|Shields Jr, Fletcher|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2001
Publication Date: N/A
Interpretive Summary: Gullies often form at the interface between stream corridors and cultivated fields. These gullies erode and extend into fields, generating sediments that pollute downstream waters and degrade aquatic habitats. One widely-applied control measure is to block the gully with an earthen dam. Water drains through an L-shaped metal culvert that extends through the embankment. To date, several thousand of these structures, known as drop pipes, have been designed and placed along streams in Mississippi and similar regions without consideration of environmental (i.e., habitat) factors. Sixteen drop pipe sites in northwestern Mississippi were sampled for vertebrate species (fish, amphibians, reptiles, birds, and mammals). Site design and management were assessed by surveying site physical characteristics and sampling terrestrial vegetation. Animal populations within drop pipe sites were larger and more diverse at sites greater than 0.22 acre in size more woody vegetation, and larger pools or ponds. Sites with attractive habitat (large area, woody vegetation, pool area) yielded 65 to 82 vertebrate species, while smaller sites yielded only 11 to 20 species. These findings may be used to design and manage drop pipes to reap greater ecological benefits.
Technical Abstract: Stream channel incision often triggers formation of tributary gullies. Standard practice for controlling gully development involves damming with an earthen embankment with drainage provided by an L-shaped metal pipe. To date, thousands of these structures, also known as drop pipes, have been constructed in riparian zones adjacent to agricultural areas, but environmental criteria have played no role in design. Sixteen drop pipe sites in northwestern Mississippi were sampled for fish, amphibians, reptiles, birds, and mammals; and physical habitat characteristics were assessed by sampling vegetation and surveying site topography. Results indicated that the riparian vertebrate communities within drop pipe sites were positively associated with increasing levels of habitat area, pool development, and vegetative structure. Speciose sites (those yielding 65 to 82 vertebrate species) were relatively large (>0.09 ha), with a significant pool area. Depauperate sites (only 11 to 20 species captured) were smaller, with no pool area and little woody vegetation. Considerable environmental benefits could be realized by slightly modified design and management of drop pipe structures.