(reprinted from the Planning Manual as included within the Integrated Stormwater Management (“iSWM”) library of manuals as published by the North Central Texas Council of Governments (NCTCOG)
The following narrative is presented as a preface to reading the Planning Manual, which is the first manual as contained within the set of manuals generally referred to as ISWM. For further reading, click on the link at the end of this preface to download the Planning manual from our site.
The first step in addressing stormwater management begins with the site planning and design process.
Development projects can be designed to reduce their impact on watersheds when careful efforts are made to conserve natural areas, reduce impervious cover, and better integrate stormwater treatment. By implementing a combination of these nonstructural approaches collectively known as integrated Site Design Practices, it is possible to reduce the amount of runoff and pollutants that are generated from a site and provide for some nonstructural on-site treatment and control of runoff. The goals of integrated site design include:
- Managing stormwater (quantity and quality) as close to the point of origin as possible and minimizing collection and conveyance
- Preventing stormwater impacts rather than mitigating them
- Utilizing simple, nonstructural methods for stormwater management that are lower cost and lower maintenance than structural controls
- Creating a multifunctional landscape
- Using hydrology as a framework for site design
- Reducing the peak runoff rates and volumes, therefore, reducing the size and cost of drainage infrastructure and structural stormwater controls
Integrated site design for stormwater management includes a number of site design techniques such as preserving natural features and resources, effectively laying out the site elements to reduce impact, reducing the amount of impervious surfaces, and utilizing natural features on the site for stormwater management. The aim is to reduce the environmental impact “footprint” of the site while retaining and enhancing the owner/developer’s purpose and vision for the site. Many of the integrated Site Design Practices can reduce the cost of infrastructure while maintaining or even increasing the value of the property.
Reduction of adverse stormwater runoff impacts through the use of integrated site design should be the first consideration of the design engineer. Operationally, economically, and aesthetically, the use of integrated Site Design Practices offers significant benefits over treating and controlling runoff downstream. Therefore, all opportunities for using these methods should be explored and all options exhausted before considering structural stormwater controls.
The reduction in runoff and pollutants using integrated site design can reduce the required runoff peak and volumes that need to be conveyed and controlled on a site and, therefore, the size and cost of necessary drainage infrastructure and structural stormwater controls. In some cases, the use of integrated Site Design Practices may eliminate the need for structural controls entirely. Hence, integrated Site Design Practices can be viewed as both a water quantity and water quality management tool.
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