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This release of HEC-RAS is a major upgrade of the previous version. Several new features have been added for unsteady flow routing as well as steady flow water surface profile calculations. Here is an overview of the new features and enhancements available with HEC-RAS 3.1.3.

• Unsteady Flow Routing Features
• New Geometric Data Features
• New Hydraulic Design Functions
• Graphical and Tabular Output
• Other New Features

The following is a list of features for unsteady flow routing that can be found in HEC-RAS 3.1.3.

• Levee Failure Analysis
  HEC-RAS can now perform a levee failure analysis. The user enters information about the size and dimensions of the failure, as well as how long it will take to form. The software will then perform unsteady flow routing of the flood wave through the failure and on down stream.
• Mixed Flow Regime For Unsteady Flow
  HEC-RAS can now perform mixed flow regime (subcritical to supercritical, as well as hydraulic jumps) calculations during an unsteady flow run.
• Pump Stations
  HEC-RAS now has the capability to model pump stations. The user can attach a pump station to a storage area or a river reach. Each pump station can have up to 10 non-identical pump groups, for which a different pump efficiency curve (head versus flow) can be entered. Each pump group can have up to ten identical pumps (same pump efficiency curve). However, every pump can have a different on and off trigger elevation.
• Navigation Dams
  This feature will optimize gate settings for a navigation dam in order to maintain an upstream water surface within a specified range.
• Culvert Flap Gates
  This feature allows the user to put a flap gate on a culvert that is defined as part of a lateral structure. The flap gate can be set to allow water to only flow in one direction through the culvert.
• Floodway Encroachments
  Floodway encroachments can now be analyzed during an unsteady flow simulation.
• New Flow Data and Boundary Conditions Features
  Several new features have been added to the Unstead Flow Data editor. The following is a list of those features:
• Internal River Station Stages:
  allows the user to set a water surface at any river station for the initial conditions.
• Minimum Flow and Flow Ratio Table:
  This option allows the user to specify a minimum flow for any of the flow hydrograph boundary conditions being used in the simulation. Additionally, there is an option to enter a ratio that will be multiplied by every ordinate in a flow hydrograph boundary condition.
• Observed (Measured) Data:
  In the previous version of HEC-RAS the user could specify a DSS pathname that contained observed flow or stage time series data. When this is done, that observed data can then be plotted with computed values on hydrograph plotter, profile plots, and cross section plots. Two new options have been added, High Water Marks and measure Rating Curves (mean curve and measured points can be entered). When high water marks are entered, they will show up on the profile plots as well as the cross section plots. When entereing measured rating curves, the user-entered mean curve and measured points will show up on the rating curve plots, along with the computed values.
• Initial Conditions Flow Optimization
  This option allows the user to direct the program to try to optimize the flow at junctions and lateral structures for the calculation of the initial condtions. Initial conditions are computed with a standard step backwater, and it is up to the user to put in initial estimates of the flow. Sometimes these estimates do not always result in consistent water surfaces for initial conditions...which in turn can cause the unsteady flow calculations to go unstable right at the beginning of the simulation. By optimizing flow splits and flow leaving the main river, these instabilities may be minimized. This option is available from the Options menu of the Unsteady Flow Analysis window.
• Log File Output
  The Log File Output for Unsteady flow calculations has been dramatically improved. The log file is used to assist users in debugging computational problems. User’s now have much more control over what and how much information gets written to this file. Additionally, the format of the information has been made easier to read and understand.

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• Improved Background Map Viewing for River System Schematic
  We have changed the background mapping and imaging capability within thegeometric editior to allow for a wider range of image types. We are now using a commercial package from ESRI, called Map Objects Light (ESRI, 2002). This package is a library of routines that can be used for map and image display. There is no licensing fee or requirement to have any other ESRI product in order for this to work.
• New Terminology for Inline and Lateral Structures, as well as Storage Area Connections
  Previously in version 3.0, we used the terms “Inline Weir/Spillway”, “Lateral Weir/Spillway”, and “Hydraulic Connections”. These terms have been changed to more generic names in order to account for the fact that we now allow for a wider range of hydraulic features to be combined at each of these structure types. The new names, and their use are described below:
• Inline Structure:
  Can be used to model a hydraulic structure that crosses the main stream. This structure can have gated spillways, as well as a free flowing overflow weirs/spillways.
• Lateral Structure:
  Can be used to model a hydraulic structure that is lateral (parallel) to the main river. This type of structure can remove flow from the river, or bring flow into the river. A lateral structure can be connected to a Storage Area or to another river reach. Lateral structures can contain gated spillways, culverts, free flowing overflow weirs/spillways, and user-defined diversion rating curves. Additionally, an option exists to perform a simple linear routing between the river and to whatever the lateral structure is connected.
• Storage Area Connections:
  Storage area connections allow the user to model the transition of flow from one storage area to another. This option allows the user to define a hydraulic structure using a free flowing weir, weir and gated spillways, weir and culverts, or a simple linear routing option.
• Flow and Seasonal Roughness Factors Stored in Geometry
  Previously, when a user defined a flow versus roughness or seasonal roughness change, the information was stored as part of the Plan file. This capability allowed a modeler to make changes to the roughness without re-running the geometric preprocessor (this is a common need in real-time forecasting). However, it is recognized that these changes may also be appropriate as permanent values that should always be applied to the geometry data. Therefore, we have added the same features directly into the gemometric data editor. These two features can be found under the Tools menu bar of the Geometric Data Editor. They are generally used for unsteady flow modeling, but the flow versus roughness can also be used for steady flow modeling.
• Improved Display of Information on The River System Schematic
  We have added the ability to highlight in red the current active node (cross sesction, bridge, culvert, hydraulic structure, etc.). Additionally, a red circle is drawn around it in order to make it easy to find on the schematic. The active node is whichever node was the last one to be viewed in a data editor or output window.
• New Data Editing Tables For Geometric Editor
  The following data editor tables have been added to the geometric editor (under the Tables menu bar), to allow easier editing of multiple locations and global information: Levee Elevations; Node Descriptions; Pricture File Associations; Weir and Gate Coefficients; and HTAB Internal Boundaries (Geometric Pre-processor).
• New Data Manipulation Tools For Geometric Editor
  The following is a list of the new geometric editor tools that have been added: View reach connectivity; Datum adjustment; Fix overlapping ineffective areas; GIS coordinates manipulation; Reach order for computations; and Find loops in river system schematic.

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In addition to the existing pier scour function, HEC-RAS can now perform uniform flow computations, stable channel design, and sediment transport capacity computations for existing geometry.

• Uniform Flow Computations
  For a selected cross section, any of the parameters of Manning’s equation can be computed, when the other parameters are input by the user. For examples, if the user wishes to know the discharge, the slope and water surface elevation must be entered along with the existing cross section, and the discharge will be solved. A number of different roughness analysis techniques can be used, including Manning, Strickler, Keulegan, Limerinos, Brownlie, and the SCS Grass Curves. Channel width can also be solved, but in this case, an idealized cross section with up to three trapezoidal templates must be used.
• Stable Channel Design
  This function can be used to determine the channel geometry and characteristics needed to archive channel stability at a given cross section. The user has the choice of using Copeland’s method, Regime method or Tractive Force method. Similar to the Uniform Flow Computations, a number of parameters are entered by the user, and RAS outputs the parameters required for channel stability. For this function, only idealized trapezoidal channels can be used.
• Sediment Transport Capacity
  The sediment transport capacity at any existing cross section can be determined using this feature. Six transport methods are available, which include Ackers-White, Engelund-Hansen, Laursen, Meyer-Peter Muller, Toffaleti, and Yang. Transport Capacity can be analyzed for the main channel or overbanks and by grain size for each water surface profile selected. output is presented in sediment profile plots, sediment rating curve plots, and their respective tables. The plots have the option to display general results such as total sediment transport capacity for the entire cross section, or specific results such as sediment transport capacity for a given grain size in the main channel only.

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• Cross-Section Plots
  New animate, record, and picture buttons have been added to the cross-section plot. The Animate button allows you to animate the change in water surfaces over time for an unsteady flow run; the Record button allows you to record an AVI movie file of the animation; and the Picture button allows you to view or attach a picture to specific cross sections. Also, the “A” and “Z” keys can be used to show similar plots up and down the river system.
• Profile Plot
  New buttons have been added to this plot to make it more convenient to select river reaches and which profiles to plot. Additionally, buttons for animating the plot, recording an AVI movie of the animation, and reloading the data from a new run have been added.
• Rating Curve Plot
  The animate, record AVI, and picture buttons have been added to this plot as described above.
• Hydrograph Plots
  The following new features have been added to the hydrograph plotting capability:
• Hydrograph Statistics
  A window has been added to the upper right hand corner of the plot window to display statistics about the computed flow and stage hydrographs, as well as any observed data at this location. The statistics include the peak stage and time, the peak flow and time, and the volume of the hydrograph. If observed data are attached at this location, additional statistics will appear, including: observed peak stage, time, and lag (difference in computed and observed stage times); observed peak flow, time, and lag; and observed volume, difference between computed and observed volume and percent difference in volume.
• Calibration Aids
  Tabs have been added for a rating curve plot, computed minus observed stage versus flow, and computed minus observed stage versus season. The rating curve plot is different than the general one in that it plots stage versus flow sequenced in the time that they actually occurred. This plot can show any loops in the rating curve that may have been computed or observed. The computed minus observed stage versus flow tab shows how the errors in the computed minus observed stage versus season tab shows the errors that may vary over time. All of these tabs are very useful when calibrating an unsteady flow model.
• Selecting Variables To Plot
  New check boxes have been added directly above the tabs to allow the user to quickly turn variables on or off. This includes stage, flow, observed stage, observed flow, and whether or not to use a reference elevation for scaling the plot (invert of the cross section is used as minimum elevation for stage scale).
• 3-D Graphic
  Users can now display the river stations on this plot.
• Hydraulic Tables Plot (HTAB)
  A new button has been added to this plot in order to more conveniently turn the plot variables on and off.
• Detailed Output Tables
  Some new table types have been added to the detailed output table window, these include: multiple openings, storage areas, storage area connections, and pump stations. Additionally, a Plan selection button has been added to the window in order to view detailed output from other plans without opening the entire plan data.
• Summary Output Tables
  A new summary table type has been added for pump stations. Additionally, we have added the ability for a user to create a table that contains only the specific list of specified locations, the new summary table can be saved for later recall.
• DSS Viewer
  The HEC-DSS viewer has been updated to handle larger DSS files.
• General Graphics Features
  The following items have been added to all of the 2-D graphics:
• With the mouse over the graphic, if you click the left mouse button, the program will find the nearest point and display its river and reach name, river station, and X and Y value.
• All of the data values that make up the graphic can be copied to the clipboard. This can be accomplished from the File menu of each graphic.
• The user can measure distances on the graphic by holding down the control key and then moving the mouse. When the control key is released, the measured distance is displayed.
• Cross-Section Editor
  The graphic of the cross section is more closely tied to the cross section data editor. Data in the plot changes when the Apply Data button is pressed on the editor. The plot also changes to a new cross section when a new cross section is selected from the editor.

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• DSS Viewer has a new utility to copy DSS paths.
• If observed DSS pathnames are added to the unstead data editor, the cross section locations are automatically added to the flow and stage output locations (HY records).
• The stage-flow plotter allows users to set the number of decimal places in the table.
• Edits to line and symbol style now persist until a plot is closed.
• The flow and stage plotter now shows a vertical red line at the time of the current profile viewed in animation.
• Profile Plot now shows River names with the Reach names in the space above the plot.

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