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Hydraulics Lab: 2008-2009

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 Outflow


 IAHR 2009 Conference Proceeding Paper



Supercritical channels present a number of design issues as the flow is readily disturbed.  Yet, the design of supercritical channels for storm water drainage is necessary in steep environments.  Storm drains flowing into supercritical channels are typically aligned to minimize the angle between the drain and the channel.  By doing so, standing waves are minimized.  Channels are often designed with additional freeboard downstream to accommodate the standing wave. 

In contrast, flow can be removed from channels via storm drain pipes for the purpose of Best Management Practices consisting of storm water cleaning such as debris removal and/or natural filtration.  We will present a number of physical models showing that channels flowing near design capacity are not adversely affected by lateral outflow.  However, in the same channels, low to moderate flows with lateral outflow result in a rooster tail wave in the channel.

In this study, 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.



Physical model for the 45 degree angled outlet


The backwater due to the vane can be ignorable.  With this vane dimension of the model, the backwater does not affect to the upstream boundary of the numerical domain.  Time dependent x-directional velocity is shown with colored surface plot and streamlines in the figure shown as below.



CFD simulation results 45 degree lateral outlet with tapered vane



El Bordo Siphon


 Draft numerical modeling note


image011 image013


Junction Box Plan View and longitudinal section view (see the construction plan sheet 7/8)


With the current junction box design, flow will be delivered safely. After approximately 40 seconds, the box outlet flow rate (300 cfs) is getting stable (see the plot below). Very high velocity (12 ft/s) was simulated under the 5’ DIP (red colored region in the figure below). See the time series simulation results (3D view). However, the inlet boundary condition (6 ft/s velocity with fully filled flow area) is an imaginary condition. Design flow rate and velocity are needed.

Flow retention due to the junction box is expected. To test backwater impact to upstream, the numerical model domain (8’ RCP part) needs to extend.




Field Temperature Assessment for Artificial Turf Alternation


Full modeling report

Purpose and Backgrounds

Artificial turf is growing in popularity in semi-arid regions as demands on water resources increase. The Albuquerque Metropolitan Arroyo Flood Control Authority (AMAFCA) and Bernalillo County are exploring the possibilities of playing fields made of artificial turf rather than natural grass, specifically in detention ponds.  The University of New Mexico carried out a previous experiment demonstrating the highly buoyant nature of the artificial turf.  Research during that experiment raised concerns about the increased air temperatures above the artificial turf.  The purpose of this experiment is to study the differences in air temperature above natural grass and artificial turf. 


Measuring field temperature using Kestrel 4500 Pocket Weather Tracker



Although artificial turf is appealing for playing fields because of its low maintenance and water savings, there are other factors to consider.  Artificial turf is warmer than natural grass.  In semi-arid settings, this could be a concern for young athletes.  It might be worthwhile to conduct a similar experiment at a larger scale.