up and transports the sediment downstream to the deepest area near the dam body.

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