Thanos Papanicolaou
IIHR - Hydroscience & Engineering, The University of Iowa

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Application Note: Hydraulic Structures
 
Design and evaluation: Hydraulic structures are typically used for flood control, flood conveyance, irrigation purposes, fish passage, banks protection, navigation, recreation and ecological restoration.   A hydraulic structure must meet the safety, functional and aesthetic goals for its purpose.  Thus, valuation studies must be carried out before and after the construction of the structure to assess its impacts. The structure must be of sufficient size that natural flooding is not worsened and to ensure that the structure can withstand the design flood and remain traversable.  This is required in order to protect the property and residents upstream and downstream of a structure.  In the hydraulic design, one main thing to remember is that water is dynamic.
   
Fish passage:  A study was conducted to evaluate the hydraulic performance of twenty two (22) fish-passage structures located in close proximity to bridges in western Iowa and within the HCA (Hungry Canyon Alliance) territory.  Such structures include riprap weirs, fish ladders and grouted ripraps.  The hydraulic performance of the aforementioned structures was evaluated via detailed field tests for a range of flow conditions relevant to fish migration through bridge waterways in different streams in western Iowa.  Large scale particle image velocimetry (LSPIV) technique was used for free surface flow measurements around and within the vicinity of hydraulic structures.  Knowledge of the two dimensional (2-D) free surface velocity allows engineers and biologists to determine the hydraulic performance of the above structures as it relates to fish passage.  The magnitude of the velocity will provide unique information about the level of turbulence around and within the vicinity of the structures, the approach velocity magnitude, the dissipation rate and the forces acting on juvenile and adult fish passing through the structures.  The water velocity vector magnitude and direction were calculated by dividing the estimated displacement of the particles with the time interval between two sequential images.  The LSPIV technique does not require calibration and it is well-suited for measuring in very shallow flows quickly and accurately; also can be used to estimate the discharge in conjunction with bathymetry information and assumed velocity distribution over the depth.  Validation of the LSPIV measurements was attained with the use of a SonTek flow tracker.