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Hydraulics Lab: 2002-2003

Storm Water Debris Removal Structure Design at West Bluff


Full modeling report

Appendix D – Numerical Modeling



          The West Bluff pond storm water drainage channel was designed by AMAFCA to be located at the intersection of Juniper and Amor Dr. in northwest Albuquerque.  The designed channel will play the role of the storm water controller, especially removing the floating debris from the storm water. The channel was designed for the peak 100-year design flow rate, 663 cfs for the open channel part (upstream), and 682 cfs for culvert (in a pipe shape) inflow part (downstream).  To prevent storm water debris from entering the existing channel, a baffle and weir combination structure was designed in the drainage channel.  This controlled storm water in upstream channel will be merged to the downstream channel. The design engineers wanted confirmation that the designed baffle and weir combination structure would keep storm water debris effectively, and the drainage channel would behave as they designed.



Figure 1: Location Map



          The objective of this project was to build a scale model of the West Bluff pond storm water drainage channel design, to use the laws of similitude to simulate the safety of the design, suggest design modifications.  For this objective, the maximum preventing debris capacity was focused on the baffle and weir device experiment, and the simple and smooth flow streamline that decreases the flow dead zone was simulated in the channel model.



  Figure 2: Main Channel Experiment, 1:16          Figure 3: Baffle and Weir Experiment, 1:1



          The modified baffle and weir combination structure can prevent the most floating debris from the entering river-bound storm water.  The wedge and stair should be constructed at this combination structure, and the distance between baffle and weir should be decreased to improve retention of debris. The weir should be constructed horizontally in elevation throughout the channel instead of sloping the channel bed.  In addition, the collected storm water debris could be cleaned easily after a storm event, since the modified channel made simple streamlines and removed flow dead zones around the entrance of the upstream channel.  The side weir and channel should be extended at least 56 feet to decrease the water surface elevation to prevent overtopping of the design water surface elevation.  The curved wall was offset slightly from the culvert exit and straightened, the culvert-dividing wall was removed, and riprap should be added on the channel bed.  The full-scale model SMS simulation result is in Figure 5 below. The streamline is simple so we can conclude that the modified model is a reasonable design. 


Figure 4: As-design Model and Modified Model



Figure 5: Two-dimensional numerical simulation