Urban Drainage and Flood Control District

West Pleasant View, CO, United States

Urban Drainage and Flood Control District

West Pleasant View, CO, United States
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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.

Earles T.A.,Wright Water Engineers Inc. | Guo J.,University of Colorado at Denver | MacKenzie K.,Urban Drainage and Flood Control District | Clary J.,Wright Water Engineers Inc. | Tillack S.,Wright Water Engineers Inc.
Low Impact Development 2010: Redefining Water in the City - Proceedings of the 2010 International Low Impact Development Conference | Year: 2010

Regulations in the United States establish water quality protection requirements that typically are targeted at relatively small, frequent events, comprising the bulk of non-point source pollutant loading to receiving waters. Although water quality requirements vary from municipality to municipality, typical requirements include promoting infiltration to reduce runoff volume and peak flows, storage and release of runoff or some combination of infiltration and storage/release. Examples of such requirements include ordinances requiring development to maintain runoff rates and, in some cases, volumes at pre-development levels for up to a specified design event and/or requirements to capture, store and release runoff from frequent events. Complying with these types of water quality requirements can be expensive, so it is understandable to question what benefit these requirements have for flood control. Flood control benefits of water quality facilities typically can be quantified using hydrologic and hydraulic calculations; however, there are important considerations that belie the simplicity of calculations, including ownership, operation and maintenance of facilities. These issues are especially important for on-site water quality facilities and "distributed" controls, which generally are not publicly owned and maintained. This paper presents hydrologic and hydraulic modeling to explore water quality and flood control benefits of water quality facilities, especially infiltration-based Low Impact Development (LID) practices. The paper presents a method for calculating an Imperviousness Reduction Factor (IRF) that can be used to calculate effective imperviousness based on total site imperviousness. This paper demonstrates that while water quality facilities are important for smaller, more frequently occurring events and play a role in water quality and stream channel protection when it comes to larger flooding events, hydrologic benefits diminish and must be complemented with sound detention, conveyance and floodplain management policies and practices. Failure to recognize and plan for this fact will inevitably subject properties to higher than appropriate flood risk. © 2010 ASCE.

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.

Guo J.C.Y.,University of Colorado at Denver | MacKenzie K.A.,Urban Drainage and Flood Control District | Mommandi A.,Research Office
Journal of Irrigation and Drainage Engineering | Year: 2016

Types C and D inlet grates have a large surface area to drain storm runoff collected along highway medians. As always, highway debris presents a clogging problem to these area grates. Under the assumption that debris would be accumulated on the water surface, an inclined angle was applied to an area grate. It is hoped that the submerged portion of the area grate will remain open to drain stormwater. The selection of inclined angle should be related to the hydraulic efficiency and the amount of floating debris in stormwater. However, there is not any quantifiable guidance as to how to choose the inclined angle for an area grate. In this study, a series of inclined angles, ranging from 0 to function as a horizontal grate to 90° to operate like a side grate, is investigated for flow interception capacity. A new set of orifice and weir formulas with an inclined angle is derived from energy principles and then tested in a 1/3-scaled model in laboratory. The method of leastsquare error was used to identify the best fitted values for discharge coefficients as a function of inclined angle with or without an inlet depression. The set of new equations derived and calibrated in this study can significantly improve the current design procedures for Types C and D grates used for highway median drains. © 2016 American Society of Civil Engineers.

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.

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.

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.

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