HEC-RAS (August 11-13, 2008-24 hours of instruction)

HEC-RAS is a computer program developed at the Hydrologic Engineering Center (HEC). The software allows the user to perform one-dimensional, gradually varied, steady flow analysis. The steady flow component is capable of modeling subcritical, supercritical, and mixed flow regime water surface profiles. The effects of various obstructions-such as bridges, culverts, weirs, and structures in the floodplain-may be considered in the computations. The program can be used for application in floodplain management and flood insurance studies to evaluate floodway encroachments. Special features include multiple plan analyses, multiple profile computations, and multiple bridge and/or culvert-opening analysis.

Topics in the HEC-RAS course include:

• computations of water surface profiles
• bridge and culvert hydraulics
• floodplain determination
• Federal Highway Administration (FHWA) bridge scour computations

The latest version of the HEC-RAS program computes water surface profiles using the standard step method, but the program has also built in the conservation of linear momentum relationship that allows for mixed flow computations where a hydraulic jump may form. The bridge routine incorporates low flow computations using an energy balance, momentum balance, Yarnell's equation, and the contracted opening method used in the WSPRO program. The high flow options include an energy balance and a pressure weir flow computation. A number of different culvert shapes are handled by the program, and the procedures follow the FHWA guidelines for culvert hydraulics.

HEC-RAS has the ability to model multiple openings at any individual river crossing. Types of openings can consist of bridges, culvert groups, and conveyance areas (open channel flow computations). The evaluation of the impact of floodplain encroachments on water surface profiles can be of substantial interest to planners, land developers, and engineers. HEC-RAS contains five optional methods for specifying floodplain encroachments. The FHWA bridge scour equations are also included in the program for those who need to predict scour at bridge piers and abutments.

HEC-RAS represents the next generation of hydraulic software for a Microsoft Windows environment. The program replaces HEC-2. Most federal, state, and local government regulatory agencies have already adopted the program.

HEC-GeoRAS (August 14-15, 2008-12 hours of instruction)

HEC-GeoRAS is a set of procedures, tools, and utilities for processing geospatial data in ArcGIS, using a graphical user interface (GUI). The interface allows the preparation of geometric data for import into HEC-RAS and processes simulation results exported from HEC-RAS. To create the import file, the user must have an existing digital terrain model (DTM) of the river system in the ArcInfo TIN format. The user creates a series of line themes pertinent to developing geometric data for HEC-RAS. The themes created are the stream centerline, flow path centerlines (optional), main-channel banks (optional), and cross-section cut lines, referred to as the "RAS Themes."

Additional RAS Themes may be created/used to extract additional geometric data for import into HEC-RAS. These themes include land use, levee alignment, ineffective flow areas, and storage areas.

Water surface profile data and velocity data exported from HEC-RAS simulations may be processed by HEC-GeoRAS for GIS analysis for floodplain mapping, flood damage computations, ecosystem restoration, and flood warning response and preparedness.

Topics in the HEC-GeoRAS course include:

• data requirements
• advantages and limitations of HEC-GeoRAS

Benefits of attending the HEC-RAS and/or HEC-GeoRAS course(s) include:

• one-on-one instruction and hands-on computer time
• user-friendly computer software
• a personal copy of the software and course materials
• information about what most federal, state, and local government regulatory agencies are adopting