Prior to the adoption of tsunami-specific design considerations in ASCE 7-16, research extensively examined tsunami debris transport and debris impact forces. Tsunami debris damming remains significantly less explored, with limited transient flow experiments conducted on this topic. Herein, 1:20 scale shipping containers transported via hydraulic bore freely accumulated against an instrumented column array representative of an elevated coastal structure. Resulting debris dams were analyzed through a validated photogrammetric method to estimate submerged frontal area during both accumulation and quasi-steady damming phases. A comparison with current ASCE 7-22 debris damming considerations yielded: (1) varying levels of conservatism among two different overall horizontal load prediction equations, (2) unconservative closure ratio estimates for open structures, and (3) underprediction of overall structure drag coefficients. It is proposed that bulk resistance coefficient may provide a more apt dimensionless measure of flow resistance for surface-piercing elevated coastal structure column arrays.
