EP 1165-2-1
30 Jul 99
a. Major Outlets. Legislative recognition that the provision
of major drainage outlets is an essential part of and complement to
flood damage reduction improvements, is interpreted to permit major
drainage improvements of natural waterways and their tributaries, and
of existing artificial waterways. Major outlets are designated as
those for the drainage from an organized or contemplated drainage
district, groups of drainage districts, or local governmental unit
such as county, town, or city. Normally, the Federal project for an
outlet drainage channel will consist of works in a natural stream or
existing artificial waterway. However, new artificial drainage
channels may be constructed under the Federal program wherever that
procedure would be technically more effective, environmentally sound,
and would be more economical than improvement of existing drainage
courses. (The costs of major drainage outlets are included with
costs for other project flood control elements and cost shared
accordingly.)
b. Agricultural. In agricultural areas, collection of
drainage water is considered a local responsibility. This includes
such work as ditching, diking, and grading on farms and within local
drainage districts or governmental units. Federal outlets works may
"tie" into such local works.
c. Urban. Flood damage reduction works in urban areas are the
adjustments in land use and the facilities designed to reduce flood
damages in urban areas from overflow or backwater due to major storms
and snowmelt. They include structural and other engineering
modifications to natural streams or to previously modified natural
waterways. In urban or urbanizing areas, provision of a basic
drainage system to collect and convey the local runoff to a stream is
a non-Federal responsibility. Water damage problems may be addressed
under the flood control authorities downstream from the point where
the flood discharge is greater than 800 cubic feet per second for the
10 percent flood (one chance in ten of being exceeded in any given
year) under conditions expected to prevail during the period of
analysis. Drainage areas of less than 1.5 square miles shall be
assumed to lack adequate discharge to meet the above criterion.
Exceptions may be granted in areas of hydrologic disparity producing
limited discharges for the 10 percent flood but in excess of 1800 cfs
for the one percent flood. (ER 1165-2-21)
d. Groundwater. Section 403 of WRDA 1986 defines flood control
to include measures for the prevention of groundwater-induced damages.
Study and analysis of this expanded definition of flood control has
not produced a satisfactory classification system for defining Corps
interest in a groundwater-induced damage prevention program.
Accordingly, budget and authorization support is not available at this
time for a generic program of groundwater-induced damage prevention.
Individual cases involving urban groundwater-induced flooding believed
to have merit within the general context of traditional flood damage
reduction should be referred to CECW-P prior to implying any Corps
interest to potential sponsors.
13-10. Project Cooperation and Cost Sharing. WRDA 1986, superseding
previous legislative provisions, and as amended by WRDA 1996,
established the basic requirements for non-Federal participation in
Federal flood damage reduction projects. Separable costs of
recreation features included in structural and nonstructural flood
damage reduction projects are cost shared 50-percent Federal/50-
percent non-Federal.
13-6
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