[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: 33CFR222.2]

[Page 209-211]
 
                TITLE 33--NAVIGATION AND NAVIGABLE WATERS
 
         CHAPTER II--CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY
 
PART 222--ENGINEERING AND DESIGN--Table of Contents
 
Sec. 222.2  Acquisition of lands downstream from spillways for hydrologic safety purposes.

    (a) Purpose. This regulation provides guidance on the acquisition of 
lands downstream from spillways for the purpose of protecting the public 
from hazards imposed by spillway discharges. Guidance contained herein 
is in addition to ER 405-2-150.
    (b) Applicability. This regulation is applicable to all OCE elements 
and all field operating agencies having civil works responsibilities.
    (c) Reference. ER 405-2-150.
    (d) Discussion. A policy of public safety awareness will be adhered 
to in all phases of design and operation of dam and lake projects to 
assure adequate security for the general public in areas

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downstream from spillways. A real estate interest will be required in 
those areas downstream of a spillway where spillway discharge could 
create or significantly increase a hazardous condition. The real estate 
interest will extend downstream to where the spillway discharge would 
not significantly increase hazards. A real estate interest is not 
required in areas where flood conditions would clearly be nonhazardous.
    (e) Hydrologic criteria. The construction and operation of a dam and 
spillway may create or aggravate a potential hazard in the spillway 
discharge area. Therefore, an appropriate solution should be developed 
in a systematic manner. All pertinent facts need to be considered to 
assure that the risk to non-Federal interests does not exceed conditions 
that would prevail without the project. General hydrologic engineering 
considerations are as follows:
    (1) Probability of spillway use. Pool elevation versus probability 
of filling relationships can change materially after initial 
construction. Spillway use may be more frequent than anticipated. The 
infrequent use of a spillway is not a basis for the lack of adequate 
downstream real estate interest.
    (2) Changes in project functions. Water resource needs within river 
basins change and pool levels may be adjusted to provide more 
conservation storage, particularly when high-level limited-service 
spillways are provided. Such changes normally increase spillway use and 
are to be considered.
    (3) Volume and velocity of spillway flow. The amount of flow and 
destructive force of the flow from a spillway during floods up to the 
spillway design flood can vary from insignificant to extremely hazardous 
magnitudes. The severity and area of hazard associated with spillway 
discharge will vary depending on specific project site conditions. 
Therefore, the hazard is to be analyzed on a project-by-project basis.
    (4) Development within floodway. If development within the floodway 
downstream from a spillway is not present at the time of project 
construction, the existence of the reservoir may encourage development. 
Adverse terrain conditions do not preclude development. Sparse present 
development is not a basis for lack of real estate acquisition.
    (5) Debris movement within floodway. The availability of erodible 
material in a spillway flow area intensifies the hazards of spillway 
flow. In fact, debris may be transported to downstream areas that 
otherwise would not be adversely affected. Extreme erosion may result 
from high velocities and turbulence. Both debris and erosion must be 
evaluated and considered.
    (6) Flood warning and response potential. Small projects generally 
have short time periods available to warn downstream inhabitants and may 
be unattended prior to spillway use. The ability to convince individuals 
to leave most of their worldly possessions to the ravages of spillway 
flow may be severely limited. In some cases flood warning systems may be 
necessary; however, this subject is beyond the scope of this regulation. 
Warning systems are not an adequate substitute for a real estate 
interest in lands downstream of spillways.
    (7) Location of spillway. Spillways should be located to minimize 
the hazards associated with their discharge and the total project cost 
(cost of spillway structure and downstream lands). Spillways, outlet 
works, stilling basins, and outlet channels should be designed to 
minimize hazards to downstream interest insofar as is engineeringly and 
economically reasonable.
    (f) Real estate. The real estate interest required downstream of 
spillways will be adequate to assure carrying out project purposes and 
to protect non-Federal interest from hazards created by spillway flows. 
The interest may be either fee or permanent easement. A permanent 
easement must exclude all overnight and/or permanent habitation, 
structures subject to damage by spillway flows and activities that would 
increase the potential hazards. No real estate interest is required for:
    (1) Areas where the imposed or aggravated flood condition is non-
hazardous. Affected interest should be informed of the nature of the 
imposed non-hazardous flood condition.
    (2) Areas where the construction and operation of a dam and spillway 
do not

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increase or create a hazardous condition.
    (g) Alternative land uses. In some cases land downstream from 
spillways can be effectively used for purposes other than hydrologic 
safety. Therefore, the entire cost of these lands may not be an 
additional project cost. For example, the lands downstream of a spillway 
may be used for wildlife management essential to project purposes in 
lieu of other lands suitable for similar purposes at another location.
    (h) Procedural guidance. Procedures regarding the application of the 
principles outlined in the above paragraphs are as follows:
    (1) For various flood magnitudes up to the probable maximum flood 
determine the ``with'' and ``without project'' flood conditions 
downstream of a dam spillway for the following:
    (i) Flooded area.
    (ii) Flood depth.
    (iii) Flood duration.
    (iv) Velocities.
    (v) Debris and erosion.
    (2) Determine the combinations of flood magnitudes and the above 
flood conditions that could be the most hazardous and/or result in the 
greatest increase in hazard from ``without'' to ``with project'' flood 
conditions. Designate these combinations of flood magnitude and flood 
conditions as the critical conditions.
    (3) For the critical conditions selected above outline the areas 
where the project could increase and/or create (impose) one or more of 
the critical conditions. Areas where spillway flows do not create or 
increase flood conditions are excluded from further analysis.
    (4) Determine where the imposed critical conditions as outlined 
above would be hazardous and non-hazardous. Non-hazardous areas are 
defined as those areas where:
    (i) Flood depths are maximum of 2 feet in urban and rural areas.
    (ii) Flood depths are essentially non-damaging to urban property.
    (iii) Flood durations are a maximum of 3 hours in urban areas and 24 
hours in agricultural areas.
    (iv) Velocities do not exceed 4 feet per second.
    (v) Debris and erosion potentials are minimal.
    (vi) Imposed flood conditions would be infrequent. That is, the 
exceedence frequency should be less than 1 percent. Hazardous areas are 
those where any of the above criteria are exceeded.
    (5) Based upon the information developed above and the principles 
outlined in paragraphs (c) through (f) of this section, decide on the 
extent of area and estate required for hydrologic safety purposes.
    (i) Reporting. Lands to be acquired downstream from spillways and 
intended purposes will be identified and the cost included in 
feasibility reports and real estate design memoranda. Additional 
specific information in support of land acquisition should be provided 
in Phase I or Phase II general design memoranda (GDM) and dam 
modernization reports. This information should include topographic maps, 
area flooded maps, velocities, erosion and debris areas ``with'' and 
``without'' the project. Real estate boundaries and discussions of items 
in paragraph (h)(4) are also essential in the GDM's and dam 
modernization reports.

[43 FR 35481, Aug. 10, 1978. Redesignated at 60 FR 19851, Apr. 21, 1995]