Abstract: With accelerating urbanization and aggravating global climate changes, urban flood disasters occur frequently. It is theoretically and practically of great significance to study the characteristics of flood discharging on urban streets and grasp the mechanism of how it is influenced by urban buildings. This study has conducted a series of physical model tests focusing on the influence of urban buildings on flood water movement, arranging water outlets on both sides of the main street to simulate lateral flow diversion between the buildings of discontinuous distribution. For the main street flood flow, the influence of the outlet locations on its pattern transition is analyzed; a detailed observation and analysis are made on the dynamics of the transition from supercritical to subcritical flow and its responses to changes in upstream inflow and diverting outlet locations. We find the parameters of the hydraulic jump－such as jump location, jump form, roller length, conjugate depth ratios, and discharge ratio－behave quite differently from those of the classical hydraulic jumps.

Key words: urban streets, flow pattern transition, hydraulic jump pattern, physical model test, diverting flow