LAND AS THE RESOURCE - Low Impact Development and Sustainable Stormwater Management - page 57

3.2 SUSTAINABLE SITE DESIGN
The process of sustainable site design begins by distinguishing the location of the
proposed site, with an initial classification as “undeveloped” or “redeveloped.”
In most situations this distinction is easy, with the cultivated or fallow field
situated well beyond the town center contrasted with redevelopment in a blighted
urban center, although not all situations fit easily in one class or the other. The
more important distinction is the presence or availability of utility infrastructure,
beginning with road access but also considering water, sewer, and power service,
as well as communications. For commercial land uses, the market is determined
by the highway connections, their proximity to population centers, and their
economic buying capacity.
LID is intended to deal with both land development and redevelopment situa-
tions, changing the way we build or rebuild our communities. In this chapter we
examine the set of concepts and processes that can begin to restore and sustain
the land resources affected by the new land development practices of the past
half century, as well as the rebuilding of our cities, a work in progress across the
country. The chapters that follow describe specific LID methods and materials,
both nonstructural (preventive) and structural, that can be applied to any given
site design throughout the country, with consideration of the natural constraints
and local hydrology.
3.3 WATERSHED SETTING AND PHYSICAL CONTEXT
Most land development plans are carefully fit within a given parcel, with the
building program framed around what is allowed by local land use regulation
and the accessibility of the site. Our current paradigm of development is driven
by the existing roadway network and usually fails to consider the regional context,
especially the hydrologic setting, or watershed. Since the roadway infrastructure
is usually the prime determinant in parcel selection, any reference to hydrologic
boundaries, such as ridgelines, is unheard of in the current development market.
For this reason alone, sustainable development requires a new perspective. The
site design solutions possible will be very dependent on where we are situated
within a given watershed, regardless of the relative size. Generally speaking, the
headwaters of a given watershed are less likely to support large alterations in
topography (grading), more likely to affect the most sensitive elements of the
surface drainage system (first-order streams), and result in greater removal of
existing vegetation, since the steeper slopes have generally deterred cultivation
in historic landscapes.
As the scale of watersheds increase to larger and larger aggregations such as
major river basins (the Mississippi or Colorado), estuaries (the Chesapeake or
Sacramento) or lacustrine systems such as the Great Lakes, the watershed setting
requires a broader perspective. While larger systems usually share a common