The geomorphic legacy of water and sediment control structures in a semiarid rangeland watershed

Authors: Nichols, Mary; MAGIRL, C. - Us Geological Survey (USGS); SAYRE, N.F. - University Of California; SHAW, J.R. - Colorado State University

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2017
Publication Date: 12/18/2017
Citation: Nichols, M.H., Magirl, C., Sayre, N., Shaw, J. 2017. The geomorphic legacy of water and sediment control structures in a semiarid rangeland watershed. Earth Surface Processes and Landforms. 43:909–918. https://doi.org/10.1002/esp.4287.
DOI: https://doi.org/10.1002/esp.4287

Interpretive Summary: The Buenos Aires National Wildlife Refuge in southern Arizona was established in 1985 with a primary goal of restoring grassland habitat of the endangered Masked Bobwhite (Colinus virginianus ridgwayi), a subspecies of quail. Currently, channel incision, gullying, headcut advance, and erosion are challenges to grassland restoration. Prior to the establishment of the refuge, the landscape was managed as a commercial cattle ranch. Water supply for ranching operations was enhanced by construction of numerous stock ponds, water spreader berms, and lateral channel berms, and concrete spillways. Many of these structures have been compromised and contribute to eroding the landscape. An inventory of water control structures remnant of historic cattle ranching was assembled for the refuge and an assessment of structural condition based on aerial imagery was completed. Of 19 identified lateral channel berms, 63% have been breached and 21% have been flanked, and 20% of 190 shorter water spreader berms have been breached and 13% have been flanked. This information is critical for understanding limitations of restoration efforts and will help in developing achievable ecosystem and restoration management plans.

Technical Abstract: An inventory of water and sediment control structures remnant of historic cattle ranching was assembled for the Buenos Aires National Wildlife Refuge (BANWR) in southern Arizona, USA. An assessment of structural condition based on aerial imagery identified headcut initiation and channel incision associated with compromised lateral channel berms, concrete water control structures, and floodplain water spreader berms as threats to floodplains and associated habitat. Of 19 identified lateral channel berms, 63% have been breached and 21% have been flanked, and 20% of 190 shorter water spreader berms have been breached and 13% have been flanked. Identifying the cause of recent gullying and channel incision is critical for future land management and habitat restoration on the BANWR as well as for downstream restoration efforts. Although gullying induced by unmaintained structures threatens large areas of productive grassland habitat, in some cases onset of disturbance is recent enough that opportunities for mitigation can be identified and potentially damaging erosion trajectories can be altered.