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Hydraulics Lab: 2009-2010

Hahn Arroyo Rehab


Final Modeling Report


Draining approximated 6.5 square miles before entering the North Diversion Channel, the Hahn Arroyo plays a vital role in conveying flood water in North Eastern Albuquerque.  Since its construction in the 1960s, the channel has deteriorated significantly.  The Albuquerque Metropolitan Arroyo Flood Control Authority (AMAFCA) has begun the rehabilitation of the Hahn. As part of this rehabilitation, AMAFCA would like to include measures to improve water quality or best management practices (BMPs).  AMAFCA engineers have designed a structure to be installed as an island in the channel (Figure Below).  However, due to the unpredictable nature of supercritical flow occurring in the Hahn Arroyo, AMAFCA engineers have requested the assistance of the University of New Mexico’s (UNM’s) Hydraulics Lab.  AMAFCA Engineer, Kevin Daggett, and research assistants have tested and improved two structures.  The structures were designed to remove debris efficiently up to the 1-year storm. 




South Diversion Channel Drop Structure


Final Modeling Report



The Albuquerque Metropolitan Arroyo Flood Control Authority (AMAFCA) has actively introduced structural debris removal to storm water facilities as a Best Management Practice in recent years.  The upstream portion of AMAFCA's South Diversion Channel (SDC) collects storm water runoff from the area east of Interstate 25 and south of the University of New Mexico area.  The SDC receives water from storm drains, the Genievas Arroyo, and the Kirtland Arroyo, before crossing I-25.  A concrete baffle chute is located on the channel approximately 800 feet downstream of the I-25 crossing.

The SDC is an earth-lined trapezoidal channel with a bottom width of 30.0 ft and ripraped side slopes.  The Channel has a longitudinal slope of 0.14% just upstream of the baffle chute.  The Manning's roughness coefficient of the channel is estimated to be 0.035.  Although the channel has been designed for a discharge of 3450 cubic feet per second (cfs), the most frequent discharges vary between 100 and 600 cfs. 


AMAFCA’s goal is to divert flow at the upstream end of the existing concrete structure and remove debris from the flow before allowing the it to return to the SDC.  A physical model has been constructed to test diversion and debris removal alternatives.  Several improvements have been made to the structure to achieve desired hydraulic performance.


Supercritical Lateral Outlet Flow

Various lateral outflows from supercritical channels are tested to assist in determining design guidance with respect to:  angle of lateral outflow, guiding vanes, and ratio of outflow to channel flow.



CFD simulation results 45 degree lateral outlet with tapered vane