I have a couple of questions. I appreciate if someone can help me.
1-How much terrain Resolution is enough for 2d hydraulic analysis? (In data provided with hecras 5 Beta version Muncie terrain has 5x5 feet cells and BaldEagleCrkMulti2D terrain has 20X20 feet cells)
2-How much terrain Resolution is enough for extracting cross section from terrain by using Hecgeo ras?
3-How can I import shape files into Hecras? I need to import a shape file represented my protected area into Hecras to draw 2d area(For designing levee).It is easy to bring shape file into the Ras mapper but I could not find the way which I can bring the shapefile in to geometry data window.
Terrain resolution all depends on what you are trying to accomplish. If you are doing a dam breach study, than you could use very coarse terrain (USGS 30m DEM), you just may need to burn in a channel. I have done many studies using Intermap topographic data which uses a 5m DEM for 2D floodplain modeling. You would want to make sure the resolution picks up all important features or else modification will need to be done to the 2D grid to incorporate the missing data.
For 1D modeling it is best to get actual survey if possible, but it also depends on what type of study it is. Often what happens is you get survey for the channel, use lidar for the floodplain, and incorporate them together into a DEM. The terrain resolution needs to be good enough to pick up critical features. If it does not, it will need to be supplemented with levee features and modifications to the channels
As for importing shapefiles, you bring them in the same way as an image and can digitize the 2D area. Another option would to use HEC-GeoRAS and import the 2D area as a storage area and convert it to a 2D area. If you don't have GeoRAS, you could first create a dummy 2D area, than extract the x and y coordinates of the 2D (in GIS) and import that into HEC-RAS using |GIS|Storage Area Outlines Table in the geometry editor window (needs to be less than 500 points though).
Firstly thanks for your complete response.You just made my day!
Secondly I have some other questions. I appreciate it if you respond me. :)
A-what do you mean by burn in the channel? Do you mean DEM reconditioning using Map Algebra and euclidean distance tool in Arcmap?
B- How can I make georeferenced channel terrain from survey data? (Previously, I used to simply draw the stream center line and input stations and elevation data in cross section data window without georeferencing (For 1D analysis). But now for combined 1d/2d analysis I think it is necessary to have georeferenced stream centerline and cross sections. I used baxter exapmle data (http://www.hec.usace.army.mil/software/hec-ras/downloads.aspx - Ras mapper example) and created georeferenced stream center line in Hec georas and imported it in to Hecras. I created 3 different xyz foramat csv files (Upper baxter, Lower baxter and tul creek) based on instruction provided on page 6-139 Hec ras user manual and imported them in to Hec ras. But unfortunately it does not work properly (The cross sections were connected through straight line instead of connecting through georeferenced stream center lines!) How can I fixed this problem?
C- Is it possible to incorporate channel and floodplain in Arcmap?( In combined 1d and 2d modelling with hecras manual page 19 explained how to combine channel and over bank terrain model but I like to know how can I do it in Arcmap)
D-How can I create georeferenced background picture for importing to hecras? (In muncie example provided with combined 1d and 2d ... manual, there is a JPG file and it's word file. I tried to create these files by using Arcmap ( Different ways like Exporting terrain file as Jpg file format or georeferencing Jpg file created by windows snipping tool and export it ) but the program does not allow me create the JPG file and the word.)
A - When I say burn, I mean combine the channel and overbank data. You can use ArcMap or other programs to combine the channel data with the other topographic data. If all you have is survey data then it is usually easiest to incorporate the data into the cross-sections in HEC-RAS using the Graphical Editor Merge Options.
B. It is always best to a have a georeferenced model. Since you have the xyz data for each cross-section you can go to the gis tool|xs cutlines table in the geometry editor and specify the xy coordinates for each cross-section (make sure it is left to right).
C. In arcmap, one option would to create TIN in arcmap from the survey alone and need to incorporate breaklines to connect cross-section to cross-section. Once this is done you could then mosaic the channel surface to overbank.