Study Classification

Hydrologic engineers in USACE are called upon to provide information for decision making for:

  • Planning and designing flood risk management measures. Hydrologic and hydraulic analyses support comparison of structural and nonstructural alternatives, including their performance under without-project and with-project conditions.
  • Operating and evaluating water-control facilities. Runoff and inflow forecasts support reservoir release decisions and evaluation of operations for authorized purposes.
  • Preparing for and responding to floods. Forecast hydrographs and hydraulic estimates of depths, velocities, and inundation timing support warning, preparedness, and emergency response planning.
  • Providing floodplain information. Runoff, stage, and velocity information supports evaluation of floodplain activities and their effects.
  • Restoring and managing aquatic ecosystems. Flow timing, duration, variability, and sediment information support evaluation of environmental conditions and restoration alternatives.

In addition, since passage of the Rivers & Harbors Act of 1899 USACE has been involved in regulating activities in navigable waterways through the granting of permits. Information about flow depths, velocities, and the temporal distribution of water is vital to the decision making for this permitting.

Study Process Overview

Develop a technical study plan before selecting and applying models. ER 1110-2-1464 (USACE, 1994), paragraph 5, addresses objectives, scope, methods, data, work products, responsibilities, schedule, and resources for watershed-runoff studies. Appendix C of EM 1110-2-1619 (USACE, 2025) consolidates the former EP 1110-2-9 material on a hydrologic engineering management plan (HEMP).

A HEMP identifies the hydrologic and hydraulic information needed by the study team, the analyses that will produce it, and the associated time and cost. Appendix C, paragraphs C-1 and C-2, describes its purpose and use and states that current Civil Works planning policy takes precedence over conflicting guidance in the appendix.

For Civil Works planning studies, ER 1105-2-103 (USACE, 2023), paragraph 1-17b, describes the move to single-phase planning that eliminated the reconnaissance phase. Chapter 2 describes the iterative planning framework. The table below summarizes hydrologic engineering contributions across project activities; it is a technical orientation, and the applicable authority and current planning and project-management requirements govern the process for an individual study.

Description of Project Phases

Project activity

Hydrologic engineering contribution

Planning and feasibility

Define the decisions, study objectives, alternatives, and without-project and with-project conditions. Scope hydrologic and hydraulic analyses, data collection, uncertainty evaluation, and review to support iterative comparison of alternatives.

Preconstruction engineering and design (PED)

Refine design hydrology, hydraulic analyses, and supporting data as needed for design documents, plans, and specifications. Record assumptions and changes from feasibility analyses.

Construction

Provide engineering support, evaluate proposed design changes and relevant observations, and document implications for hydrologic and hydraulic performance.

Operations and later reassessment

Use observations and updated analyses to evaluate performance and support operation, maintenance, repair, and project modifications as applicable.

ER 1110-2-1150 (USACE, 1999), particularly paragraphs 13 through 16, describes engineering work during feasibility, design, construction, and operations. Use it with current planning policy rather than its older reconnaissance-phase description. Update the technical study plan as decisions, information needs, and resources change.