[Code of Federal Regulations]

[Title 33, Volume 3]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 33CFR238.7]



[Page 327-329]

 

                TITLE 33--NAVIGATION AND NAVIGABLE WATERS

 

 CHAPTER II--CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY, DEPARTMENT OF 

                                 DEFENSE

 

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 328]]



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 329]]



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.