Encouraging conservation design principles in layout design for new subdivisions is very effective in preserving the natural state of a watershed. A clustered development rather than the traditional individual plots and set back style of development with large passive open spaces is very effective. Arendt (1996), in his book Conservation Design for Subdivisions : A practical guide to create open space networks, discusses various designs and the advantages of conservation design over traditional layout designs. More information can also be found at http://www.webcom.com/~pcj/articles/are015.html

A layout design based on conservation design principles has several long and short-term cost benefits. All land uses, in particular residential areas with green corridors around and large open spaces provide several amenities such as attractive views, convenient recreation oppurtunities and preservation of natural areas. These added benefits are valued by people. Studies and surveys have shown that property values correlate significantly with proximity to parks and trails. People are willing to pay more to be close to such amenities.

Reduced driveways, paved pedestrian paths, road, sewer and drain lengths also add to the reduction of construction and maintainence costs.

Hartford County, Maryland’s zoning ordinance encourages enterprising design solutions for layouts by allowing developers to increase the residential density to the next higher class if more than 30% of the site is designated a natural resource district. The purpose of this is to promote the preservation of natural environmental features such as wetlands, streams and steep slopes (Salvesen, 1990)

The example to the right illustrates a proposed development site, which is partially covered with wetlands. A local planning and engineering consulting office developed a site plan that accommodates the site’s constraints and takes advantage of the special natural resource district provision in the zoning ordinance. The proposal suggests a clustered development of townhouses on the higher grounds leaving the wetlands virtually untouched. By doing this, large portions of the site are left as passive open spaces, stream crossings are reduced from five in the traditional layout design to three, and the clustered development leads to a dramatic cut in the cost of providing utilities and services. In addition, draining and filling of wetlands is reduced to a minimum (Salvesen, 1990)