Abstract: Frequent breaches of check dams occur on the Loess Plateau during extreme rainstorms. It is crucial to evaluate the low flood control standards of check dams, the significant infiltration enhancement at the interface, and the breach mechanisms triggered by hydraulic forces during such extreme rainfall events. This study employs field investigations, on-site monitoring, and laboratory experiments to examine water-induced damage and breach mechanisms in check dams within typical small watersheds used for gully control and land reclamation. The research aims to elucidate the failure modes of check dams, the seepage characteristics of the dam body, and the progressive breach mechanism. The results indicate that typical water-induced failure modes of check dams can be classified into two main categories: dam deformation and dam failure. Dam deformation includes crest settlement and slope collapse, while dam failure can be further subdivided into three types: piping-induced dam break, slope slip-induced dam break, and overtopping-induced dam break. The unique geological structure of check dams leads to distinct seepage behaviors within the dam body, resulting in progressive water-induced damage characteristics. The loose composition of the dam body facilitates intense seepage, leading to material softening, crest settlement, and progressive slope collapse. Additionally, weak interfaces between excavation and fill layers are prone to forming dominant seepage pathways, causing deformation and failure along these weak zones. During extreme rainstorms, intense seepage within the dam body and enhanced preferential flow at the interface sharply increase pore water pressure. The resulting seepage forces rapidly erode soil along the interface, triggering piping failure within the dam body. Furthermore, rapid shearing along the interface area leads to sliding failure of the dam structure. These findings clarify the hydraulic excitation mechanism responsible for the frequent collapse of check dams on the Loess Plateau due to interface-induced failure.