Abstract Submission: A sedimentation and river hydraulics (SRH) 2D model was developed to perform hydraulic analysis along the Columbia River from River Mile (RM ) 102.16 to 111.73. The analysis included velocity and shear stress comparisons for 21 pile dikes located along the shoreline. Survey of the pile dikes was performed, and data was collected for model analysis, which included length, width/ thickness, and pile placement configuration. Using SRH, the pile dikes were modeled as line obstructions with an estimated thickness to compare and analyze a variety of drag coefficients and porosities (an SRH term defining the fraction of the area that is void). Multiple simulations were run using the 2-year, 100-year, and 500-year spring freshet flows. The resulting hydraulic changes were analyzed at pile dike locations by comparing models with and without pile dike representation. Model results indicated that pile dikes had an immediate effect on downstream velocity and shear stress, and varied in effective distance depending on inputs. Overall, the inclusion of the structures did not have an effect on main channel river hydraulics. Effects were only apparent in the immediate downstream conveyance area of the individual pile dike. Understanding these effects could inform river hydraulic changes including an increased risk of river lateral migration and immediate pile dike effects if pile dikes were removed or replaced with other materials (concrete or metal) or be updated with an alternative configuration This presentation will focus on the details of the modeling effort, the results, and discuss the next steps in pile dike assessment.
