Water resource shortage in water-scarce areas is effectively alleviated, and people's livelihood and well-being are significantly improved by long-distance water diversion projects. However, under complex operating conditions, adverse flow patterns including vortices and backflows are prone to be formed in canal systems, thereby inducing overtopping or intense fluctuations that cause scouring damage to the wetted surfaces of water conveyance and distribution structures. To explore flow stabilization schemes and their performance under complex operating conditions, the intense hydraulic oscillation induced by high-velocity flow in the “Y-shaped” diversion and drainage layout at steep slope outlets was analyzed, the causes of water surface fluctuations and the core mechanism of hydraulic oscillation were elucidated by engineering case studies and physical model tests: when high-energy flow entered the closed-boundary energy dissipater, a standing wave system was formed on the drainage side, which induced obvious intermittent “gate slamming and surging” at the drainage sluice. Based on the principles of “energy dissipation” and “flow pattern reconstruction”, two novel wave-damping engineering measures, including wave-damping plates and flow-guiding plates, were proposed. The formation conditions of standing waves were blocked through targeted wave regulation, and reliable control of hydraulic oscillation was therefore realized. Experimental results show that the wave reduction ratio is approximately 70% under low flow conditions, 60% under medium flow conditions, and 78%~84% under high flow conditions for the wavedamping plate scheme; under the deflector scheme, the wave elimination amplitude is found to be approximately 70% under small flow rates, 55%~75% under medium flow rates, and around 70%~80% under large flow rates. It is concluded that remarkable wave-damping effects are exhibited by wave-damping plates and flow-guiding plates, by which reliable data references can be supplied for engineering optimization design and practical hydraulic oscillation problems in engineering can be effectively solved. Important technical support can be provided for the safe design and operation of similar water conveyance structures by the research findings.