Beach Changes Around a Sand Spit —The Example of Mihono-Matsubara—

Abstract

ABSTRACTTopographic changes around Mihono-matsubara Compound Spit were studied based on bottom sounding data and aerial photographs. On the Shizuoka and Shimizu coasts located upcoast of the sand spit, erosion waves are generated due to interruption of longshore sand transport from the construction of coastal structures. The propagating velocity of these erosion waves were found to range 0.5 to 0.8 km/yr. This agrees considerably well with the theoretically estimated value of 0.47 km/yr. Comparison of beach profiles showed that the dominant beach changes take place at depths shallower than –7 m, and this provides the closure depth for profile changes on this coast. The longshore sand transport rate was evaluated to be 1.3 × 105 m3/yr at specific locations on the Shizuoka and Shimizu coasts. This littoral transport rate was compared to the values from Fuji and Suruga coasts located in Suruga Bay. It is concluded that the littoral transport rate at the Fuji coast, located at the head of Suruga Bay, is large...