A consequence of the current global warming is rising sea level as Glacial ice melts. The future effect of such sea level rise on shorelines, river deltas and river long profiles is not well known. The problem may be understood by studying the consequences of Holocene sea level rise after the last glaciation. The melting of the Pleistocene glaciers caused a sea level rise of ～ 120 m, mostly in a period of 12,000 years. Here the effect of rising sea level on river deltas and long profiles is explored numerically for the Fly-Strickland River System, Papua New Guinea for Holocene sea level rise. The result shows that the Fly-Strickland River system likely went into autoretreat in response to Holocene sea level rise, and is now recovering. The effect of river size on delta response to Holocene sea level rise is also studied for three rivers, of which initial river lengths are 400km, 600km and 800km, respectively. The comparison of the three rivers indicates that the shorelines in all rivers transgress about 500 km by the time sea level stabilizes at high stand, but the prograding speeds of new deltas depend on the feed rate from upstream and therefore the delta of the large river recovers more rapidly than that of the small river.

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Characteristics of inner structure of hericoidal flow in turbulent open channel flow with longitudinal ridge elements which are set up on the bottom wall with a space of twice the depth of water is investigated by using flow visualization techniques. The results indicate that large-scale longitudinal vortical structures are formed over the ridges, and relative smaller vortical structure are formed near the center of the trough which is the wall region between the ridge elements. The large-scale longitudinal vortical structure over the ridges possess a longitudinal length between 3H and 4H, and a transverse width between 1.0H and 1.5H, where H is depth of the water. The formative regions of both structures remain for long period and correspond to relative low speed region and the relative high shear region in which two direction primary velocity shear (∂U /∂y,∂U /∂z) exist. Further, it becomes clear that these longitudinal vortical structure generate acceleration and deceleration of instantaneous primary velocity, instantaneous secondary flow and Reynolds stress. On the basis of these results, it is concluded that these longitudinal vortical structures lead to properties of the mean flow and turbulence of the flow field.

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Because an explicit scheme is generally applied to the cord of the distinct element method which is essential for the numerical movable bed, when flow resistance increases under complicated boundary condition, overlap of particles become excessive to cause abnormally violent repulsion of particle. As a remedy of this fault, the cord is changed substantially by introducing an implicit scheme into the routine of contact-force calculation between particles. The refined cord reproduces the physical experiment of collapse of the column which consists of cylinders, as well as the conventional explicit code. Furthermore, even for granular flow on very steep slope, the solution of which is unstable by an explicit scheme, the refined cord shows a good performance.

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In recent years, several field observations of wave set-up at a river mouth have been reported. From those results, it can be concluded that the height of wave set-up has a dependence on the morphology at a river entrance. However, quantitative relationship between the magnitude of wave set-up height and river mouth morphology has not been thoroughly clarified yet because of insufficient acquisition of river mouth morphology data. In this study, laboratory experiment, as well as theoretical discussions, is carried out to investigate quantitative relationship between wave set-up height and river mouth depth. Furthermore, detailed discussions are made for the relationship between wave set-up height and river mouth morphology at the Shiribetsu River mouth, where oblique photographs have been taken almost every week. Effectiveness of jetty construction is also investigated from the viewpoint of wave set-up height.

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Water and sediment quality change experimental study was done for eight months using water and sediment in a reservoir. On the condition that the oxygen in water is saturated, in the -9～-11cm depth layer, organic nitrogen and organic phosphorus in the sediments were decrease. Anmonium nitrogen, inorganic phosphorus and total iron in the porewater increased compared by initial values. These results show that the organic matter in the sediments were dissolved and removed in the porewater. The anaerobic condition by nitrogen proceeded. On the condition that the oxygen in water is saturated, the concentration of iron in the water was low value, but in the the -9～-11cm depth layer, the anaerobic condition by iron proceeded. Characteristic of anaerobic reservoir sediment condition change was similar to paddy field and lake.

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