Stormwater Design Research Articles

Runoff Characteristics for Construction Site Erosion Control Practices

Controlling soil erosion during and after construction is a major concern due to the impacts of sediment on stream water quality, and many studies have focused on the effectiveness of erosion control best management practices (BMPs) to prevent erosion. However, their ability to reduce runoff volume and peak discharge is not commonly studied or integrated into storm water designs due to lack of data and design guidelines. This study investigated runoff characteristics (total runoff, peak flow rate, curve number, and rational method runoff coefficient) from bare compacted soil conditions with and without erosion control BMPs, with an emphasis on compost erosion control blankets (CECBs), at three different slope (2H:1V, 3H:1V, and 4H:1V). Experiments were performed in the San Diego State University, Soil Erosion Research Laboratory on a 3-m by 10-m indoor titling soil bed using simulated rainfall based on conditions specified in ASTM D-6459. Eleven erosion control BMPs were evaluated at a slope of 2H:1V, thr...

Economic Impacts of Alternative Approaches to Storm-Water Management and Land Development

This paper explores how estimated construction costs and projected revenue from sales could influence the decision to maintain open spaces in predevelopment condition and to implement a decentralized swale-based storm-water management system characteristic of low impact development. Four development alternatives were explored for a hypothetical residential subdivision. Hedonic price analysis was used to develop a price equation for the Gainesville, Fla. residential market. The hedonic analysis indicated that reduction in lot size to preserve open-space and conversion from a curb and gutter storm-water drainage system to a swale-based system would both result in a lower sale price per lot. Estimated construction costs indicated that this same combination of site planning and storm-water system design would result in the lowest per lot construction cost. The ratio of revenue (sale price) to construction cost showed that a development incorporating lot size reductions for open-space preservation and a swale-based storm-water management system was the preferred option over the first half of the study period, but was not in the second half.

Expanded analytical probabilistic stormwater models for use in watershed and master drainage planning

In watershed and master drainage planning studies, information on flood frequency distributions must be available for locations throughout the study area and for conditions with and without planned stormwater control facilities. Design storm modeling and continuous simulation approaches are used to obtain the required information. Analytical probabilistic stormwater models are computationally more efficient alternatives but they were developed originally for urban stormwater management planning and design purposes. In this paper, methods and strategies are developed to expand the capabilities of existing analytical probabilistic stormwater models so that they can also be used in watershed and master drainage planning studies. The case study tests and validates the proposed methods and strategies and demonstrates the versatilities of the new approach.

Effect of Aggregation of On-Site Storm-Water Control Devices in an Urban Catchment Model

Spatially distributed on-site devices such as detention tanks and bioretention are becoming more common as a means of controlling urban storm-water quantity and quality. One approach to modeling the cumulative catchment-scale effects of such devices is to resolve the catchment down to the scale of a land parcel or finer, and then to model each device separately. This involves computational and input data demands that may be impracticable, especially in planning or preliminary design stages of storm-water system design. To reduce these demands, the spatial resolution can be coarsened by aggregating land parcels and devices, but this may compromise model accuracy. The focus of this study was examination of the effects of aggregation on predictions of water quantity and quality (for a representative contaminant, total suspended solids) for detention, infiltration, and bioretention devices. A detailed model for urban storm water improvement conceptualization simulation was set up for a 0.83 km2 catchment wit...

Modelling urban river catchment: a case study in Malaysia

Generally, many rivers within urban catchments in Malaysia are being altered from their natural states to meet the demand of developments. Most of these rivers have also become the receiving water body for urban drainage systems. Therefore, it has become extremely difficult to separate river from the rest of the drainage system. Study of interaction between such river and urban drainage is necessary for urban drainage planning and design. Present study showcases how urban river modelling using InfoWorks Collection System (CS) on Berop River, Perak (Malaysia), can assist stormwater system design. Calibrated using historical flood event, the developed model was used for evaluation of various design storms, possible scenarios as well as existing and future landuse condition. The study found that within a data scarcity condition, InfoWorks CS played a significant role in providing good platform for stormwater system modelling as well as satisfactory simulations and analyses for complex combination of river and urban drainage stormwater system. This is the much needed advantage for practising engineers in time saving stormwater system design.

Retrofitting Detention Basin with Water Quality Control Pool

Many detention basins built before 1990 are not equipped with storm-water quality control device. With the latest developments in low impact development for storm-water management, these existing detention basins need modifications on their outlet structures to increase on-site runoff treatment and disposal. An outlet shall be designed to have, at least, three levels of release, including water quality release over 12–48 h, low flow release for 10-year event, and 100-year high flow release. All these efforts are to aim at the full spectrum runoff treatment that is not only to capture the minor and major events but also to store microevents. Over the years, the empirical methods under different assumptions have been developed for determining the design storm-water quality control volume (WQCV). To improve the consistency in storm-water detention designs, this paper presents a mathematical model that produces the synthetic runoff-volume capture curves normalized by the local average rainfall event-depth. A runoff-volume capture curve defines the relationship between WQCV and runoff capture ratio on a long-term basis. A higher runoff capture ratio requires a larger storage volume. Using the runoff capture curve as the basis, the WQCV can be consistently determined for the preselected runoff capture target such as the 80% recommended by the U.S. Environmental Protection Agency in 1986. A case study illustrates how to retrofit an existing outfall concrete vault with a perforated plate and a micropool for WQCV. With a three-level release control, the outfall box can have a slow release for microevents and a fast release for extreme events. This procedure has been recommended for designing a new basin and retrofitting an existing one for the metro Denver area. Details can be found in the UD-DETENTION computer model available at www.udfcd.org at no cost to download.

Variation of Extreme Storm Surges with Wind Field Model and Future Typhoon Change in Stochastic Typhoon Simulation

Stochastic typhoon simulation, that is the combination of the Monte Carlo simulation on typhoon parameters, the storm surge simulation with the parameters, and the extreme-value analysis on the storm surges, is one of useful tools in the probabilistic discussion on the current design storm water level for coastal defense. This paper compares the extreme storm surges on the Pacific coast from Kyushu to Kanto District, Japan, with two empirical parametric typhoon wind field models, two sea surface drag coefficients for high wind speed, and two assumptions of future typhoon change. The result shows that the extreme storm surge is very sensitive to the sea surface drag coefficient for high wind speed and that one of the assumptions gives larger extreme storm surges in some of the coast and smaller in others.

Development of Storm-Water Management Design Criteria to Maintain Geomorphic Stability in Kansas City Metropolitan Area Streams

Fifty-three years of historical precipitation data were applied to the U.S. Environmental Protection Agency Storm Water Management Model (SWMM) to conduct hydrologic and hydraulic simulations, generating continuous stream flow hydrographs in the receiving stream channels. On-site BMP and regional detention criteria were selected to allow postdevelopment replication of predevelopment peak flow frequency exceedance curves and the critical portions of shear stress duration curves. Instream continuous stage data generated by SWMM were used to examine erosion potential through the use of an erosion potential index. Coarse stream bed material were found to be less sensitive to changes in erosion potential due to urbanization, and extended detention ponds designed for flood control and water quality treatment were effective in reducing erosion potential. These controls were less effective in reducing erosion potential of fine loam bed material, indicating reductions of runoff volumes are required to minimize increases in channel erosion. Findings indicate that regional analysis based on local hydrologic and geomorphic characteristics are necessary to identify appropriate storm-water control requirements.

Volume-Based Imperviousness for Storm Water Designs

The concept of low impact development (LID) is to apply decentralized on-site runoff source control to preserve the watershed hydrologic and ecological functions. An integrated layout using bioretention and vegetated landscape can decrease the developed runoff volume and peak flow. One of the key factors in urban hydrology is the imperviousness in the watershed. The conventional approach is to weight the imperviousness by the subareas in the watershed. Obviously, the area-weighted method has become inadequate when coping with LID because LID takes the flow path into consideration. When an impervious area directly drains onto a pervious area, the area-weighted method fails to count for the additional soil infiltration loss. In this study, the conventional area-weighted method is modified with a paved area reduction factor that converts the area-weighted imperviousness to its effective imperviousness. A family of curves was also developed for engineering applications. When a cascading process is introduced to the runoff flow path, the paved area reduction factor can be determined using the impervious to pervious area ratio and the infiltration to rainfall intensity ratio.

Split-flow theory: Stormwater design to emulate natural landscapes

This article reviews the development and application of existing stormwater management theories with a focus on emulating natural on site hydrological processes and discusses the design intentions, merits, and weaknesses of each theory. A new stormwater management theory is then proposed using elements found in each of these existing theories. This new theory proposes to systematically split runoff into three volumes and evaporate, infiltrate and discharge; and manage these volumes in ways that emulate natural hydrological site processes, thereby creating stormwater management systems that are more ecologically based. The intent is to provide a stormwater management theory that can be used to emulate natural processes of evapotranspiration, infiltration, and runoff and, by extension, emulate pre-development stormwater rate, quality, frequency, duration, and volume. The article then discusses limitations of this theory, including lack of established methods, need for evaluation against existing methods, obstacles to implementation under current regulations, and suggested additional research.

Sustainable Stormwater Design in the Midwest

Sustainable Stormwater Design in the Midwest

Low Impact Development Practices: A Review of Current Research and Recommendations for Future Directions

The low impact development (LID) approach has been recommended as an alternative to traditional stormwater design. Research on individual LID practices such as bioretention, pervious pavements, and grassed swales has increased in recent years. Bioretention cells have been effective in retaining large volumes of runoff and pollutants on site, and consistently reduced concentrations of certain pollutants such as metals. However, retention of certain pollutants such as nitrate–nitrogen and phosphorus has been problematic. Porous pavements have been extremely effective in infiltrating stormwater runoff. Concerns have been raised about groundwater contamination, but research has shown that this is not a problem in most settings. Green roofs have been found to retain a large percentage of rainfall (63% on average) in a variety of climates. A common thread across bioretention, green roofs and grassed swales was found: the export of phosphorus. The issue appears to be linked to high phosphorus levels in the soil media, or possibly to fertilization of turf or planted areas. Solutions to this problem have been recommended. Contrary to popular belief, research has shown that bioretention and pervious pavements continue to infiltrate even with frost in the ground. Although issues have been identified with retention of certain pollutants, the LID approach has been found to result in increased retention of stormwater and pollutants on site, mimicking pre-development hydrologic function. Future research needs have also been identified.

Evaluation of sediment control pond performance at construction sites in the Greater Toronto Area

Receiving water quality concerns associated with increased construction activities in recent years in the Greater Toronto Area has prompted the Toronto and Region Conservation Authority (TRCA) to evaluate design criteria for sediment control ponds employed during the construction period. Stormwater management ponds located in the towns of Richmond Hill and Markham were monitored to obtain stormwater runoff quantity and influent-effluent quality data during site development. The ponds were designed and constructed in accordance with the Ontario Ministry of the Environment Stormwater management planning and design manual 2003 for an enhanced level of protection (i.e., 80% total suspended solids removal). A hydrodynamic and sediment-transport model was used to examine the effect of pond geometry on sediment removal efficiency under varying storm events. The monitoring data and the modelling results clearly demonstrate the importance of proper pond size and geometry design. This paper focuses on the effect of the ratio of pond length to pond width in minimizing the short-circuiting effect and improvement of the sediment removal efficiency of stormwater management ponds. The results of this study will be useful in updating the design criteria for stormwater management ponds.Key words: stormwater, management, pond, design, sediment.

BMP Analysis System for Watershed-Based Stormwater Management

Best Management Practices (BMPs) are measures for mitigating nonpoint source (NPS) pollution caused mainly by stormwater runoff. Established urban and newly developing areas must develop cost effective means for restoring or minimizing impacts, and planning future growth. Prince George's County in Maryland, USA, a fast-growing region in the Washington, DC metropolitan area, has developed a number of tools to support analysis and decision making for stormwater management planning and design at the watershed level. These tools support watershed analysis, innovative BMPs, and optimization. Application of these tools can help achieve environmental goals and lead to significant cost savings. This project includes software development that utilizes GIS information and technology, integrates BMP processes simulation models, and applies system optimization techniques for BMP planning and selection. The system employs the ESRI ArcGIS© as the platform, and provides GIS-based visualization and support for developing networks including sequences of land uses, BMPs, and stream reaches. The system also provides interfaces for BMP placement, BMP attribute data input, and decision optimization management. The system includes a stand-alone BMP simulation and evaluation module, which complements both research and regulatory nonpoint source control assessment efforts, and allows flexibility in the examining various BMP design alternatives. Process based simulation of BMPs provides a technique that is sensitive to local climate and rainfall patterns. The system incorporates a meta-heuristic optimization technique to find the most cost-effective BMP placement and implementation plan given a control target, or a fixed cost. A case study is presented to demonstrate the application of the Prince George's County system. The case study involves a highly urbanized area in the Anacostia River (a tributary to Potomac River) watershed southeast of Washington, DC. An innovative system of management practices is proposed to minimize runoff, improve water quality, and provide water reuse opportunities. Proposed management techniques include bioretention, green roof, and rooftop runoff collection (rain barrel) systems. The modeling system was used to identify the most cost-effective combinations of management practices to help minimize frequency and size of runoff events and resulting combined sewer overflows to the Anacostia River.

Triple-bottom-line assessment of water sensitive design options in a greenfield residential area

This paper presents the results of a study from Brisbane, Australia, where the relative merit of seven stormwater management design options that could be applied in typical, greenfield, medium density residential areas were assessed using a triple-bottom-line assessment framework. This framework involved assessing the financial, ecological and social dimensions of each option in consultation with stakeholders. The assessment process included the use of multicriteria analysis, a multidisciplinary expert panel, a local social survey of residents who lived adjacent to alternative design options, two workshops involving typical citizens of Brisbane, consultation with traditional stakeholder groups, pollutant export modelling, and water reuse modelling. The scope of issues investigated during the process was very broad. In addition, the information obtained from the community survey and public workshops is likely to be indicative of commonly held views of residents in cities similar to Brisbane. The multicriteria analysis stage of the assessment highlighted both large and small constructed wetlands as having the greatest overall net value compared to other options in the Brisbane region. However, the expert panel’s preferred design option at the end of the process was bioretention systems located within the median strip of roads. Reasons for this discrepancy are explored.

Evolution of Ontario's Stormwater Management Planning and Design Guidance

Abstract Ontario's Stormwater Management, Planning and Design Manual released in March 2003 integrates some of the advancements made in stormwater management since the 1994 version of the Manual was published. Perhaps the most significant update is the recognition of in-stream erosion control and water balance objectives in addition to flood and water quality objectives for stormwater management. Specific design criteria which would allow these objectives to be achieved are not set out, but procedures that can assist in the development of criteria based on local watershed and receiving water conditions are described. While refinements will undoubtedly be needed, approaches to designing end-of-pipe facilities to prevent undesirable geomorphic changes are included. Approaches to protect groundwater and baseflow characteristics are also included although guidance on addressing potential trade-offs between groundwater quantity and quality is an additional challenge for the future. Little design guidance is available in Ontario on techniques to mitigate impacts on wetlands, however, developments from other jurisdictions may be transferable. The 2003 Manual promotes an integrated, treatment train approach to stormwater management that emphasizes prevention first, followed by lot-level and conveyance controls and finally, endof- pipe controls. Some information on better site design techniques is incorporated but in comparison to other jurisdictions, less emphasis has been placed on low-impact development strategies. Ontario's approach to design for water quality (suspended solids) control has evolved little. To complement the prevention and treatment train philosophy, the removal efficiency approach to sizing end-of-pipe facilities needs to be used in conjunction with effluent criteria and/or minimum requirements for source protection. Significant advancements in stormwater modelling over the last decade are not well reflected in the Manual; the limited discussion of modelling focusses on an event-based approach. Whether event or continuous modelling is utilized, Ontario practitioners will need guidance on adapting input data to account for the anticipated effects of climate change. Development of sound guidance on monitoring increasingly complex, multi-objective stormwater management systems and the ecosystems they are designed to protect will be critical to ensure that the knowledge gained from performance evaluations may continue to be utilized to refine the design and management of stormwater systems.

Storm Flow from First-Flush Precipitation in Stormwater Design

Regulations for mitigating nonpoint source pollution from urban areas often include a requirement for treatment of a first-flush depth of stormwater. When the stormwater treatment technology requires specification of a design flow rate, the first-flush depth must be related to a first-flush flow rate. This paper describes a methodology to determine the relation between accumulated storm depth and corresponding flow to a treatment device for small, urban watersheds. The approach uses the rational method under the assumption that the time-of-concentration is small. Intensity–frequency relations, expressed in the form of return periods and associated intensities, were determined using a partial duration frequency analysis of regionalized precipitation data. The results of the method can be used to determine the flow rate to a treatment device that will meet a specified return period for a first-flush depth. The method is demonstrated using 13 years of 15-min data from seven Massachusetts precipitation stations.

Discussion of “Runoff Capture and Delivery Curves for Storm-Water Quality Control Designs” by James C. Y. Guo and Ben Urbonas

Discussion of “Runoff Capture and Delivery Curves for Storm-Water Quality Control Designs” by James C. Y. Guo and Ben Urbonas

Runoff Capture and Delivery Curves for Storm-Water Quality Control Designs

A storm-water quality control system consists of trickle channels and water quality control basins (WQCB). To be economical, a WQCB is often designed to capture rainfall events smaller than extreme events. In current practice, the design rainfall statistics and runoff capture rates for sizing a WQCB have to be derived from the local long-term continuous rainfall record. Such a rainfall-runoff simulation process is lengthy and time-consuming. In this study, the analyses of 30- to 40-year continuous rainfall data recorded from seven metropolitan areas in the United States indicate that the frequency distribution of rainfall event-depths can be described by an exponential decay function. Applying the exponential distribution to a complete rainfall data series, the normalized runoff capture curve is derived in this study to describe the nonexceedance probability distribution of runoff depths. Similarly, the normalized runoff delivery curve is also developed to describe the nonexceedance probability distribution of runoff rates. These two curves provide necessary and important design information by which both the trickle channel and the WQCB can be sized on a consistent basis of overflow risk.

Geographic Information Systems, Decision Support Systems, and Urban Storm-Water Management

The application of geographic information system (GIS) technology to the field of urban storm-water modeling is reviewed. Then a GIS application in urban storm-water management is presented at a neighborhood scale. The neighborhood scale application includes a GIS, a database, a storm-water system design template, and an optimization capability for screening alternatives. The area and soil-type based Soil Conservation Service (SCS) method is used for calculating runoff from GIS information. Using economic analysis to compare the cost of controls, including the opportunity cost of land for land intensive controls, the optimal mix of best management practice (BMP) controls was found using linear programming. Finally, a single site example is presented illustrating the value of GIS tools to provide more complex on-site hydrologic analysis.