Regulated Rivers - Hydro-Environmental Analysis: Freshwater Environments - page 79

river ecology has not been a consideration in that design and optimization. To do so in some cases
will require changes not only in attitudes, but also in the laws, regulations, codes, ordinances, and
other rules that control and dictate river engineering design and management. For example, the rule
curve by which a reservoir is operated may not have included isheries management in the reser-
voir and its tailwaters during the rule curve development. Therefore, reservoir operators may then
be precluded from operating that reservoir for isheries management without a change in that rule
curve, for some federal facilities this would require a reauthorization by Congress. Also, regulated
rivers are impacted not only by instream modiications but also by modiications and developments
in the watershed. In some cases, for example, local ordinances may preclude the use of some envi-
ronmentally friendly management practices in watersheds, in favor of more traditional methods of
handling stormwater runoff. In some cases, engineers would also need to be trained or retrained in
methods and techniques to better consider environmental values in river design and management.
One recently emerging ield of study that addresses “this generation's problem” with respect
to the watershed is low-impact development (LID). In traditional development practices, the frac-
tion of impervious area in the watershed is increased, with consequent changes in the magnitude
and timing of runoff events. Traditionally, runoff is collected and conveyed through a series of
impervious surfaces in storm drains and detention/retention ponds until the stormwater is treated, if
necessary, and is inally discharged into the receiving stream. The goal of LID is to mimic a site's
predevelopment hydrology to the extent possible by minimizing the impervious area and maximiz-
ing iniltration, using a series of best management practices (BMPs). The BMPs could be green
roofs, iniltration trenches, porous pavements, or other practices designed to iniltrate, ilter, store,
evaporate, and detain runoff close to its source. LID can be a critical component of river manage-
ment and/or rehabilitation.
A second emerging ield of study that addresses “this generation's problem” is ecohydraulics .
Ecohydraulics is becoming increasingly common in government programs and as a ield of study in
academic institutions. As an example of the objectives of ecohydraulics, the following is a list of the
aims of the Eco Hydraulics Committee, Environmental and Water Resources Institute, American
Society of Civil Engineers:

1. To promote the study of the luid mechanics of ecosystems, with the aim of improving our
understanding of such systems, and hence improving our ability to reliably predict and
ameliorate the impact of human intervention in these ecosystems.

2. To encourage the transfer and application of understanding of fundamental transport pro-
cesses and the consequent advancement of engineering practice and technology in the
solution of problems with environmental consequences.

FIGURE 3.33 River. (From the American Society of Civil Engineers.)