The purpose of this study is to quantitatively estimate the erosional properties for cohesive sediment from Saemankeum artificial lake. A series of erosion tests were conducted with Chonbuk annular flume, which is the first one constructed in this country and verified with validities. Each erosion tests were conducted under a uniform bed condition but a different bed density respectively, and its critical shear stress for erosion(${ au}_{ce}$) as well as the erosion rate coefficient (${varepsilon}_M$) were determined quantitatively. Since the erosional properties of the cohesive sediments vary largely depending in the physico-chemical properties, such properties of Saemankeum sediments were also estimated and their effects on the erosional properties were analyzed. For Saemankeum sediments, it can be seen that ${ au}_{ce}$ increases from $0.26N/m^2$ to $0.52N/m^2$ and ${varepsilon}_M$ decreases exponentially from $14.28mg/cm^2;hr$ to $6.02mg/cm^2;hr$, as the bed density varies from $1.17g/cm^3$ to $1.34g/cm^3$. The erosional parameters of Saemankeum sediments are found to be remarkably different in quantity as compared with those for cohesive sediments from other sites. Particularly, ${ au}_{ce}$ for Saemankeum sediments is known to be larger than that of Kunsan sediments but similar with that of Shihwa sediments, while ${varepsilon}_M$ for Saemankeum sediments is shown to be smaller than that for Kunsan sediments.