About This Reference

This site provides a comprehensive technical reference for stormwater management practitioners, municipal staff, engineers, planners, and watershed managers. It offers a collection of design tools, guidance documents, and analytical frameworks to support the development and implementation of effective stormwater and watershed protection programs. The resources cover a wide spectrum of topics, from the design of individual best management practices (BMPs) to watershed-scale assessment and planning.

The content is organized to provide practical assistance for common challenges, such as selecting and designing appropriate stormwater controls, developing local ordinances, and establishing pollution prevention initiatives. The material is intended to be a functional resource for professionals seeking detailed engineering criteria, performance data, and regulatory templates.

What This Reference Covers

The information presented is structured around the core principles of watershed protection, addressing the impacts of urbanization on water resources through a multi-faceted approach. This includes guidance on structural stormwater controls, non-structural pollution prevention, and integrated site design techniques that reduce impervious cover and preserve natural hydrology.

A central theme is the application of better site design, a collection of development strategies that minimize the generation of stormwater runoff. These techniques focus on conserving natural areas, reducing impervious surfaces, and using the landscape to manage rainfall where it falls. By integrating stormwater management early in the design process, these methods can reduce the need for and size of conventional, end-of-pipe treatment facilities.

For runoff that requires treatment, this reference provides extensive information on a wide array of structural stormwater BMPs. These practices range from infiltration and bioretention systems to stormwater ponds and wetlands. The guidance addresses the selection, design, construction, and maintenance of these practices to achieve specific water quality and quantity control objectives. Complementing structural controls are non-structural pollution prevention strategies. These source-control measures aim to reduce the introduction of pollutants into the environment through operational practices like street sweeping, material management, and public education.

Tools and Calculators

A key feature of this resource is a suite of interactive tools designed to assist with analysis and design tasks. These tools provide a direct method for applying established engineering principles to specific project scenarios.

The online calculators offer a streamlined approach to common design computations. These include calculators for preliminary sizing of a stormwater pond, designing a dry swale, and estimating runoff and pollutant loads using the Simple Method. These tools are intended to support conceptual design and preliminary sizing efforts.

The BMP Selector is an interactive utility that helps users identify suitable stormwater management practices based on specific site constraints, land use, and treatment goals. By filtering options according to factors like soil type, drainage area, and desired pollutant removal, users can narrow the field of potential BMPs for a given project.

For detailed performance analysis, the Pollutant Removal Database compiles data from numerous technical studies on the effectiveness of various stormwater BMPs. This searchable database allows users to review documented removal rates for pollutants such as nitrogen, phosphorus, and suspended solids, providing a basis for practice selection and performance expectations.

At the watershed scale, two analytical frameworks are provided. The Impervious Cover Model offers a method for diagnosing watershed health and predicting how stream quality may change with development. The Watershed Treatment Model is a planning tool for estimating the cumulative effect of multiple BMPs and restoration practices across a watershed, allowing for the evaluation of different management scenarios.

Reference Material for Local Programs

This site contains a library of documents intended to support the development of local government stormwater and watershed management programs. These resources provide foundational material that can be adapted to meet specific jurisdictional needs.

The Model Ordinance Library contains a collection of adaptable legal frameworks for communities seeking to establish or update local regulations. The collection includes templates for comprehensive stormwater management ordinances, as well as specific ordinances addressing erosion and sediment control, stream buffers, illicit discharge detection, and other critical program elements. Each model ordinance serves as a starting point, providing structured language that can be customized to local legal and environmental contexts.

The Design Manual section presents a comprehensive collection of stormwater engineering criteria and guidance. Organized into distinct chapters, it covers topics from hydrologic analysis and practice selection to detailed design specifications for a full range of stormwater BMPs. This material can be used to supplement an existing manual or serve as the technical basis for a new one.

To assist with program terminology and communication, an extensive Glossary defines the key terms used in stormwater management and watershed science. This ensures a common understanding of technical concepts for engineers, planners, and public officials.

Sources and Methodology

The design guidance and technical criteria presented throughout this reference reflect widely adopted practices from state and municipal stormwater manuals across the United States. The information is synthesized from established engineering literature and regulatory precedents to provide a reliable basis for planning and design.

Quantitative data, particularly the performance figures in the Pollutant Removal Database and other data tables, are drawn from and cite the original peer-reviewed studies, government reports, and technical manuals from which they were obtained. This practice of direct citation allows users to consult the source literature for additional context and methodological detail.