An apparatus or biopassage (A) includes a housing (20) dimensioned for receipt in a waterway during an increased flow event. The housing has a passage: (26) that provides a region of reduced flow generally irrespective of the flow external to the passage. A flow disrupter (50) disturbs laminar flow in the waterway above the passage. A preferred embodiment of the disrupter includes surfaces (52, 54) disposed in angled relation relative to a common apex (60) located above a longitudinal opening (30passage. The surfaces include a series of peaks and valleys formed by angled planar portions (56) in one arrangement. A deflector (NC) is positioned upstream of an inlet end (40) of the passage to direct water away from the passage.