I want to simulating (steady state) discharge in a natural channel for various flowing depths. The channel has been digitized from GoogleEarth. The kmz file converted to shapefile. The channel is very sinusoidal in shape, with total length of 510 km, over a straight line distance of less than 200 km.
Using this shapefile or kmz file in HEC GeoRAS in ArcGIS 10.1 as pre-processor, I want to create RAS Layer for stream centerline. I mean without using DEM of TIN. Similarly, can I create cross-sections like this approach.
Help in this aspect will be highly appreciated.
Hi
If the shape file you have imported contains 'Z' (elevation data) too, i.e. its a polyline 3D, then you can directly use it in GeoRAS.
Usually, any existing shapefile can be used within GeoRAS by first creating a database with empty layers and then loading the shape file in the required feature, river, being the stream centerline feature in your case. You can look up this link for more information: http://web.ics.purdue.edu/~vmerwade/tutorial.html
Regards
Siddharth
Dear Siddharath, thanks for your kind reply.
Actually I do not have Z value, but I have used the simple shape file for developing RAS layer.
For this I created empty GeoRAS layer and initiated its editing, then right click on the existing simple shape in the dataframe and get its copy. Then again right click and select past. This process copies the shapefile to the empty GeoRAS layer with it shape length calculated in the database.
Thanks and regards
Hi. Thanks for clarifying.
In that case, yes, I think that creating cross-sections using this approach should be fine. But the spacing of the cross-sections would still need to be re-evaluated based on the google earth images as the bends would require more cross-sections.
You can also use ArcGIS online to directly add the world imagery within GIS to help in digitization instead of using Google Earth.
Siddharth
If you do not have a DEM you can create a dummy DEM in ArcGIS by creating a raster with a single elevation value. This will allow you to export your GIS data into HEC RAS. You will then need to add elevation data to your XS in HEC RAS, If the xs area is uniform there are some channel creation tools in HEC RAS that you can use to adjust the elevation data for many XS at once.
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