ECOSYSTEM RESTORATION ALONG THE MIDDLE RIO GRANDE

By Joseph J. Fluder III

Just north of Albuquerque, in central New Mexico, the Pueblo of Sandia is implementing the Pueblo of Sandia Riverine Habitat Restoration Project in portions of the Sandia Subreach of the Middle Rio Grande. The project goal is to provide benefit for the federally listed Rio Grande silvery minnow, the southwestern willow flycatcher, and the Rio Grande ecosystem as a whole. When implemented, the project will contribute to the Middle Rio Grande Endangered Species Collaborative Program’s meeting the habitat restoration requirements as stated in Element S of the Reasonable and Prudent Alternatives in the March 2003 Biological Opinion, from the U.S. Fish and Wildlife Service.

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The project consists of the application of several restoration/rehabilitation techniques designed to improve aquatic habitat in the Sandia Subreach. In particular, the project seeks to enhance the availability and condition of spawning and egg retention, larval rearing, young-of-year, and over-wintering habitat for the silvery minnow by providing slackwater habitat and facilitating lateral migration of the river across bars, islands, and riverbanks during various mid-level and high-flow stages. Project construction began in fall 2010 and ended in January 2011. Specific restoration treatments will be evaluated to allow for adaptive management and the planning of potential future phases. Monitoring began in May 2011. Future potential maintenance activities are not part of this biological assessment, however.

Empirical evidence derived from habitat remediation work conducted in the Albuquerque Reach of the Middle Rio Grande suggests that silvery minnow habitat goals can be met by 25 days of inundation based on conservative estimates for egg and larval maturation. Accomplishing these goals required 1) the creation of backwaters and embayments to create slackwater areas; 2) the reduction in height of banklines, bank-attached bars, and islands; and 3) the creation of ephemeral high-flow channels to carry water into hydrologically disconnected overbank areas and bank-attached bars and islands. These actions will result in redistribution of river sediments into geomorphic units (mesohabitats) that are in balance with the existing sediment supply and hydrology at the site. Further, jetty jack lines (fabricated streambank stabilization devices) have contributed to the disconnection of overbank areas from the active channel. Natural levees have built up around jetty jack lines as the river drops sediment during the receding limb of the hydrograph. Natural levees are caused by overbank flood sedimentation and develop where there is an abrupt reduction in flow velocity, such as around jetty jacks, resulting in immediate deposition of coarser sand and silt. These natural levees reduce the connectivity between the river channel and the floodplain. The deposition of nutrient-rich sediments around the jetty jacks, as well as the accretion of similar sediments on the river banks adjacent to the jetty jacks provide ideal conditions for the colonization of these areas by non-native vegetation, particularly Russian olive. The colonization of these areas by dense vegetation causes additional decreases in flow velocities, further increasing the deposition of sediment along the channel margins. This positive loop relationship further decreases the connectivity between the channel and adjacent floodplain. Therefore, it is unlikely that flows alone would be able to remove vegetation and permit lateral reworking of the existing in-channel and channel-margin bars and islands. Mechanical interventions were required initially to form and maintain desirable silvery minnow spawning and refugia habitat.

EDITOR’S NOTE: Joseph Fluder earned his undergraduate degree in Geography at Illinois State in 1999 and subsequently took his master’s, also in Geography, at the University of New Mexico. Since then he has worked in Albuquerque for SWCA Environmental Consultants, where he now holds the position of Office Principal.


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