大潟海岸における漂砂の観測

Abstract

Field investigations were conducted to find characteristics of the nearshore bottomconfiguration and sand drift off the Ogata coast. Some of the resulting data are discussedin this paper.In order to map features nearshore, a new program of surveying the bottom topogr-aphy was established and the first survey was made on Jnly 20-25, 1967 by echo soundingmethods. The survey showed that crescentic type bars, known as rhythmic bar pattern, are found in the surf zone. The relationship between wave action and topographic response, as shown by development and movement of such bars has not yet been made clear, buta short consideration of this problem is then followed with plans for future study.In order to find the characteristics and volume of the suspended sediment, its con-centration was measured by observations from a pier 300 meters long. The samples wereused to estimate the diffusivity of sediment due to wave action and to compare the volumeobtained by the bamboo sampler.It is concluded that the value of the diffusion constant obtained from the estimate isof the order of 10~ cm5/sec, and that the sample volume by the bamboo sampler isapproximately in proportion to the concentration of the suspended sediment.