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Hydrology (HEC-HMS & HEC-1)

Some agencies may still require HEC-1 models to be used for a study or if you are importing a HEC-1 model into HEC-HMS we recommend that you run the model using HydroPro first to see if there are any error messages. The following descriptions of both programs are provided.

HEC-HMS, Hydrologic Modeling System (Windows)

HEC-HMS is the Windows-based computer program that replaces HEC-1. HEC-HMS designed to simulate the precipitation-runoff processes of dendritic watershed systems. It is designed to be applicable in a wide range of geographic areas for solving the widest possible range of problems. This includes large river basin water supply and flood hydrology, and small urban or natural watershed runoff. Hydrographs produced by the program are used directly or in conjunction with other software for studies of water availability, urban drainage, flow forecasting, future urbanization impact, reservoir spillway design, flood damage reduction, floodplain regulation, and systems operation.

The program is a generalized modeling system capable of representing many different watersheds. A model of the watershed is constructed by separating the hydrologic cycle into manageable pieces and constructing boundaries around the watershed of interest. Any mass or energy flux in the cycle can then be represented with a mathematical model. In most cases, several model choices are available for representing each flux. Each mathematical model included in the program is suitable in different environments and under different conditions. Making the correct choice requires knowledge of the watershed, the goals of the hydrologic study, and engineering judgment.

The program features a completely integrated work environment including a database, data entry utilities, computation engine, and results reporting tools. A graphical user interface allows the seamless movement between the different parts of the program. Program functionality and appearance are the same across all supported platforms.

HEC-1, Flood Hydrograph Package (DOS)

All ordinary flood hydrograph computations associated with a single recorded or hypothetical storm can be accomplished with this package. Capabilities include rainfall-snowfall-snowmelt determinations; computations of basin-average precipitation from gages or hypothetical storms; unit hydrographs via direct ordinates or Clark, Snyder or SCS methods, or by kinematic wave transforms; hydrograph routing by level-pool reservoir, average-lag, modified Puls, Muskingum, Muskingum-Cunge, and kinematic wave methods; and complete stream system hydrograph combining and routing. Best-fit unit hydrograph, loss-rate, snowmelt, base freezing temperatures and routing coefficients can flow over and through breached dams. Expected annual flood damage can also be computed for any location in a river basin. Interfaces with HEC-DSS routines for storing, retrieving, graphing, and tabulating data.

Hydraulics (HEC-RAS & HEC-2)

Although HEC-RAS has replaced HEC-2, some agencies may still require HEC-2 models to be used for a study. If you are importing a HEC-2 model into HEC-RAS we recommend that you run the model using HydroPro first to see if there are any error messages. The following descriptions of both programs are provided.

HEC-RAS, River Analysis System (Windows)

HEC-RAS is the Windows-based computer program that replaces HEC-2. HEC-RAS was developed by the U.S. Army Corps of Engineers Hydrologic Engineering Center in Davis, CA. HEC-RAS incorporates several aspects of hydraulic modeling, including water surface profile computations, bridge hydraulics, one-dimensional steady flow, and unsteady flow simulation.

The HEC-RAS system contains four one-dimensional river analysis components for: (1) steady flow water surface profile computations; (2) unsteady flow simulation; (3) movable boundary sediment transport computations; and (4) water quality analysis. A key element is that all four components use a common geometric data representation and common geometric and hydraulic computation routines. In addition to the four river analysis components, the system contains several hydraulic design features that can be invoked once the basic water surface profiles are computed.

HEC-2, Water Surface Profiles (DOS)

The HEC-2 program computes water surface profiles for one-dimensional steady, gradually varied flow in rivers of any cross section. Flow may be subcritical or supercritical. Various routines are available for modifying input cross-section data; for example, for locating encroachments or inserting a trapezoidal excavation on cross sections. The water surface profile through structures such as bridges, culverts and weirs can be computed. Variable channel roughness and variable reach length between adjacent cross sections can be accommodated. Input may be in either English or metric units.

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© 2012 - Walter P. Moore & Associates, Inc. - Houston, TX, USA