摘要：We studied the effects of a catastrophic flood and debris flow on third- to fifth-order segments of the Black River system (Ozark Mountains, Missouri, USA). The event scoured the channel and riparian areas in upper sections of the study area and resulted in an estimated 80-90% reduction in taxonomic richness and abundance of the macroinvertebrate assemblages. In lower sections that were 10 km or more distant from the entry point, the stream was not physically altered but a substantial amount of sediment was deposited and stream turbidity was elevated for months after the event. Reduced taxonomic richness and altered assemblage composition were evident in the upper study area four months after the flood and debris flow, but substantial recovery had occurred by nine months post-event. In the lower study area, the disturbance appeared to have minimal effects on macroinvertebrates. Multi-metric index scores and pre-event/post-event compositional similarity comparisons also suggested that biological impairment was limited to stream segments nearest the entry point of the flood and debris flow.
