Site Planning and Design Concepts

Effective site planning is largely based on the following key principle:

Preserve predevelopment hydrology. The natural systems in place in an undeveloped setting are in balance. A large portion of precipitation infiltrates into the ground to recharge aquifers and provide base flow for streams. In contrast, highly developed sites capture and channel a much larger portion of precipitation and direct it to surface water bodies, where it causes a variety of impacts.

Proper site planning is a critical first step towards reducing the impacts of development on water resources. The following concepts are based on the guidance provided in the Low Impact Development manual (Prince George's County, 1999:

Designing the Development to fit the Terrain
Soil disturbance is reduced when a development is designed to fit in to the existing terrain. Placement of roads parallel to contours makes the installation of natural drainage ways easier.

Limiting Land Disturbance Activities
By limiting land disturbance only to those areas absolutely necessary for construction, the intact natural systems can be preserved. This is more difficult and less practical on smaller lots in more urbanized areas.

Reducing or Disconnecting Impervious Areas
Impervious surfaces are a necessary component of development, however there are options to reduce to "connectedness" of these surfaces to the stormwater system. See section 4.3 of the CT Stormwater Quality Manual for specific techniques to disconnect impervious surfaces.

Preserving and Utilizing Natural Drainage Systems
Traditional stormwater design seeks to collect, concentrate and convey stormwater offsite. The LID approach advocates the use of vegetated systems, both existing and newly constructed, to keep runoff on the site.

Providing Setbacks and Vegetated Buffers
Buffers help to reduce pollutant transport to surface water bodies both during and after construction. They also provide benefits to wildlife.

Minimizing the Creation of Steep Slopes
Disturbance of vegetation on steep slopes creates a high potential for erosion, and pollutant transport to surface waters. Slopes greater than 10% generally should be stabilized.

Maintaining Pre-Development Vegetation
Intact vegetation helps to infiltrate and evapotranspire rainfall, which reduces the potential for runoff from the site. Erosion potential is also reduced.

For more information, visit the following section of the CT Stormwater Quality Manual:

Chapter 4, Section 4.2

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