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1. Open SOBEK and add a new 'Flow 1D Model' from the 'New Model' button.
2. Take a moment to explore the project explorer and see what components make up a Flow1D model. (If you don't know what the project explorer is, please review these terms here)

3. To build a network you will need to open the central map by double clicking on network in the project explorer. If you have opened the central map, the ribbon will show the contextual Map tab (in green). In the Map tab, you can build a network with the tools in the Network group. Explore the icons in this group by hovering above them and reading the popup menu.

   
4. Create a network with the 'Add new branch' tool. Draw one branch. Two nodes are automatically created as well.
5. You should now see the something like below in your network. If your network looks differently (too many branches, or curved branches), simply select the branches and press 'Delete' in your keyboard to remove the branches and try again.
   
6. Next, we're going to change the coordinates of the nodes. Select a node. In the properties window, change the x, y coordinates and name of the nodes manually to (Name: Begin, x:0 m, y:0 m) and (Name: RiverEnd, x: 350000 m, y:0 m).

7. Add a second branch attached to the first one. Do this by using the 'Add new branch' tool and starting the branch at the end of the last node. Change the coordinate of the third node to (Name: LakeEnd, x:380000 m, y:0 m).

   Info

   If the branches are attached, the node will turn solid green. If this is not the case, you will see two nodes - possible close to each other - with white centers. The white centers denote that it is an end-node, i.e. it is only connected to one branch. This might happen if you clicked to far from the node you want to connect to, or if snapping is not enabled. To enable snapping, press S on your keyboard. Alternatively, you can merge nodes by selecting the new node and editing its coordinates. Nodes will merge automatically if their coordinates are exactly the same.

8. To get an overview of the branches in the model, use the Map explorer to navigate to the flow model/input/network, right-click on branches and select 'Open Attribute table'. You can do this for every component in the model. For example, try to open the attribute table of the nodes in the same way. You should now have a network with two branches and three nodes. 

Add cross-sections

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cross-sections cross-sections

1. To add a cross-section, use the 'Add CrossSection (ZW)' tool and click anywhere on a branch. You can change the name and location (chainage) of a cross-section via the Properties window or its attribute table. In this way, a one cross-section at the beginning of the branch and one at the end of the branch.

2. To define the cross-section definition, double click on the cross-section. Change the cross-section to resemble the compound channel. Use the following dimensions:

   Parameter	Value
   B1	50
   B2	70
   h1	3.5

   To use the same cross-section multiple times, you will need to share the cross-section definition. Still in the cross-section view, click  'Share this definition'. If you define a new cross-section somewhere in the model, you can now use the shared cross-section.

   Info
   The ZW profile is per definition symmetrical. Note that other types of cross-section exists as well, viz. 'YZ' and 'XYZ', that can be assymetrical as well. However, only ZW profiles can be used in combination with morphology.

3. To impose a slope, change the Level Shift. By imposing a Level Shift, the cross-section definition is uniformly lowered or heightened. Impose a slope of 0.15 m/km by setting the level shift of the upstream cross-section to '50' and the downstream cross-section to '-3.5'.

4. To see if your model is set-up like you want it, let's make a sideview. To do this, click on the 'Add route' tool in Ribbon/map/network. Next, click on the beginning of your network first, and then on the end of your network. A route will automatically be generated.

   Info
   You can manage routes and change their names in the 'Region window'. By default, the region window is located in the same place as the Toolbox (right upper side). Click on the region tab to switch to the region window. Routes are locates under network.

5. In the Ribbon ('Map' tab, 'Network coverage' group), select your route (We have renamed it to 'EntireModel') and click on the sideview icon to generate the sideview.

   

6. The result should look like this:
   

Add computational grid and boundary conditions

1. To generate a computational grid, right click on Computational grid in the Project explorer and select Generate computational grid nodes. Choose to generate new grid points with the settings: a preferred length of 500 meter and no special locations.

   Info
   SOBEK uses a 'staggered grid' for the numerical solution of the flow equations. For more information, check the D-Flow1D technical reference manual, chapter 'Numerical Concepts (1D)'. In staggered-grid terms, the computational points you just generated are 'water level points'.

2. Boundary conditions can be added in the project explorer. Double click on the directory 'boundary conditions'. In the central map, the 'boundary data' table will open. In this table, select the node 'Begin' and

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1. set the boundary condition to Q(t): Flow time series. Next, select the 'EndLake' node and set the boundary condition to 'H: Constant water level'. Do not set a boundary condition for the 'EndRiver' node!

2. In the Project explorer, you should now be able to collapse the 'boundary conditions' directory. Edit the boundary data by double clicking a boundary condition. In this way, set the 'EndLake' boundary condition to a constant water level of 2.45 m. Set the 'Begin' boundary condition to the following timeseries by simply copy-and paste.

   Info
   Copy-paste might fail or result in irregular results if your system has a different time format. If copy-paste fails, use the 'Clipboard import' instead and manually set the input time format.

   Time	Discharge (m3s-1)
   01-01-05 00:00	107
   02-01-05 00:00	107
   02-01-05 06:00	138
   02-01-05 12:00	200
   03-01-05 00:00	368
   03-01-05 12:00	599
   03-01-05 18:00	675
   03-01-05 21:00	698
   04-01-05 00:00	706
   04-01-05 03:00	698
   04-01-05 06:00	675
   04-01-05 12:00	599
   05-01-05 00:00	368
   05-01-05 12:00	200
   05-01-05 18:00	138
   06-01-05 00:00	107
   07-01-05 00:00	107

Add initial conditions

1. Your model should actually already be able to run by now, using the default value for the initial condition. Run the model by clicking 'Run all' in the Ribbon/home tab! After the calculation has run, open the sideview (see 'add cross-sections'#cross-section step 4-6) to check the result. Slide the
2. However, in many cases it is advisable to set an initial condition.

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