Native American methods for conservation and restoration of semiarid ephemeral streams

ABSTRACT:

Combined effects of brush encroachment and channel entrenchment in the Southwestern United States threaten ecological, hydrological, and agricultural functions of ephemeral streams and associated alluvial surfaces. Restoration is difficult because entrenchment is widespread, and highly variable flow magnitudes defy standardized structural approaches. Methods developed by the Zuni Indians during more than 2,000 years of farming on dynamic alluvial fans combine brush removal with ephemeral channel-erosion control and show promise for effective watershed-scale conservation and restoration. Zuni utilize several types of simple brush structures that rely on hydraulic characteristics of woody material to modify erosive and depositional effects of both small seasonal and irregular storm-flow events. Zuni brush structures are inexpensive and quick to build, require no external material inputs, and avoid the extensive disturbance associated with conventional rigid check-dam construction. Successive surveys at three incised-headwater ephemeral channels on the Zuni Indian Reservation showed that Zuni techniques increased the incidence of overbank flow during small streamflow events (acting as permeable check dams) and large floods (moving downstream and forming debris jams) and thereby helped reconnect channels to alluvial fans. Zuni brush structures represent a potential alternative to capital- and labor-intensive approaches to semiarid watershed conservation and restoration.