Impacts of road crossings on headwater streams in an urban landscape

Urban streams are plagued with degraded riparian zones, multiple sources of pollutants, and rapidly changing hydrology and land use.  Although riparian buffer zones are commonly implemented, direct inputs from road crossings over streams may negate this measure.  The impacts of the first road crossing on headwater streams was examined in nine urban streams in Gainesville, Florida by measuring sediment particle size, morphology, organic matter storage, metal accumulation and macroinvertebrates above and below the crossing.  Morphological changes downstream of crossing were characterized by pools, followed by deeply incised channels.  Increased flows associated with incised streams resulted in decreased organic matter storage downstream of the crossings.   Filterers, scrapers and non-insect groups increased downstream of the crossing and collector-gatherers were more common upstream due to the greater availability of organic matter.  Road crossings alter habitat structure and hydrology of stream ecosystems, thus creating a shift in physical and biological structure between up and downstream section.  Understanding these changes can guide best management practices in development of new roads in Florida.