Data Extraction for HydroCAD

This lesson covers extracting watershed data for HydroCAD stormwater modeling using Carlson Hydrology. The goal of this functionality within Carlson Hydrology is to automatically extract the sub-areas needed by HydroCAD to do its stormwater modeling. There are 3 main considerations to prepare a dataset for extraction:

1. Watershed (subcatchment) delineation, with either:
   1. Longest flow path and average slope information for Curve Number/Lag method, or
   2. T_c with sheet, shallow, and channel flow information defined for TR55 method
2. Delineation of Hydrologic Soil Group (HSG) with:
   1. HSG boundaries defined on one layer, and
   2. HSG labels on another layer
3. Ground cover delineation, with:
   1. Each type of different ground cover area defined as closed polylines on specific layers, corresponding with entries in the hydrocad.rcl library

Let's get started.

1. Click the Windows desktop icon for Carlson to start the program.
   • If you get the Start Page, pick Open Files.
   • If you get the Startup Wizard dialog box, click the Browse button.
   • If you are taken directly into CAD, click File -- Open.
   Browse/navigate to the default folder location of C:\Carlson Projects and open the HydroCAD_Tutorial.dwg file. Use the File -- Save As to save a copy named HydroCAD_Tutorial-A.dwg. Completing this tutorial will alter the drawing file and by renaming the file from the start, you'll keep the original file intact (allowing you to run through the tutorial a second time if desired). This is also a good practice to keep when working on drawings from 3rd parties.
2. Activate the Hydrology menu via Settings -- Carlson Menus -- Hydrology Menu. The entire process described herein is essentially a layer-based process, meaning that it is the drawing layers that everything is placed upon that makes the process work. So before going any further, take a look at the dialog box in which those layers are defined. Issue the HydroNet -- Define Watershed Layers command to display a dialog box similar to that shown below:
   NOTE: If you have a predetermined grouping of watershed layers you wish to preserve, click the Save button to save your previous layers to a named *.RCL file. The step to follow will replace the existing layers with established HydroCAD default layers.
   Click the Load button and load the hydrocad.rcl file as shown below and click Open when ready:
   
   Once loaded, enable the HydroCAD radio button at the top of the dialog box. Any layer names in this dialog box can be changed to whatever you like, but the linework created must use the layers you decide on. A helpful trick is to highlight the layers in the list that you think you will need for the project at hand (using standard Windows Shift+click and/or Ctrl+click functionality) and then click the Create Layers button which would display a dialog box as shown below:
   
   The layers will be created for you thereby eliminating the need to type them all in by hand, and also avoiding typos that will cause the data extraction to fail. Dismiss the Create Watershed Layers dialog box and click the OK button to dismiss the Define Watershed Layers dialog box. Now that the layers are established, you can focus on creating the geometry in the drawing.
3. In this example drawing, sample subcatchments (watersheds) for HydroCAD have been delineated for us with polyline geometry on the following layers:
   • subcatchments
   • subcat_numbers
   • subcat_flowlines
   • longest_flow_paths
   These subcatchment delineations can be done using any process desired... looking at the contours, looking at aerial photos, whatever method is most useful and comfortable is fine. It is the end result of linework that delineates the areas that are needed... the method to get them is inconsequential. The example data for this project is shown below (colors modified for clarity):
   
   If there is a surface (TIN) for the project site (as there is for this example), Carlson Hydrology can greatly aid in the process of delineating watersheds (subcatchments) and determining the longest flow path for each subcatchment. These tasks are accomplished by issuing the HydroNet -- (or Watershed -- ) Watershed Analysis command. When prompted:
   
   Specify the surface model file as indicated above and click Open when ready. A "docked" dialog box similar to that shown below appears:
   
   Set the various toggle options as cited above and click the Draw button when ready. The following should be displayed (layers frozen for clarity):
   
   Once the watersheds and max flow lines are drawn, you can make decisions on them:
   • Are there too many?
   • Are there too few? etc?
   Adjusting the Rainfall value and/or clicking the Settings button can assist with the desired delineation.
   
   Tip: To combine several watershed perimeters into one, use the Draw -- Shrink Wrap Entities command with the Bound method. You would pick the combination of watersheds, and a new boundary would be drawn around them.
   
   For the purposes of this tutorial, let's use the polyline geometry already established for us. Click the Undo button (next to the Draw button) to remove the Watershed Analysis results from the drawing. Ultimately, you should be left with a closed polyline for each watershed, labeled with a designator and containing a single 3D polyline within each watershed representing the longest flow path as shown below (certain layers frozen for clarity):
   
   Click on the Exit button to dismiss the Watershed Analysis dialog box.
4. Soil conditions (Hydrologic Soil Groups or HSG for short) must also be properly delineated. What you'll need, ultimately, from whatever source(s) you have is a drawing with:
   • the soil groups drawn as polylines, all on one layer, and
   • the HSG types (A, B, C, or D) labeled within the areas on another single, specific layer.
   NOTE: The soil areas must be closed, but do not have to be individual specific closed polylines. The software will run a "boundary polyline" (bpoly) on each area to "close" it. The soils information can come from a shape (SHP) file such as that from USDA - NRCS or , from a ground soils survey, from digitized plans... it doesn't matter. The only thing necessary is the linework and labels such as those shown below (certain layers frozen for clarity):
   
5. Finally, ground cover. In standard use, this term applies only to the ground cover which is independent of the underlying soil group(s). Neither layer equates to a specific Curve Number (CN) value which can only be determined after we analyze the intersection of these layers. The actual CN value(s) will be assigned by HydroCAD after this analysis is complete. Once again, with whatever method you like, create closed polylines on the various ground cover layers as illustrated below:
   
6. Now that you've drawn all the watershed and site data, we can start to extract the information we need for hydrologic analysis. Issue the HydroNet -- HydroNet Explorer. When prompted, create the HydroNet file as cited below and click Open when ready:
   
   In the resulting "docked" dialog box, pick the Settings (Gear) button as highlighted below:
   
   In the Settings dialog box:
   • on the General tab, set the click the Set to set the Surface File we used earlier as shown below:
     
     Set the other values as shown.
   • on the SubCatchment tab, set the T_c Calculation Method to Curve Number/Lag as illustrated below:
     
     Also, clear the box to Process Curve Numbers/Runoff Coefficients as they will be determined in HydroCAD.
   • Review the other tabs of settings as found in this dialog box and click OK when ready.
7. You are ready for the data extraction to be performed and the results exported to HydroCAD but we must make sure all pertinent layers are On/Thawed. Issue the View -- Thaw/On All Layers command so the data can be processed. From the main HydroNet docked dialog, click the Update (Up Arrow) button as illustrated below:
   
   A secondary dialog box appears with the options for the update. Select the options as shown below and click OK when ready:
   
   The subcatchments are listed in the HydroNet Explorer and HydroCAD (if installed), is launched. Double-clicking on any subcatchment name brings up a dialog with its data as shown below:
   
   NOTE: The same subcatchments now exist in HydroCAD, ready for any further analysis and/or reporting.
   Click the Edit button next to the Area value shows all of the sub-area statistics as illustrated below:
   
   Click OK to dismiss the Sub Areas dialog box and then click OK to dismiss the Subcatchment dialog box to return to the HydroNet Explorer docked dialog box. Click the Exit (Doorway) button to dismiss the HydroNet Explorer docked dialog box.
8. Double-clicking a subcatchment in HydroCAD opens the Hydrograph and Summary report windows as summarized below:
   
   
   Project reports can also be generated for Nodes, Areas and Soils (among others):
   
   
   
   Any changes made in the drawing can instantly update the data in HydroCAD simply by picking the Update button.

This completes the tutorial: Data Extraction for HydroCAD.