Experimental investigation of debris damming loads under transient supercritical flow conditions

Debris loading during extreme flooding events has been documented by many post-tsunami field surveys of disaster-stricken communities and, as such, it is now considered and accounted for as a critical design consideration in the design of resilient infrastructure. Debris damming is one of the debris loads of concern, occurring when solid objects entrained within the inundating flow accumulate at the face of a structure or structural element. The presence of the debris dam results in increased drag loads on the structure and can have other associated effects, such as flow runup and flow accelerations, that can influence design conditions. The focus of debris damming studies has been within river engineering: therefore, previous studies have been performed in steady-state conditions. The study presented here is the first to examine debris damming in transient, supercritical flow conditions. The study uses a modified dam-break wave as the hydrodynamic forcing condition and the debris are scaled down debris types common in coastal areas (shipping containers, hydro poles, and boards). The analysis includes a qualitative examination of the difference in the debris damming mechanisms as a result of distinct flow conditions associated with a dam-break wave interacting with a surface-piercing obstacle. Additionally, the study determined the influence of the debris dam resulted in a maximum loading condition that occurred earlier and was of greater magnitude than the clear water case.