Stormwater Best Management Practices Research Articles

Effects of distributed and centralized stormwater best management practices and land cover on urban stream hydrology at the catchment scale

Summary Urban stormwater runoff remains an important issue that causes local and regional-scale water quantity and quality issues. Stormwater best management practices (BMPs) have been widely used to mitigate runoff issues, traditionally in a centralized manner; however, problems associated with urban hydrology have remained. An emerging trend is implementation of BMPs in a distributed manner (multi-BMP treatment trains located on the landscape and integrated with urban design), but little catchment-scale performance of these systems have been reported to date. Here, stream hydrologic data (March, 2011–September, 2012) are evaluated in four catchments located in the Chesapeake Bay watershed: one utilizing distributed stormwater BMPs, two utilizing centralized stormwater BMPs, and a forested catchment serving as a reference. Among urban catchments with similar land cover, geology and BMP design standards (i.e. 100-year event), but contrasting placement of stormwater BMPs, distributed BMPs resulted in: significantly greater estimated baseflow, a higher minimum precipitation threshold for stream response and maximum discharge increases, better maximum discharge control for small precipitation events, and reduced runoff volume during an extreme (1000-year) precipitation event compared to centralized BMPs. For all catchments, greater forest land cover and less impervious cover appeared to be more important drivers than stormwater BMP spatial pattern, and caused lower total, stormflow, and baseflow runoff volume; lower maximum discharge during typical precipitation events; and lower runoff volume during an extreme precipitation event. Analysis of hydrologic field data in this study suggests that both the spatial distribution of stormwater BMPs and land cover are important for management of urban stormwater runoff. In particular, catchment-wide application of distributed BMPs improved stream hydrology compared to centralized BMPs, but not enough to fully replicate forested catchment stream hydrology. Integrated planning of stormwater management, protected riparian buffers and forest land cover with suburban development in the distributed-BMP catchment enabled multi-purpose use of land that provided esthetic value and green-space, community gathering points, and wildlife habitat in addition to hydrologic stormwater treatment.

Minimization of cost, sediment load, and sensitivity to climate change in a watershed management application

One challenge of climate change adaptation is to design watershed-based stormwater management plans that meet current total maximum daily load targets and also take into consideration anticipated changes in future precipitation patterns. We present a multi-scale, multiobjective framework for generating a diverse family of stormwater best management practice (BMP) plans for entire watersheds. Each of these alternative BMP configurations are non-dominated by any other identified solution with respect to cost of the implementation of the management plan and sediment loading predicted at the outflow of the watershed; those solutions are then pruned with respect to dominance in sensitivity to predicted changes in precipitation patterns. We first use GIS data to automatically precompute a set of cost-optimal BMP configurations for each subwatershed, over its entire range of possible treatment levels. We then formulate each solution as a real-valued vector of treatment levels for the subwatersheds and employ a staged multiobjective optimization approach using differential evolution to generate sets of non-dominated solutions. Finally, selected solutions are mapped back to the corresponding preoptimized BMP configurations for each subwatershed. The integrated method is demonstrated on the Bartlett Brook mixed-used impaired watershed in South Burlington, VT, and patterns in BMP configurations along the non-dominated front are investigated. Watershed managers and other stakeholders could use this approach to assess the relative trade-offs of alternative stormwater BMP configurations.

Effects of Surface Area and Inflow on the Performance of Stormwater Best Management Practices with Uncertainty Analysis

The performance of stormwater best management practices (BMPs) is affected by BMP geometric and hydrologic factors. The objective of this study was to investigate the effect of BMP surface area and inflow on BMP performance using the k-C* model with uncertainty analysis. Observed total suspended solids (TSS) from detention basins and retention ponds data sets in the International Stormwater BMP Database were used to build and evaluate the model. Detention basins are regarded as dry ponds because they do not always have water, whereas retention ponds have a permanent pool and are considered wet ponds. In this study, Latin hypercube sampling (LHS) was applied to consider uncertainty in both influent event mean concentration (EMC), C(in), and the areal removal constant, k. The latter was estimated from the hydraulic loading rate, q, through use of a power function relationship. Results show that effluent EMC, C(out), decreased as inflow decreased and as BMP surface area increased in both detention basins and retention ponds. However, the change in C(out), depending on inflow and BMP surface area for detention basins, differed from the change in C(out) for retention ponds. Specifically, C(in) was more dominantly associated with the performance of the k-C* model of detention basins than were BMP surface area and inflow. For retention ponds, however, results suggest that BMP surface area and inflow both influenced changes in C(out) as well as C(in). These results suggest that sensitive factors in the performance of the k-C* model are limited to C(in) for detention basins, whereas BMP surface area, inflow, and C(in) are important for retention ponds.

Hydrologic Modeling of a Retention Irrigation System

AbstractUrbanized watersheds produce instantaneous response to rainfall, resulting in storm-water runoff exceeding the carrying capacity of drainage systems—the management of which is important to prevent flooding and erosion of streams. Management can be achieved using structural storm-water best management practices (BMPs). The city of Austin, Texas, envisioned a plan to mitigate future scenarios for flooding and erosion, resulting in the development and integration of storm-water BMP algorithms into the subhourly version of the soil and water assessment tool (SWAT) model. Algorithms were developed to simulate the physical processes governing the flow transport mechanisms through these BMPs. They were tested using a previously flow-calibrated watershed in the Austin, Texas, area. The retention irrigation (RI) system is one such BMP commonly found in Austin, Texas. This paper describes the development of a modeling tool for the RI system and its potential applications. From the test results obtained, it ...

Evaluation of pollutant loads from stormwater BMPs to receiving water using load frequency curves with uncertainty analysis

This study examined pollutant loads released to receiving water from a typical urban watershed in the Los Angeles (LA) Basin of California by applying a best management practice (BMP) performance model that includes uncertainty. This BMP performance model uses the k-C* model and incorporates uncertainty analysis and the first-order second-moment (FOSM) method to assess the effectiveness of BMPs for removing stormwater pollutants. Uncertainties were considered for the influent event mean concentration (EMC) and the aerial removal rate constant of the k-C* model. The storage treatment overflow and runoff model (STORM) was used to simulate the flow volume from watershed, the bypass flow volume and the flow volume that passes through the BMP. Detention basins and total suspended solids (TSS) were chosen as representatives of stormwater BMP and pollutant, respectively. This paper applies load frequency curves (LFCs), which replace the exceedance percentage with an exceedance frequency as an alternative to load duration curves (LDCs), to evaluate the effectiveness of BMPs. An evaluation method based on uncertainty analysis is suggested because it applies a water quality standard exceedance based on frequency and magnitude. As a result, the incorporation of uncertainty in the estimates of pollutant loads can assist stormwater managers in determining the degree of total daily maximum load (TMDL) compliance that could be expected from a given BMP in a watershed.

Impact of Storm Water Recharge Practices on Boston Groundwater Elevations

Over the past century, the City of Boston has periodically experienced a decline in groundwater elevations and the associated deterioration of untreated wood piles, which support building foundations. To combat declining water tables, Boston enacted a groundwater conservation overlay district enforced by city zoning boards to require storm water recharge practices for any activity that triggers the zoning bylaw. In Boston, recharge to the water table results from the infiltration of rainfall and snowmelt, leakage from water mains, and recharge from artificial systems. Increased mitigation activities to reduce unaccounted-for water have reduced leakage from water mains in the city. Given the high percentage of impervious cover in Boston, the remaining sources of recharge are primarily artificial systems, including pump and infiltrate systems and storm water recharge best management practices (BMPs). The primary objective of this research was to exploit existing information on groundwater elevations and recharge practices to quantify the effect of the required recharge BMPs on the behavior of groundwater elevations in the Back Bay region of Boston. Regional multivariate regression models were developed to determine the potential effects of recharge BMPs on observed groundwater elevations. The literature review revealed several analogous multivariate linear regression studies, none which focused on behavior of stormwater BMPs. The model reveals that the installation of recharge BMPs has a small but highly statistically significant positive effect on groundwater elevations in the Back Bay with the effect being proportional to their capacity and inversely proportional to their distance from the location of interest. The resulting model can be used to predict the effect on average groundwater elevations at a particular location resulting from the installation of a recharge BMP or a set of such BMPs of a particular capacity at a particular distance from the location of interest.

Stormwater BMP treatment performance variability for sediment and heavy metals

Performance-based stormwater best management practice (BMP) selection should match appropriate technologies with site water quality concerns and consider the ability to meet water quality standards. Empirically derived frequency analysis of effluent flow-weighted composite event mean concentrations (EMCs) for sites in the International BMP Database are presented for total suspended solids, and total and dissolved zinc and copper for dry detention basins, retention basins, wetland basins, media filters, grassed swales, bioretention, and permeable pavement. Performance characterization amongst BMPs using the probability plots is also compared to typical percent removal type assessment. No single device emerges as providing the best treatment across all water quality parameters considered. Detention basins provide the least water quality protection amongst all devices, and will not likely satisfy the typical goal of 75% TSS removal. Retention ponds can meet the 75% objective only when median percent removal is considered, but effluent TSS EMCs are approximately twice the level as compared to bioretention cells and grassed swales for the majority of events. Most BMPs are able to meet US EPA marine water quality discharge criteria for zinc, and many are able to meet the more stringent ANZECC threshold for 95% species protection. Copper is problematic for all BMPs with respect to water quality criteria. Resurfacing with permeable pavement could prevent up to 2/3 of the contaminant concentrations from typical urban source areas.

Special Issue on Urban Storm-Water Management in the 21st Century

As the practice of storm-water management evolves, so has our understanding of the tools. As we move away from a myopic flood control perspective, new tools to include what we now call green infrastructure best management practices (BMPs) were developed. Green roofs, rain gardens, and porous pavements appeared, with much of the design elements based on reasonable estimates of performance, thus the term “best.” Now we as a profession are moving toward a more engineered approach, with designs based on scientific knowledge of the processes, from soil physics and chemistry to hydrology and hydraulics. Soon it may be time to retire BMPs and move forward with the term “storm-water control measures,” as recommended by the National Academies authors of Urban Stormwater in the United States (National Research Council 2008). This issue of the Journal of Irrigation and Drainage Engineering is devoted to this evolving field of storm-water sustainability, and the effort to predict performance of our storm-water control measures. The 10 papers in this special issue reflect this evolution. Papers range from evaluating the concentration of effluent scoured from catch basins to cost-estimation tools, plus the inclusion of green-infrastructure tools within the International Stormwater BMP Database. Green and stone roofs are represented as are level spreaders. Bioretention/bioinfiltration rain gardens, however, received the most attention with papers on media depth, phosphorus removal, process modeling, mounding, and fines accumulation. This collection truly demonstrates our increasing knowledge base. This effort is a result of collaboration between the Stormwater Infrastructure Committee and Urban Water Resources Research Council, together with the Journal of Irrigation and Drainage Engineering Publications Committee. Conference proceedings from recent Environmental and Water Resources Institute (EWRI) congresses and low-impact development (LID) conferences were reviewed, and a select group of authors was invited to expand and revise their work. These papers passed through the standard journal peer-review process. We hope that this set of papers is of use to the profession. We would like to thank all the contributing authors, the reviewers, and William Ritter, as editor, for their efforts in this special issue.

Development of Sub-Daily Erosion and Sediment Transport Algorithms for SWAT

New Soil and Water Assessment Tool (SWAT) algorithms for simulation of stormwater best management practices (BMPs) such as detention basins, wet ponds, sedimentation filtration ponds, and retention irrigation systems are under development for modeling small/urban watersheds. Modeling stormwater BMPs often requires time steps as small as minutes to realistically capture the instantaneous flow and sediment load coming from upland areas. SWAT2005 uses the Modified Universal Soil Loss Equation (MUSLE) for modeling upland erosion and sediment load. The MUSLE model is an empirical soil loss equation, which was formulated based on field observations rather than theoretically derived relationships to predict long-term average soil loss. This article presents modified physically based erosion models in SWAT for seamless modeling of erosion processes with the recently developed sub-hourly flow models. In the new algorithms, splash erosion is calculated based on the kinetic energy delivered by raindrops, adapted from the European Soil Erosion Model, and overland flow erosion is estimated using a physically based equation adapted from the Areal Nonpoint-Source Watershed Environment Response Simulation (ANSWERS) model. The Yang model and the Brownlie model were also modified for in-stream sediment routing. The SWAT model with the modified sub-daily sediment algorithms was calibrated and validated each for a one-year period at 15 min intervals with measured data from the USDA-ARS Riesel watersheds in Texas. Results show that SWAT with the sub-daily algorithms performed as well or better in terms of sediment yield prediction than SWAT with the current daily output structure. In addition, SWAT (sub-daily) was able to adequately represent the timing, peak, and duration of sediment transport events. Thus, this initial evaluation indicates that the new sub-daily flow and sediment structure in SWAT is a promising tool for water quality assessment studies in small watersheds or urban watersheds where sub-daily process are so important to quantify.

Best Management Practices for Stormwater Management in the Desert Southwest

Abstract:Despite several decades of experience with stormwater Best Management Practices (BMPs) in the United States, the application of such approaches in the Desert Southwest region has not received adequate attention. One reason for this shortcoming could be the general perception of the insignificance of BMPs in a region with little annual precipitation. However, the Desert Southwest still experiences relatively high rainfall intensity and runoff from rainfall. Sparse vegetation, steep topography, complex soils, unique geology, and rapid land development all contribute increase runoff response. Since the Desert Southwest hosts a large and rapidly growing population, stormwater BMPs are important for protecting the quality and quantity of scarce receiving surface and ground waters. The hydrometereological characteristics of intense short‐term precipitation, large inter‐storm duration, and smaller annual volumes of rainfall and the region's watershed characteristics are unique; the design of regional stormwater BMPs should consider these characteristics. Also, there is a need for more specific design guidance for implementing general approaches for adapting stormwater BMPs from humid regions to arid settings.

Evaluation of stormwater BMPs for implementing industrial stormwater permitting strategy

This study assesses the performance of stormwater best management practices (BMPs) in industrial sectors and their effluent quality to facilitate the development of technology-based numerical effluent criteria. Generally, retention ponds outperform other BMP types for reducing total suspended solids, and media filter and wetland basins outperform other BMPs for metal removal. Detention basins were not effective in reducing stormwater pollution although they can retain the stormwater before entering surface waters. However, many BMPs show high variability of influent and effluent concentrations and no significant difference between them, which makes it difficult to determine the effectiveness of the BMP. In some cases, low influent concentrations govern the distribution of effluent concentrations and effluent concentrations are often greater than inflow concentrations. The analysis results can be used to assist in the developing a watershed based multisector industrial stormwater general permit to ensure compliance with total maximum daily loads. The results also suggest the need for additional monitoring data.

The Runoff Reduction Method

Abstract:The Runoff Reduction Method (RRM) provides an innovative approach to crediting the total performance of stormwater best management practices (BMPs). Total BMP performance refers to the pollutant removal and runoff volume reduction capabilities. The RRM tracks the implementation of stormwater BMPs, including Low Impact Development (LID) strategies such as permeable pavement, rainwater harvesting, downspout disconnection, soil amendments, etc., and credits the appropriate runoff volume reduction, pollutant concentration reduction, or both towards compliance with stormwater quality and quantity requirements. By providing a mechanism to credit the volume reduction associated with these LID strategies the RRM also documents an allowable reduction of the overall size and footprint of structural detention practices, thereby providing an economic incentive for the development community to implement LID providing a better overall solution for minimizing the impact of development on the hydrologic cycle.

Performance Modeling of Storm Water Best Management Practices with Uncertainty Analysis

The performance of storm water best management practices (BMPs) contains many uncertainties that make predicting BMP performance difficult. The objective of this study is to build a BMP performance model that incorporates uncertainty analysis and to evaluate this model using observed total suspended solids (TSS) from detention basin data sets in the International Stormwater BMP Database. The representative storage-treatment performance model, the k-C* model, was chosen to represent BMP performance. Its input parameters, influent event mean concentration (EMC) (Cin), and the areal removal rate constant (k) are considered with the uncertainty analysis. To estimate the variance associated with k, the prediction interval method is applied to the linear regression equation relating hydraulic loading rate (q) to k. To estimate the variance of Cin, observed Cin data in the BMP database are used. This study assumes that both Cin and k can be represented by lognormal distributions. The probability density function...

Cost-effectiveness analysis of stormwater best management practices (BMPs) in urban watersheds

This study demonstrates a cost-effectiveness analysis of stormwater BMPs to answer questions, such as what type to place and how large it should be. Cost-effective analysis showed that for the basin considered, a porous pavement was the most effective means of controling runoff, which was able to bring the peak runoff down to the predevelopment level with the least budget. A storage basin was the second best, which was able to bring the peak runoff down to the predeveloped conditions, but with a higher budget. The effectiveness of a green roof in reducing the peak runoff plateaued beyond a certain budget, and was unable to bring the peak runoff down to the predeveloped level, regardless of cost. It is thought that a porous pavement would be a cost-effective BMP in a severely urbanized setting.

Integration of Low-Impact Development into the International Stormwater BMP Database

Low impact development (LID) strategies are being encouraged in many communities as an approach to reduce potential adverse impacts of development on receiving streams. Many questions exist regarding how well various LID strategies perform in different settings, just as similar questions have been raised regarding performance of traditional stormwater best management practices (BMPs). Whereas historical focus on BMP performance has been water quality concentrations or loads, characterization of volume reduction benefits for both conventional and LID practices is increasingly an objective of researchers and stormwater managers. More than a decade ago, Urban Water Resources Research Council (UWRRC) members worked to develop a set of standardized monitoring and reporting protocols for traditional BMPs and to establish a master database for the purpose of evaluating BMP performance and the factors affecting performance. This effort culminated in the International Stormwater BMP Database (www.bmpdatabase.org), which contains data for more than 360 BMPs and continues to operate as a clearinghouse for stormwater BMP data and performance analyses. During 2008–2009, the International Stormwater BMP Database project expanded to better integrate LID into the database and develop a set of metrics that can be used to characterize BMP performance with regard to surface runoff volume reduction. This paper provides a condensed overview and progress report on the LID-focused effort, including the following topics: (1) monitoring guidance for LID at the overall site development level, (2) an overview of recent changes to the International Stormwater BMP Database to better accommodate LID studies, (3) a summary of LID studies currently included in the database, and (4) a proposed approach for evaluating performance of LID studies with regard to reducing surface runoff volumes.

Variability in adsorptive phosphorus removal by structural stormwater best management practices

Various best management practices (BMPs) utilizing sorption processes (SP) have demonstrated effectiveness for phosphorus (P) management in stormwater. However, the widespread use of these BMPs in urban areas has been limited by large land requirements and limited P removal capacity. Central to this study is the development of the urban wetland filter (UWF), a concept intended to overcome these limitations and provide a low-cost, easily implemented BMP that can meet urban P-management goals. Performance variation along with finite sorption capacity has limited the reliability of SP as a primary removal strategy. However, if variability were better understood and capacity made renewable, sorption of P to substrates could provide the option of a more rapid and (with less required retention time) more space-efficient sustainable removal strategy than biological uptake. The goal of this study was to identify and model major sources of variability in P removal by sorption, enabling better prediction and optimization of sorption performance and ultimately the development of a small-footprint stormwater BMP with efficient P removal ability. Experiments were conducted in bench-scale reactors with an iron-oxide sand substrate. Results included a physical-process model developed by considering the thermodynamic and kinetic properties of SP. Significant sources of variability included, by order of importance, magnitude of a solution/substrate concentration gradient, length of the “antecedent dry period” between loadings, and pH. Most importantly, results indicate the critical importance of a thermodynamic gradient between solution P and previously adsorbed P to achieve continued removal.

Establishing Storm-Water BMP Evaluation Metrics Based upon Ambient Water Quality Associated with Benthic Macroinvertebrate Populations

Storm-water experts agree that the currently used best management practice (BMP) percent removal methodology metric has many flaws, and some have suggested using a BMP effluent concentration metric. This case study examines establishing an effluent target concentration for BMPs that relates to the health of macroinvertebrates in the receiving water. In North Carolina, 193 ambient water quality monitoring stations were paired with benthic macroinvertebrate health ratings collected in very close proximity. Water quality for the sites ranged from excellent to poor and was divided into three distinct ecoregions: Mountain, Piedmont, and Coastal. Statistically significant relationships were found in one or more ecoregions for dissolved oxygen, fecal coliform, NH3 , NO2−3 − N , total Kjeldahl nitrogen, total nitrogen (TN), and total phosphorus (TP). BMPs can then be selected and designed to meet these target effluent concentrations. Based upon this research, a development, and therefore set of BMPs, in Piedmont ...

Thermal Reduction by an Underground Storm-Water Detention System

Increases in stream temperatures by heated storm-water runoff from impervious surfaces are a serious environmental problem. An underground detention with slow-release facility is a versatile storm-water best management practice (BMP) for buffering high flows. Temperature reductions in underground storm-water storage BMPs, however, have not been quantified. A field study on an underground detention BMP located in Maryland was undertaken to characterize its effect on storm-water runoff temperatures. In colder months, when the runoff temperature ranged from 5 to 15°C , small or no temperature change was observed. Runoff produced during summer storm events, however, with event mean temperatures over 20°C , exhibited mean temperature reductions of 1.6°C through the BMP. While statistically significant, the reductions were not sufficient to cool the summer runoff discharges below the Maryland Class III temperature standard ( 20°C ) 100% of the time. The results indicate that underground facilities can moderate ...

Application of the Analytical Hierarchical Process for Improved Selection of Storm-Water BMPs

Engineers and planners responsible for the selection and design of storm-water best management practices (BMPs) face a formidable array of practices and techniques for managing the quality of urban runoff. Primary factors affecting the choice of BMP invariably include the performance capability of a given class of BMPs and the new impervious cover fraction arising from development projects. We introduce the analytical hierarchal process (AHP) as an analytical framework for BMP selection, through priority ranking of storm water control objectives and BMP performance metrics. Using the AHP, a BMP priority ranking is accomplished through the construction of pairwise relative rankings of the selection criteria and then of the BMPs themselves against the respective selection criteria. The use of normalized ranking vectors, obtained through eigenvector approximation, is employed to provide a final ranking of BMP choices that then can be carefully reviewed by the design engineer. Two BMP selection applications a...

Simulation of the Performance of a Storm-Water BMP

Vegetated storage-infiltration best management practices (BMPs) have become an increasingly popular means of attenuating and treating runoff from developed land. However, the hydrologic and pollutant removal performances of these facilities can be highly variable. A mathematical model of an idealized BMP was developed in order to quantify the impact of variable hydrologic and pollutant concentration input on BMP performance by simulating the treatment performance of the model system during 1,250 non-steady-state storm events generated based on historic Maryland rainfall data. The model BMP was effective in attenuating volume (42% total volume reduction) and peak flow (median peak output to peak input flow ratio was 0.058). The simulated mean effluent pollutant event mean concentration was much less than the influent (0.284 compared with 1.51 mg/L) and the overall mass load reduction was 92%. However, the performance parameters demonstrated significant variability. Consequently, the results suggest a need to incorporate into BMP performance guidelines the impact of the variable influent hydrologic and pollutant concentration characteristics. Emphasis should be placed on discharge water quality and statistical distributions rather than on single-percent removal values.