[Code of Federal Regulations]
[Title 33, Volume 3]
[Revised as of July 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 33CFR238.7]

[Page 318-320]
 
                TITLE 33--NAVIGATION AND NAVIGABLE WATERS
 
         CHAPTER II--CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY
 
PART 238--WATER RESOURCES POLICIES AND AUTHORITIES: FLOOD DAMAGE REDUCTION MEASURES IN URBAN AREAS--Table of Contents
 
Sec. 238.7  Decision criteria for participation.

    (a) Urban flood control. (1) Urban water damage problems associated 
with a natural stream or modified natural waterway may be addressed 
under the flood control authorities downstream from the point where the 
flood discharge of such a stream or waterway within an urban area is 
greater than 800 cubic feet per second for the 10-percent flood (one 
chance in ten of being equalled or exceeded in any given year) under 
conditions expected to prevail during the period of analysis. Those 
drainage areas which lie entirely within the urban area (as established 
on the basis of future projections, in accordance with Sec. 238.5 of 
this part), and which are less than 1.5 square miles in

[[Page 319]]

area, shall be assumed to lack adequate discharge to meet the above 
hydrologic criteria. Those urban streams and waterways which receive 
runoff from land outside the urban area shall not be evaluated using 
this 1.5 square mile drainage area criterion.
    (2) A number of conditions within a drainage area may limit 
discharges for the 10-percent flood, without proportionately reducing 
discharges for larger floods, such as the one-percent flood. Examples 
include the presence of extremely pervious soils, natural storage 
(wetlands) or detention basins or diversions with limited capacity. 
Other conditions could result in a hydrological disparity between the 
10- and one-percent flood events.
    (3) Division Engineers, except for NED and POD, are authorized to 
grant exceptions to the 800 cfs, 10-percent flood discharge criterion 
specified in this Sec. 238.7(a)(1) whenever both of the following 
criteria are met:
    (i) The discharge for the one-percent flood exceeds 1800 cfs; and
    (ii) The reason that the 10-percent flood discharge is less than 800 
cfs is attributable to a hydrologic disparity similar to those described 
in Sec. 238.7(a)(2).

Requests for exceptions to the hydrologic criterion contained in 
Sec. 238.7(a)(1) from NED and POD should be submitted to HQDA (DAEN-CWP) 
WASH DC 20314.
    (4) Flood damage reduction works must conform to the definition in 
Sec. 238.4(b) and must be justified based on Corps of Engineers 
evaluation procedures in use at the time the evaluation is made. Flood 
reduction measures, such as dams or diversions, may be located upstream 
of the particular point where the hydrologic criteria (and area 
criterion, if appropriate) are met, if economically justified by 
benefits derived within the stream reach which does qualify for flood 
control improvement. Similarly, the need to terminate flood control 
improvements in a safe and economical manner may justify the extension 
of some portions of the improvements, such as levee tiebacks, into areas 
upstream of the precise point where Federal flood control authorities 
become applicable.
    (b) Storm sewer system. Water damage problems in urban areas not 
consistent with the above criteria for flood control will be considered 
to be a part of local storm drainage to be addressed as part of the 
consideration of an adequate storm sewer system. The purpose of this 
system is to collect and convey to a natural stream or modified natural 
waterway the runoff from rainfall or snowmelt in the urbanized area.
    (c) Man-made conveyance structures. (1) Man-made conveyance 
structures will be assumed to be a part of storm sewer systems except 
when: (i) A natural stream has been or is to be conveyed in the man-made 
structure; or (ii) The man-made structure is a cost-effective 
alternative to improvement of a natural stream for flood damage 
reduction purposes or is an environmentally preferable and economically 
justified alternative. Water damage associated with inadequate carrying 
capacity of man-made structures should be designated as a flood problem 
or a local drainage problem in a manner consistent with the structure's 
classification as flood damage reduction works or a part of a storm 
sewer system.
    (2) Man-made structures that convey sanitary sewage or storm runoff, 
or a combination of sanitary and storm sewage, to a treatment facility 
will not be classified as flood damage reduction works. Flows discharged 
into a natural or previously modified natural waterway for the purpose 
of conveying the water away from the urbanized area will be assumed to 
be a part of the flow thereof regardless of quality characteristics.
    (d) Joint projects. Certain conditions may exist whereby the Corps 
of Engineers and the Department of Housing and Urban Development (HUD), 
or another Federal agency, could jointly undertake a project that would 
be impractical if one agency were to undertake it alone. The Corps may, 
for example, under provisions of Section 219 of the Flood Control Act of 
1965, design or construct a project that is part of a larger HUD plan 
for an urban area (see ER 1140-2-302). Such efforts should be undertaken 
only when requirements cannot be handled better by one agency

[[Page 320]]

acting alone. If a joint effort is preferable, then the Corps may 
participate as required.
    (e) Disagreements. If a disagreement arises between the Corps and 
another Federal agency that cannot be resolved at the field level, the 
matter will be forwarded to HQDA (DAEN-CWR) WASH DC 20314 for guidance.