A rectangular net type armar unit( Marin-mat) with rubble in it is proposed to prevent the scouring. The unit is implemented practically in a small space and the construction speed becomes relatively short.. In the paper the stability number in stormy waves Ns is derived in a series of hydraulic experiment using 1/50 marine mat models. The experimental results demonstrate the Ns number become about 3 to 4. Secondary Isbashh formula is adapted for tsnami flow test to investigate the coefficient y. The coefficient y becomes about 0.8 by analusis of damage ratio test in tsunami action.In the both experiments the allowable damage ratio is approximated to be 2%.