Grading a new channel meander, backwater channel or side channel for a stream, wetland and aquatic habitat restoration projects can be quite tedious. This is especially true when you include more advanced designs containing riffles, pools and a meandering thalwag. There are many ways to approach this type of design project in Civil 3D. This post will outline one of the more simple methods for getting some quick volume calculations and a preliminary design
STEP 1: Begin by opening a file containing your EG (Existing Grade) surface. For preliminary excavation quantities I chose to use a rough lidar surface.
In this example the student was not familiar with the newer Civil 3D ribbon menus so I had them turn on the classic pull downs. Do this by typing "menubar" in the command line. Set the Variable to (1) for pull-downs.
STEP 2: Rough in you your new channel alignment with the polyline tool.
STEP 4: Select your feature line just created and right click to select the Elevation Editor. You will see the Elevation Editor as it appears to the right.
STEP 5: Enter the desired tie in elevations at the upstream and downstream locations of your of your new feature line (new channel alignment). These are the actually surface elevations from your EG surface at these locations.
STEP 6: Manually calculate your slope using the upstream and downstream tie in locations from step 5. Keep in mind that this will create a very simple stream channel profile with no pools or riffles. This will not make the fish happy. In the future try to create more advanced stream profiles. Enter the calculated slope in the Grade Back column or the inverse in the Grade Ahead column. Your feature line now represents the intended designed slope of your new channel and now becomes your channel thalwag.
STEP 7: Use the stepped offset tool to create the toe of slope on each side of your channel thalwag. In the pull down menu loaded earlier select GRADING > EDIT FEATURE LINE GEOMETRY > STEPPED OFFSET. Or in the ribbon menu select the stepped offset button in the grading menu. Use the feature line (thalwag) with set elevations and slopes to offset the left and right toes.
STEP 8: Open the "Grading Creation Tools" pane from the ribbon menu or go to the pull down menus and select GRADING > CREATE GRADING. You will see the Grading Creation Tools pane as it appears to the right.
STEP 9: In the Grading Creation Tools pane set your target surface to your EG Surface. It is the second button from the left (First Highlighted button in image).
STEP 10: Select "Grade to Surface" (Second highlighted area in image)
STEP 11: Create Grading by using the radio button (third highlighted button in image) and select "Create Grading". The commandline will prompt you to enter design criteria
STEP 12: There are many ways to continue from this point. Since this is an "easy" tuturial I have chosen to procede as follows. Explode the grading elements or trace using "3p" command so you can add them as breaklines later on. These lines are now the tops or daylight lines of your new channel.
STEP 13: Create your PR (Proposed) Surface by hgoing to your toolspace and creating a new surface.
STEP 14: Under the PR surface definitions add the thalwag, toes and tops of your new channel.
STEP 15: Adjust your PR surface style to turn on the TIN. This must be done for the next step.
STEP 16: Your new surface should look similiar to the image below. Not the stray TIN surface lines outside of your intended designed stream channel. You are going to have to deal with these as they impact your cross sections and volume calculations. There are a few ways to clean the surface up. I am going to show you how to "Delete" them. Under Toolspace>PR Surface>Definitions right click on Edits and select "Delete Line". A good tip is to delete only a few at a time. If the surface is too large selecting all of them at once could crash your software.
STEP 17: It time for your volume calculations. Go to your analyze tab and select volumes. This will bring up your composite volumes panorama. The first button on the top left will create a new volume entry. Once the new volume entry is created set the base surface to EG and the comparison surface to PR. You now have preliminary volume calculations for your new channel.
In the future, I will outline how to create dynamic channel designs appropriate for multiple iterations.
