ETL 1110-2-367
31 Mar 95
Chapter 2
on detailed hydraulic design studies of the major features
(USACE 1991).
Analysis Concepts and Procedures for
Interior Areas
2-3.
Hydrologic Engineering Studies
Hydrologic engineering studies are conducted within the
2-1.
Overview
framework of the planning and design processes. The without-
project and with-project conditions must be studied and a
Study strategy includes procedures, assumptions, and activities
hydrologic engineering management plan developed.
associated with the study process. Hydrologic engineering
analyses evaluate interior facilities using present planning
a. Without-project conditions. The initial step is to
guidelines. The interior system is analyzed separate from the
develop stage-frequency relationships at key locations for
line-of-protection project analysis. A minimum outlet facility is
existing without-project conditions. The process is repeated for
required to remove water through the levee or floodwall. This
at least one future time period if conditions affecting hydrology
"minimum" facility, discussed in later chapters, becomes the
and hydraulics change. The process is critical to establish the
starting point from which additional outlet facilities are
formulated. Economic and other analyses are performed for
damage reduction measures and actions to study. For studies
several time- and development-related conditions. These are
with an existing line-of-protection in place, this hydrologic
existing conditions and future conditions for with- and without-
analysis is for the existing system and facilities. Where a new
project features in place (EM 1110-2-1413 and ER 1105-2-
line-of-protection is to be established, a minimum facility must
100).
be evaluated as part of the line-of-protection feature. The
hydrologic analysis of the interior area then includes the
2-2.
Planning Study Phases
minimum outlet as the without-project condition.
There are two phases of the planning study process (ER 1105-2-
b. With-project conditions. After the without-project
100): reconnaissance and feasibility. The preconstruction
conditions are evaluated, a number of flood damage reduction
engineering and design phase follows the planning phases.
plans are arrayed and evaluated. Common interior measures
include gravity outlets, pumping stations, and detention storage
areas. Other measures should also be evaluated, including at
fully funded by the federal government and is normally
least one nonstructural plan (Section 73 of Public Law 93-251),
completed in 12 months. The objectives are to identify the flood
and a flood warning-preparedness program plan that is complete
problem, determine if there is at least one feasible solution that
or a component of a comprehensive plan (ER 1105-2-100).
has a federal interest, identify a local cost-sharing sponsor, and
(assuming a possible project) prepare an initial project
c.
Hydrologic engineering management plan (HEMP).
management plan (IPMP) for the feasibility phase.
The HEMP is a technical outline of the hydrologic/hydraulic
studies necessary to successfully formulate a solution to a
b. Feasibility phase. This second phase takes up to
particular water resource problem. It should be detailed enough
4 years to complete and is cost-shared equally between the
to define the study strategy. It is used to establish resource
federal government and the local sponsor. The objectives of the
allocations and time and cost estimates. Study resources include
feasibility phase are to perform detailed investigations and
personnel, schedules, and funding. Besides being a technical
evaluations of a range of alternatives, and recommend a plan to
guide, a HEMP is valuable in explaining and justifying to the
reduce the flood damage potential.
local sponsor the activities needed for the study and any in-kind
service agreements. The HEMP is also used to define the
c.
Preconstruction engineering and design (PED) phase.
hydrologic engineering requirements for the IPMP. Appendix C
The PED phase continues the design efforts of the recommended
provides an example of a HEMP for an interior area.
plan and encompasses the more detailed construction planning
and engineering necessary for building the project. Major items
2-4.
Study Setting
are a reevaluation report, design documents, and plans and
specifications. For interior area analysis, the key elements of the
Corps studies are normally in urban settings or partially
recommended plan will be reevaluated considering any
developed areas. For some studies, an analysis of agricultural
additional information. If there are no changes, the reevaluation
areas is required. The type and size of the flood damage
report may be brief. Design documents, usually called design
reduction measures studied and implemented are influenced by
memoranda (DM), are required for key features such as
the setting.
pumping stations and major gravity outlet works. Hydrologic
engineering requirements are normally minimal, with emphasis
2-1
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