An Overview of Stormwater Management

| April 27, 2018

A green roof planting

by Jane L. Didona

When only 1% of the world’s water is available for human consumption, it is imperative that this important resource is protected. Unfortunately, until the 1960s, water was not considered a resource. The historic disregard for our lakes, rivers, and streams, culminated in a legal battle against Con Edison’s proposal to destroy Storm King Mountain on the Hudson River. The language of this litigation became the foundation for the 1972 Clean Water Act.

Regulations for point source pollution had only a 20% improvement of the recreational waterways, and therefore amendments were made to the legislation to include non-point pollution including stormwater runoff. As a site becomes more impervious, the potential is for more water to leave the site carrying pollutants into streams, lakes, and oceans. The treatment of runoff as a source of pollution has become a major concern for federal, state, and local regulators.

A rain garden

Many stormwater treatment practices have a visual impact on the site. A 1995 EPA study determined that an artfully designed stormwater management structure can lead to increased marketability and property values. This is where a landscape architect can contribute to the stormwater management design process.

The first step for appropriate stormwater management is to site plan using a low-impact development model, which includes working with the site’s natural resources to minimize earthwork, steep slopes, and impervious surfaces, while preserving existing vegetation and the current drainage patterns.

The next step is to incorporate stormwater best management practices (BMPs) as tools that make up a treatment plan for quantity and quality of stormwater. Many of these BMPs are also design elements that enhance biodiversity and beauty of the site. The following list outlines the more common visual BMPs:

  • The rain garden is a very effective microscale practice that allows for the treatment and infiltration of runoff typically used to mitigate driveway and roof runoff. The native plants used in a rain garden provide seasonal interest and habitat. Although not every site is appropriate for a rain garden, it is an inexpensive method for handling runoff that adds beauty and therefore marketability to the site.
  • Permeable pavers are another method that can add to the beauty to the site. Asphalt is impervious and generally has a negative visual impact. Permeable pavers treat the stormwater at the source and become a visual asset to the site. In our experience, there is significantly less winter icing and no issue with handling the runoff if appropriately designed and installed.
  • Water catchment is an ancient method to collect runoff, specifically roof runoff. Stormwater is collected into a cistern or rain barrel for use in irrigation and/or fountains. Quite often the rain barrel becomes a decorative sculptural piece in the landscape.
  • Riparian buffers are vegetated areas that reduce the velocity of the runoff to allow for some infiltration and improve the water quality before the runoff drains into a wetland or water course.
  • Green roofs are planted roofs usually (but not necessarily) of flat buildings that utilize roof runoff in watering the plants. There are two major types of green roof: intensive and extensive. Intensive green roofs are gardens that can include human interaction. An extensive green roof is a vegetated roof that mitigates storm water runoff and further insulates the structure from heat/cooling loss.

A rain fountain fed by cistern

These are just some of the many practices that can be used to create a multi-use, bio-diverse, and aesthetic stormwater management plan. It is important to note that no two sites are alike, therefore each site, due to its soils, topography, and drainage patterns, will require its own unique plan. The goal of the plan is to treat the stormwater as well as to create a nurturing, thriving place that enhances the human experience and balances the natural environment. A landscape architect trained in the planning, design, and implementation of these practices can provide that level of design and therefore is an important member of the stormwater management planning team.

Jane L. Didona, PLA, ASLA, Didona Associates Landscape Architects, Inc.

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