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Long-term shoreline changes of the Kita-shitaura and Miura coasts were investigated on the basis of the aerial photographs and field observations. Beach erosion has been severe on the Kita-shitaura coast, because of the recurrent dredging of the navigation channel of Kita-shitaura fishing port and the disposal. In contrast, on the Miura coast, dredged materials were placed on the shoreline, resulting in widening of the foreshore. Thus, in this area, sand balance has been lost due to the anthropogenic factors. To improve this situation, the recycling of dredged sand is required instead of constructing hard structures.

Beach changes on the Narusawa, Taga and Kawarago coasts in Hitachi City in Ibaraki Prefecture were investigated on the basis of the aerial photographs and field observation. The shoreline changes between 1984 and 2006 were studied. Sea cliff extends along these coasts, and narrow sandy beaches have been formed mainly by the sand supply from small rivers. The breakwaters of Kawarago port and Ohse fishing port were constructed, resulting in the formation of the wave shelter zone. Longshore sand transport from outside to inside the wave shelter zone was induced, causing erosion outside the wave shelter zone and accretion inside it. In the eroded zone, sea cliff is exposed to waves and abrasion by gravels is underway. To protect these beaches, comprehensive management such as the sand recycling is required.

Beach erosion and accretion of the south Kujukuri coast was investigated based on the aerial photographs and field observation. The sand supply by northward longshore sand transport has been decreasing on this coast, causing erosion of the south part of the coast close to the sand source (sea cliff). In contrast, on the north end of the coastline, a long breakwater of the Katakai fishing port was extended and a large amount of sand has been deposited in the wave shelter zone. Furthermore, the ground subsidence up to 60cm occurred along the coastline due to the pumping-up of the ground water to obtain the water-soluble gas. The coastal situation of the south Kujukuri coast has devastated year by year due to all these impacts. To save the coast, full scale sand nourishment is required.

The Seisho-bypass highway runs along the Seisho coast facing the Sagami Bay. On September 6, Typhoon 0709 attacked this coast with rough waves, and the road of this highway was severely damaged over 1.1km length, resulting in full traffic stoppage. During this typhoon, maximum significant wave height reached 6m with a wave period of 14s. Damages of the road were investigated through the field observation. Strong waves attacked the coastline from the Southeast, which is in contrast to the ordinary wave direction of the Southwest. Due to this oblique wave incidence, westward longshore sand transport was developed. Along this coast, the submarine canyons develop at several locations, and part of sand transported by longshore sand transport is considered to be flowed out of the submarine canyons, causing net loss of sand.

Beach changes around the mouth of the Magome River on the Enshu-nada coast and the long-term deformation of Nakatajima sand dune were investigated. The dune material originates from the Tenryu River. The supply of fine sand from this river has decreased owing to the construction of the dams in the upstream basin of the river, and the coastal forest was excessively planted close to the shoreline, resulting in decreasing sand supply from the shoreline to the sand dune. Thus, this sand dune has significantly been starving. To conserve this sand dune, supply of new sand or reuse of sand is required.

Disappearance of sandy beach caused by the excess development of coastal forest was investigated along the Kujyukuri coast facing the Pacific Ocean. Since World War II, coastal forest has been created to prevent damages due to wind blown sand. However, coastal forest zone was excessively widened in the natural sand dune areasas well as the construction of protection facilities of themselves such as an earth dike, increasing potential against beach erosion. Furthermore beach erosion took place due to the decrease in longshore sand supply. Thus sandy beach of Kujyukuri coast has narrowed by these causes.