Aquatic Organism Passage (AOP) in Culvert Design

Fish Passage and Abundance around Grade Control Structures on Incised Streams in Wester Iowa

  • John Thomas (Hungry Canyons Alliance)
  • Mary Culler (Iowa State University)
  • Dimitri Dermisis (University of Iowa)
  • Clay Pierce (USGS)
  • Thanos Papanicolaou (University of Iowa)
  • Tim Stewart (Iowa State University)
  • Chris Larson (Iowa Department of Natural Resources)


Land use changes and channelization of streams in the deep loess region of western Iowa have led to stream channel incision, altered flow regimes, increased sediment inputs, decreased habitat diversity, and reduced lateral connectivity of streams and floodplains. Grade control structures (GCS) are built in streams to prevent further erosion, protect infrastructure, and reduce sediment loads. However, GCS may have a detrimental impact on fisheries and biological communities if they present a barrier to fish passage. Three complementary biological and hydraulic studies on the effects of GCS in these streams are reviewed. GCS with steep (≥ 1:4 rise:run) downstream slopes severely limited fish passage, but GCS with gentle slopes (≤ 1:15) allowed greater passage. Following modification of GCS to reduce slopes and permit increased passage, IBI scores increased and several species were detected further upstream than before modification. Total macroinvertebrate density, biomass, and taxonomic diversity, and abundance of ecologically sensitive taxa were greater at GCS than in reaches immediately upstream, downstream, or ≥ 1 km from GCS. A hydraulic study confirmed results from fish passage studies; minimum depths and maximum current velocities at GCS with gentle slopes (≤ 1:15) were more likely to meet minimum criteria for fish passage than GCS with steeper slopes.

How to Cite:

Thomas, J. & Culler, M. & Dermisis, D. & Pierce, C. & Papanicolaou, T. & Stewart, T. & Larson, C., (2014) “Fish Passage and Abundance around Grade Control Structures on Incised Streams in Wester Iowa”, National Hydraulic Engineering Conference 2014 1(2014).

Rights: Copyright © 2014, John Thomas, Mary Culler, Dimitri Dermisis, Clay Pierce, Thanos Papanicolaou, Tim Stewart, and Chris Larson

Publisher Notes

  • Panel moderated by Bart Bergendahl, FHWA.
  • About the Presenters: John Thomas has been with the Hungry Canyons Alliance since 2000 and all of his work revolves around stream instability and grade control. Mr. Thomas has a B.S. in geology from Cornell College, a master’s degree in geology and water resources from the Iowa State University, and a master’s degree in civil engineering (hydraulics) from the University of Iowa.

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Published on
20 Aug 2014
Peer Reviewed