EP 1110-2-9
31 Jul 94
stream, as well as up tributaries. Proposed projects may
and EM 1110-2-3600 contain additional information in
change the flood hydrology and sediment regime through-
this area.
out the watershed, not just near the proposed project.
Changes in water control management practices at Corps
c. Water supply investigations. The HEMP should
reservoirs can also affect interests remote from the reser-
describe or reference the major study components: exist-
voir site. The hydrologic analysis must include the evalu-
ing project purposes and storage allocations of each,
ation of all positive and negative effects of a potential
upstream and downstream demands, supply analysis,
project or water control management change throughout
hydraulic data (uniform database), drought frequency
the stream system or study area.
analysis (volumes and durations), distribution system
(pumping, conveyance, and storage), etc., for the existing
f. Likely alternatives. The screening process used
and proposed reallocation of reservoir storage. Analysis
in the reconnaissance phase should result in a reduced
may be for one or more severe droughts, although the full
number of alternatives to evaluate in detail for determina-
period of record can be used, similar to water control
tion of the national economic development (NED) plan
management methods. ER 1110-2-241 and ER 1110-2-
during the feasibility phase. The HEMP will include the
1941 contain additional information.
most practical alternative(s) or combinations of alterna-
3-6. Primary Hydrologic Engineering Investiga-
tives to estimate the cost of the hydrologic engineering
tion Products
work effort. The major with-project scenarios must be
developed by the study team for both preliminary and
final scoping of the technical activities. The no-action
The hydrologic engineering results needed by the study
case must also be determined for comparison to the with-
team may include the following information, as discussed
project alternatives. Similarly, agreement should be
by general study type:
reached among study team members, during the HEMP
preparation, concerning the number of iterations (or sizes)
a. Flood damage reduction. The main product will
to be evaluated for each alternative. Three or four sizes
be the damage reduction effects of the selected alternative
for each of two or three alternatives should be adequate
on the floods in the watershed. Supplemental investiga-
for most studies.
tion products could include: discharge-frequency relation-
ships, flood elevations, and areas inundated with and
3-5. Major Hydrologic Engineering Activities
without a specified structural alternative (reservoir, chan-
Required
nel, levee, diversion, pumping plant), stage-duration
relationships, sizes of various alternatives for costing
The Corps typically assesses with- and without-alternative
purposes, sedimentation analyses, residual flooding, flood
conditions for the main study objective(s).
forecasting and warning system, etc. Nonstructural alter-
natives may require only the without-project condition,
a. Flood damage reduction. The HEMP should
since these alternatives affect the stage-damage relation-
describe or reference the major study components: water-
ship only and result in little, if any, change in hydrologic
shed hydrology, river hydraulics, frequency analysis,
or hydraulic relationships.
sedimentation analysis, storage operation, hydraulic
design, etc., for both the with and without alternative
b. Water control management. The main product
condition. Analysis will often involve discrete events,
will be a new or revised set of procedures for project
either actual or, more typically, hypothetical, and will
operation and hydrologic forecasting, contained in a water
include development of uncertainty relationships for risk-
control manual. A range of flows should be addressed,
based analysis. ER 1105-2-100 contains additional infor-
from the inflow design flood to the record drought.
mation in this area.
Effects on the watershed sediment regime could be a
required product. Supplemental investigation products
b. Water control management. The HEMP should
could include: operation procedures, stage-duration and
describe or reference the major study components: flood
frequency, discharge-frequency, emergency operation
control capabilities, storage allocated for various project
procedures, gage data network, computer equipment
purposes, drought augmentation, operational analyses, data
needed, conservation and/or hydropower procedures, flood
systems, forecasting, etc., for the existing and proposed
warning and preparedness procedures, and other required
method of regulation. Analyses usually involve discrete
information.
events and continuous record techniques. ER 1110-2-240
3-4
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