AVRas Version 2.2  - an ArcView extension to link with HEC-RAS

HEC-RAS is a computer program distributed by the Hydrologic Engineering Center of the US Army Corps of Engineers in Davis, CA, for computing water surface elevations in rivers and streams.   It is based on input information about the morphology of the stream in the form of cross-sections located at intervals along the stream course, and related information about the roughness of the stream and the discharge of water through it.  Using these data, HEC-RAS determines the elevation of the water surface above mean sea level at each cross-section.  AVRas can be used to set up the cross-sectional information for HEC-RAS assuming the user has a TIN of the stream morphology available.  Once the water surface elevations are determined, AVRas can be used to take the output file from HEC-RAS and plot the resulting flood plain in ArcView.  AVRas requires ArcView GIS Version 3.0a or later and the ArcView 3D Analyst Extension.  For more information on how to use AVRas, see the training document.

Four files are distributed in the avrasfiles subdirectory on this CD:
georasav.avx   - the avras extension.  It should
      be placed in the $AVHOME\ext32
      directory.
avras.cnt   - avras help file TOC
avras.gid   - avras help file GID
avras.hlp   - avras help file

The three avras help files should be placed in the
$AVHOME\help directory.

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! AVRas is an unsupported extension !
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For technical questions and comments regarding
AVRas, contact:

Dr. Dean Djokic
ESRI
380 New York St.
Redlands, CA 92373
tel. 909-793-2853 ext. 1072
fax. 909-307-3014
email. ddjokic@esri.com

For questions regarding purchasing of ESRI
products contact your local ESRI distributor
or regional office.

What is new in AVRas 2.2

AVRas 2.2 is a major update from the previous AVRas release (version 1.2). The key changes were made to make AVRas compatible with the RAS GIS output file format generated by RAS 2.2, and to make the AVRas functionality matching the functionality found in the HEC’s HEC-GeoRAS (ARC/INFO version).

AVRas 2.2 is the last version of AVRas that will be developed and distributed by ESRI. ESRI has upgraded the original version of AVRas to meet the requirements by HEC and once the beta process is over, ESRI will turnover the development and "ownership" of AVRas to HEC. AVRas (with a different name) will become an "officially" developed and supported HEC software product. The distribution and support of AVRas will be managed by HEC in the same way all their other software products are managed. This release of AVRas (version 2.2) is part of the BETA program for the final release to HEC. Your input is thus even more important than before, since we would like to deliver to HEC a bug-free and functional application that the whole water resources community can immediately use and enjoy. There have been several major changes since AVRas 1.2. These changes are both functional as well as in the "ease-of-use" domain. We are not planning to add any further functionality at this stage (unless you come up with some GREAT ideas). Any requests for further functionality will be passed-on to HEC, and they might decide to include them in their later releases. Any identified bugs will be fixed immediately. For bug fixes contact Dr Dean Djokic at ESRI at ddjokic@esri.com.

The following modifications have been implemented in AVRas 2.2 (since release of AVRas 1.2):

• Post-processing is made compatible with the new format of the RAS GIS output file produced by RAS 2.2. Previous file format is still supported, so any RAS GIS output file will be successfully processed.
• For RAS GIS output file generated by RAS 2.2, AVRas will generate the 3D cross-section theme (if data are available in the output file) and the stream centerline theme based on the RAS output. Neither of these themes are used in the post-processing, but could be useful for quality control.
• A water depth grid will be created for each processed water surface profile.
• The user can select which water surface profile to process (instead of all being processed at once).
• Several utilities have been developed to streamline the data input:
• Creation of (empty) stream centerline shape file with proper data structure.
• Creation of (empty) flowpath shape file with proper data structure.
• Tool for defining or modifying the stream and reach Ids (attributes in the stream centerline theme).
• A function for defining or modifying the flowpath type (attribute in the flowpath theme).
• Use of tags associated with theme is expanded, so now each theme used in AVRas has a dictionary associated with it, allowing more flexibility in theme management. Tools for dictionary management have been provided (display, modify, and remove).
• Global variables are not used any more, anywhere in AVRas. Instead, persistent project information is stored with a dictionary associated with each view used in the AVRas project. The same tools for theme dictionary management are available for view dictionary management.
• AVRas is made aware of Spatial Analyst, that is, if Spatial Analyst extension is loaded, more efficient post-processing techniques will be used, potentially significantly speeding-up the floodplain delineation and water depth grid determination. If Spatial Analyst is not loaded, AVRas will use 3D Analyst functionality only.
• Help files have been updated to reflect all the changes.

Known unresolved issues:

• More than 500 points in a cross-section. For complex terrain TINs, it is possible that AVRas will generate more than 500 points in a cross-section. AVRas generates cross-section points (3D) at cross-section cut line vertices and at all the locations where the cross-section cut line intersects the edges of terrain TIN triangles. The 500 points is a limit for the number of points in a cross-section that RAS numerical engine can manage. The geometry GIS import option will allow all the points to be imported into RAS, but when attempting to run the analysis, an error message will be generated stating that the maximum number of points has been exceeded at the "offending" cross-section, and the analysis will fail. At this point, an automated solution for "weeding" out the extra points has not been implemented. The user can manually eliminate the extra points using the standard RAS cross-section editing tools.
• Water surface TIN interpolation when "staggered" cross-sections are present (confluence). When cross-sections at two or more merging streams are staggered, the water surface TIN interpolation will be influenced by water surface elevation at all the cross-sections in the proximity. This can produce a water surface TIN that will not be correct in that local region, which in turn can potentially generate incorrect floodplain polygon. This will occur only if the flood extends in the area impacted by the ends of the staggered cross-sections. Such situation indicates a potential problem in the assumptions of one-dimensional flow (the basis for RAS analysis) and the user needs to make the evaluation whether the hydraulic results are acceptable or a two-dimensional hydraulic model needs to be used to model the confluence. If the hydraulic modeling results are acceptable, but the automated flood delineation in the area of confluence is not, the user will need to manually change the floodplain polygon to match their interpretation of the modeling results.