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Denver, CO, United States

Guo J.C.Y.,University of Colorado at Denver | MacKenzie K.,Urban Drainage and Flood Control District
Journal of Hydrologic Engineering | Year: 2014

When conducting a master drainage plan for an urban area, catchments are varied from small to large in size. Although there are many hydrologic methods developed for storm water predictions, the size of catchment often serves as the basis to select a proper method. As always, the common question is how to quantitatively define the size of small watershed, and how to establish the modeling consistency between the rational method for small catchments and the unit hydrograph method for large watersheds. In this study, the volume-based runoff coefficients used in the rational method are theoretically derived, and then calibrated to achieve the best agreement with the unit hydrograph method. The example of the rational method versus the Colorado urban hydrograph procedure was used to demonstrate how to achieve the modeling consistency for the metro Denver area. The same procedure can be extended into the relationships between the rational and kinematic wave methods or the rational and SCS unit hydrograph methods using the local design rainfall depths and soil loss functions. With the established model consistency, the master drainage plan can be implemented using both the rational and unit hydrograph methods for all sizes of watersheds used for drainage designs. © 2014 American Society of Civil Engineers. Source

Cox A.L.,Saint Louis University | Saadat S.,Saint Louis University | MacKenzie K.A.,Urban Drainage and Flood Control District | Thornton C.I.,Colorado State University
Journal of Irrigation and Drainage Engineering | Year: 2015

An elliptical sharp-crested weir design was developed for detention pond outlets to address discharge, pollution, and maintenance concerns. The weir was designed in an effort to efficiently pass debris through an outlet as well as having the ability to easily remove any debris attached to the weir plate. Interactions between various types of debris materials were investigated using a 1:2 Froude-scale physical model. Stage discharge data were collected to quantify reduced hydraulic efficiencies with the presence of debris in the weir plate. Nine debris tests were conducted using plastic bags, newspapers, and turf reinforcement mat material. Reductions in hydraulic efficiencies were quantified from the resulting data. Plastic bags and newspapers produced the greatest reduction in hydraulic capacity, whereas turf reinforcement mat material generated the smallest reduction. Observations regarding the ability of debris material to pass through the weir at increased flows were also made using the physical model. © 2014 American Society of Civil Engineers. Source

Heiner B.J.,U.S. Department of Interior | MacKenzie K.,Urban Drainage and Flood Control District
World Environmental and Water Resources Congress 2015: Floods, Droughts, and Ecosystems - Proceedings of the 2015 World Environmental and Water Resources Congress | Year: 2015

Extended Detention Basins (EDB) are utilized throughout storm water systems to extend the emptying time of the more frequently occurring runoff events to facilitate pollutant removal and reduce the peak runoff that would enter a storm water system. Each EDB has an outlet structure, typically installed in the embankment of the basin that contains water quality orifices, a 10-yr orifice, a sloped weir overflow with trashrack, and a 100-yr orifice downstream of the weir and trashrack to limit the amount of water that can leave the basin. Flows from the extended detention basins can be estimated by measuring the water surface upstream of the outlet. Several attempts have been made to accurately determine the flows from the detention basin outlet. Discrepancies between different methods to calculate the flow from the overflow weir lead to a physical model study to determine what method, if any, should be utilized. A complete EDB outlet structure was modeled at a geometric scale of 1:3. The model study collected data at several overflow outlet weir slopes and grate configurations. The data was used to develop a spreadsheet that can generate an outlet rating based on upstream water surface elevation that can accurately measure flow from an EDB outlet structure. © 2015 ASCE. Source

Guo J.C.Y.,University of Colorado at Denver | Shih H.M.,URS Corporation | MacKenzie K.A.,Urban Drainage and Flood Control District
Journal of Irrigation and Drainage Engineering | Year: 2012

Since the early 1990s, a water quality capture volume (WQCV) has been recommended for stormwater quality enhancement designs. However, lacking further guidance on how to shape the basin for this recommended volume, the current practice is to assume that the WQCV would lead to a satisfactory sediment trap efficiency provided that the drain time can be as long as 40 hours. In this study, the sediment trap efficiency method is modified to take basin dimension, drain time, and micropool into consideration. A water quality control basin (WQCB) should be designed with a preselected drain time and water surface area and then evaluated by its sediment trap efficiency. For a typical urban residential development with sediment particles consisting of clay, silt, and sand, a drain time for WQCB can be between 12 and 40 hours with its sediment trap efficiency varied from 60 to 80%. A drain time longer than 12 hours may result in a diminishing return on sediment trap efficiency. The performance of WQCB can be improved with a micropool. The case study indicates that a micropool can only increase the sediment trap efficiency from 80 to 89% when its storage volume increases from zero to WQCV. It implies that the major function of micropool is to control resuspended solids and buoyant debris. © 2012 American Society of Civil Engineers. Source

Guo J.C.Y.,University of Colorado at Denver | Urbonas B.,Urban Watersheds Research Institute | MacKenzie K.,Urban Drainage and Flood Control District
Journal of Hydrologic Engineering | Year: 2014

This paper summarizes the methodology and procedure used in an optimization and statistics computer model developed for determining the water quality capture volume (WQCV) for storm water best management practices (BMP) and low-impact development (LID) facility designs. TheWQCVis directly related to the local rainfall pattern, watershed imperviousness, and drain time applied to BMP/LID storage devices. Aided by a computer model, the performance of a LID/BMP basin can be predicted using the local rainfall-runoffcontinuous simulation that computes the long-term runoffvolume-based and event-based capture ratios using the principle of water volume balance among rainfall amount, hydrologic losses, andrunoffvolume captured in and bypass flow overtopping the storage basin. For a regional study, this procedure can be applied to a range of basin sizes to produce the optimized design value forWQCV. The numerical algorithmused in the computer model offers both runoffvolume capture and event capture ratios. Typically, but not always, the optimal runoffvolume and event capture ratios lie between the 80 and 90th percentile of the local runoffvolume population. The computer model used was developed as freeware for evaluating the performance of a BMP facility or producing regional design charts. The model accepts the standard hourly or 15-min rainfall data format provided by the National Climatic Data Center. Hourly data are typically available for major metro areas in the United States for a period of 20 to 60 years. © 2014 American Society of Civil Engineers. Source

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