2D Connections - Bridge Skew - The capability to skew bridge information for 2D connections is available from the Options | Skew Bridge Data menu item. The user applies angle which is used to adjust the station-elevation but multiplying it by the cosine of the angle.  A preview of the skewed bridge data will be shown to the user.  The ground line represents the data in the table (that the user can change).  The skewed lines and bridge deck information will then be used to create the table of hydraulic bridge curves (computed prior to the unsteady flow simulation).

Hydraulic Structure Weir Computations - Weir flow computations have been improved for hydraulic structures connected to 2D cells.  Previously, the water surface was computed based on water surface elevation values at the cell face points.  The new method utilizes the face points and the center of each face along the hydraulic structure for computing the water surface profile for the headwater/tailwater.  This new computation method will increase the accuracy with which weir flow is computed and give different answers from previous versions.  In addition, the hydraulic structure is now checking the hydraulic connectivity between adjacent cells to more accurately compute the water surface at the face point.

Simplified 2D Bridge Improvements - Simplified 2D bridge modeling refers to the approach of using 1D bridge hydraulic calculations to estimate changes in water surfaces through bridges as a function of flow and enforcing the 2D flow model to match the 1D bridge curves. The approach is designed for capturing the overall energy losses through a bridge with a 2D model for all ranges of flows without requiring a high-resolution mesh or modeling the hydraulically challenging pressured flows or overtopping flows in the 2D model. The method is not designed for detailed bridge hydraulics within the bridge. Simplified 2D bridges modeling was introduced in HEC-RAS 6.0 and has gone through several revisions in versions. In HEC-RAS 6.5 Beta, the simplified 2D bridge modeling approach has been modified and improved significantly. Importantly, previous versions of HEC-RAS had a limitation on how small cells could be near bridges. HEC-RAS 6.5 removed this limitation and is thus more flexible and user-friendly. The approach for matching the 1D bridge curves is very simple and uses an iterative method for adjusting a spatially uniform simple drag factor at all faces underneath each bridge. Several new time-series plots are available for 2D bridges within 2D areas including the drag factor and total head-loss through the bridge. 

National Levee Database - HEC-RAS has incorporated the ability directly download and utilize NLD data within a RAS Terrain as a Terrain Modification. The NLD organizes data by Levee System and individual levee Segments.  The Levee System is a continuous alignment line with elevations, while the levee Segment provided other information about the sections of the levee.  Each levee Segment is comprised by a particular feature type (Centerlines, Floodwalls, and Closure Structures).  There are additional features in the NLD; however, the information along the Levee System are the pieces of information (levee alignment and elevations) HEC-RAS will use for the Terrain Modification.



Model Comparison Tool - The Model Comparison Tool in HEC-RAS in intended to allow users to evaluate the components of an HEC-RAS project to identify differences in the primary modeling objects.  Differences in the project files, geometry, flow, and results can be visualized through tables and spatial plots.

Encroachments - The Floodway Encroachment Analysis tools have been improved for version 6.5.  This includes several bug fixes including the saving data Terrain Modification Slope and Additional Fill properties, improvement of the Terrain Modification routine, allowing culverts in the floodplain to be blocked, and updating data layers and plots. New tools for evaluating the floodplain through map values have been added by being able to Plot Contour at Cursor and Track Velocity at Cursor.  The Plot Contour at Cursor will interactively contours the selected dataset using the value of map cursor, while the Track Velocity at Cursor plot option will trace a longitudinal and transverse velocity based on the cursor's location.

Capacity Only/Concentration Only Sediment Modeling Modes (2D): The 2D sediment model includes these two "fixed bed" sediment modeling approaches, that add value and information over "competence" type shear stress analyses, but do not require the modeling effort, data, or run time of a full mobile-bed, sediment transport model.  

Updates to the Sediment Rating Curve Calculator: Version 6.5 includes several improvements and updates to the sediment rating curve calculator.

  • The tool computes the piecewise linear regression based on the stationarity analysis (historic=data before the stationarity threshold and contemporary=data after).
  • The annual load computation updates based on piecewise linear and/or stationarity selections in the model (see figure below).
  • The tool can convert flow and load data between US Customary and SI (metric) units.
  • The tool averages same-day data by default.

Length Scale for the Rouse-Diffusion 1D Deposition Method: The Rouse-Diffusion method under predicts floodplain deposition for wide floodplains because concentration is a function of the wetted width of the floodplain.  Version 6.5 includes an optional (but encouraged) user defined length scale that allows users to focus the deposition region to the natural levee zone near the channel.  This will increase deposition over the current method, but still limits deposition to the grain classes and concentration that is available to deposit.  

Global Deposition Threshold (2D):  User can specify a global critical shear for deposition for all grain classes. This parameter is useful for simplified, mobile bed, (Concentration Only) debris flow simulations because it will transport the entire, specified, non-Newtonian load (with its concentration) until the pulse slows to a depositional regime.  This mode allows simplified, variable concentration simulations (e.g. non-Newtonian dam breach) without a full, mobile bed, modeling approach.

Use Equilibrium Load Boundary Condition for Unspecified Grain Classes: It can be advantageous to use measured data for finer grain classes and equilibrium load for coarser grain classes (e.g. unmeasured load, bed load, etc.).  Version 6.5 includes capabilities that allow users to combine data and equilibrium load for different grain classes in the same boundary condition.

Convergence Error Messages for 2D Sediment: When the 2D sediment model did not converge (but the hydraulics did) the runtime editor did not alert the user in previous version.
Therefore, the sediment model often failed without warning or indication which cells were causing trouble.  Users had to go to the  Computational Level Output to evaluate sediment convergence.

Version 6.5 includes runtime convergence alerts, that tell users which cell (and grain class) had the largest convergence errors in any time step.
Like hydraulic stability runtime messages, sediment convergence messages do not mean the model is unusable, but they will provide a starting point for troubleshooting.

Sediment Competence Output: Version 6.5 includes a "Competence" result for sediment. 
The Competence result (below) maps the largest movable grain size for at the time step.
(Assuming a Shields number of 0.03 and no hiding/exposure or other corrections)

Sediment and Debris Videos and Tutorials: HEC has posted two new sediment and debris tutorials to accompany the 6.5 release including Expedited Debris Flow Modeling and "Capacity Only" 2D Sediment Modeling.