STORMWATER HYDROLOGY AND QUALITY - Low Impact Development and Sustainable Stormwater Management - page 38

Figure 2-4 First-order streams begin as seeps and springs and are the most vulnerable
element of the hydrologic cycle.
This complex web of life that begins in small surface streams that ultimately
flow into and form mighty rivers and estuaries is an important consideration in
the land development process. When we recognize our “watershed address,” and
the sensitivity of the land-water system in which we plan to develop, we will
better understand the interdependency between land and water resources.
During our brief three centuries in North America, we have literally moved
land development from the mouths of major river systems to the source of those
systems in the headwaters, where countless first-order streams sustain the entire
drainage system. The interdependency is obvious if we think carefully about
where we build, but past experience indicates that this concern has not been
given voice until very recently.
2.3 STORMWATER VOLUME
Once the water balance has been estimated for a given site, the guidelines for sus-
taining this balance must be established. These technical guidelines evolve into
specific design criteria that can be applied to a broad spectrum of stormwater man-
agement solutions, commonly referred to as best management practices (BMPs),
which have evolved as the tools for LID. This topic presents stormwater manage-
ment principles and recommends site control guidelines for volume, water quality,
and rate. These guidelines are proposed as the basis for municipal stormwater reg-
ulation, and offer guidance for municipalities desiring to improve their stormwater
management programs. Some state laws and regulations manage stormwater
directly at the state level, while some state-level management occurs through
programs such as NPDES Phase II permitting, or the MS4 program, but whatever
the regulatory format, the first step is to “set the bar” for our LID strategies.