ETL 1110-2-367
31 Mar 95
Chapter 6
Existing system layout: schematics, aerials, tables,
plates, maps.
Study Documentation
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Existing facilities on aerials
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Important environmental aspects
6-1.
General Requirements
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Damage locations
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Cultural features
This chapter emphasizes the role of HEC-IFH in study
documentation as related to final technical studies reports.
Description of physical features of existing (without)
Comprehensive, but concise, documentation of the hydrologic
conditions.
engineering analysis is a key aspect of any study. It should be
performed continuously throughout the study period. Required
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Watershed/subbasin boundaries on map
hydrologic engineering information ranges from extensive (for
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Dimensions of any existing gravity outlets, channels,
feasibility reports) to relatively little (for most Design
storm sewers, etc. (HEC-IFH)
Memoranda (DM) where more emphasis is placed on hydraulic
Area capacity data of detention areas (HEC-IFH)
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design). Reporting requirements for different types of studies
are described in applicable Engineer Regulations (ER's). In
Description of basic hydrologic approach/ assumptions.
addition, hydrologic and hydraulic Engineer Technical Letters
(ETL's) summarize the array of hydrologic engineering data that
Historic/hypothetical storms (HEC-IFH)
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must be presented for planning reports and suggest display
Loss rates (HEC-IFH)
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formats. The goal of study documentation should be to describe
Runoff transforms (HEC-IFH)
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(in a basic and orderly sequence) the nature of the flood
Routing (HEC-IFH)
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problem, the status and configuration of the existing system, the
Base flow (HEC-IFH)
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proposed system and alternatives, the performance
characteristics of the proposed system, and operation plans.
Presentation of hydrologic flow characteristics.
6-2.
Content Related to Planning
Peak discharge (HEC-IFH)
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Considerations
Duration (HEC-IFH)
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Frequency (HEC-IFH)
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Hydrologic reporting requirements should include a description
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Velocity
of the without-project conditions, alternate flood loss reduction
plans analyzed, analytical procedures and assumptions used, and
Impact of future without-project conditions.
system implementation and operation factors influencing the
hydrologic aspects of the study. Basic hydrologic reporting
-
Description of runoff and operation changes similar to
requirements are specified in ER 1105-2-100 and EM 1110-2-
existing conditions
1413.
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Description of adopted procedures for parameter
6-3.
Content Related to Design Considerations
estimation
Hydrologic analysis of alternatives.
Hydrologic engineering material presented in the design
documents describes in detail the hydrologic system, and any
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Location, dimensions, and operation criteria of alternate
refinements of sizes, performance standards, and operation
plans
criteria from the feasibility study. The hydrologic engineering
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Display of final array of plans on aerials - compare with
requirements for the DM are specified in ER 1110-2-1150.
existing
6-4.
Reporting Capabilities of HEC-IFH
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Impacts of measures and plans on peak discharges,
durations, velocities, etc. (HEC-IFH)
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Display of residual effects of large SPF/PMF in urban
HEC-IFH has extensive reporting and plotting capabilities that
areas, and 100-year in rural (HEC-IFH)
document the results of an interior analysis. The data stored in
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Hydrologic description of alternate plans shall include
each data module, as well as hydrologic analysis summaries and
description of required local agreements/ maintenance
plan comparison results, can be printed or plotted to provide
requirements
report documentation. The following outline, which follows the
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Description of consequences if agreements are not met
requirements of EM 1110-2-1413, also indicates technical study
(HEC-IFH)
areas in which tables and plots from the HEC-IFH program may
be used for documentation.
Design information.
6-1
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