CASE STUDIES - Low Impact Development and Sustainable Stormwater Management - page 208

an outlet that detained runoff and mitigated the peak flow for a sufficient period
to avoid downstream bank erosion. A full set of design guidelines evolved and
were promulgated, usually at the local or county level rather than being incor-
porated in state or federal water quality regulations, in order to influence the
land development process in concert with zoning and development regulations.
The suburban development explosion that was taking place throughout the nation
was suddenly faced with a technical requirement to control runoff, a practice that
spread rapidly to every community.
Within an incredibly short period of a few years, every new land development
project included a detention basin, following sizing and performance criteria
recommended by the SCS and tailored in each community to fit local concerns and
practices. It would be accurate to say that the detention basin became the national
standard for stormwater management in the land development process, and has
continued to serve as such for the past 35 years. When the technical community of
water quality experts began to make the connection between sediment pollution
as the transport mechanism for phosphorus and other pollutants, and the root
cause of eutrophication of almost every freshwater body in developed regions,
the need to control (or prevent) this pollutant load from the landscape reaching
these surface waters became critical.
Even as hundreds of thousands of detention basins were constructed dur-
ing the 1970s and 1980s, it became apparent that this measure, in itself, was
insufficient to offset the full impact of the land development process on water
resources. Much more needed to be done in the actual site construction process, by
reducing the amount of land disturbed, reducing the amount of earthwork, config-
uring dwelling units in closer patterns, and not simply counting on the detention
basin to capture runoff and prevent sediment pollution. During the 1980s, various
investigators (including the present author) advocated that the primary technical
solution to preventing increased runoff from developed landscapes was to focus
on volume control rather than mitigating the rate of runoff as accomplished by
detention designs. Despite the initial rejection of this concept, various technolo-
gies using innovative methods and materials were constructed. These included
porous pavements (first tested in the 1970s and finding broad application in the
1980s), vegetated roofs (derived from the German experience of the late 1970s
and 1980s and brought to the United States in the 1990s), and vegetative systems
that were designed in the 1980s as “vegetated infiltration beds” but caught on as
“rain gardens” in the 1990s. Other technologies, especially capture-reuse sys-
tems, were used in other countries but met with resistance in the United States,
based largely on existing water supply infrastructure (and ownership), fears of
supply contamination, and regulatory obstacles.
The case studies included here are divided into three categories: manuals, basin
plans or models, and constructed LID projects. While the basic issue of runoff-
transported pollution is the central concern throughout, the popular acronym has
evolved and changed over the 35-year period, from non-point Source (NPS)
control to best management practices (BMPs) to low-impact development (LID).
The more recent term living building goes beyond the site design issues and has