1. Below is an example 1D river reach model built in HEC-RAS and displayed in the HEC-RAS user interface:

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1 How Do I Import HEC-RAS Cross-Section Data? Flood Modeller allows you to read in cross sections defined in HEC-RAS models, automatically converting them to Flood Modeller 1D cross sections. The procedure for importing HEC-RAS data into a 1D network is as follows: 1. Below is an example 1D river reach model built in HEC-RAS and displayed in the HEC-RAS user interface: Example HEC-RAS model and selected cross section The cross section information is contained in one or many geometric files. These are text format files with file extension.g01,.g02,.g03, etc. 2. In Flood Modeller you can import these data into a new 1D network or append to an existing 1D network. To import into a new network you first need to start a new, empty network. In the main toolbar > Home tab click on New in the Networks section. You will be prompted to give your new network a name and browse to the folder where it will be saved. The new network will be added to your project panel and made active. The (empty) network table for your new network will be shown to the right of the map. 3. Right-click on the network table and select File > Import from HEC-RAS from the displayed menu, as shown below:

2 4. Browse to the HEC-RAS geometry file (e.g. *.g01 ). When the file is selected Flood Modeller reads the header of the specified file to determine the rivers and reaches (within each river) contained within the model. For each reach Flood Modeller defines a prefix name to be used to name all sections of the reach (this uses the first 3 letters of the associated river name and reach name). For each section the prefix is used with the HEC-RAS section name (usually a number) to define a Flood Modeller section name. The prefix data are displayed in a table in a new window, as shown in the example below. You can edit each prefix before proceeding to see a list of available cross sections. 5. Click OK to proceed to a list of available cross sections, displayed in a new window. You can select one or many sections from this table; use Ctrl or Shift keys to select groups of sections, or depress Ctrl and A keys to select all sections in the table. After selecting you can add these to your network by dragging from the table to the General row in the Network table (alternatively use Ctrl + C keys to copy sections then right-click on Network table and select Paste).

3 Select one or many cross sections and drag onto General row of new network (or use copy and paste into Network table) Note: Drag by depressing the left mouse button on your selected HEC-RAS sections and move the mouse cursor to the Network table, hover over the row below which you want to add the new sections (General row for an empty network) and release the mouse button. 6. Your network table and map view are populated with the selected HEC-RAS sections, as shown below. The sections will be georeferenced if the HEC-RAS sections include georeferencing information. In addition roughness data, distance to next section and any panel markers (where roughness changes across a section) will be extracted from the HEC-RAS data and included in your new 1D cross sections.

4 Double-click on a node to view the cross sectional data and then click the Plot button in the node properties window to view a cross section plot:

5 7. Save the changes to your network to store the new section information. You should then check the correct units are specified for the network, i.e. SI (metric) or US. These can be set at project level using the General settings (accessed from Home tab of main toolbar). Alternatively doubleclicking the General row of a network displays network level properties, which include the options to set specific units or default to the project level setting. In addition to displaying the 1D network as a series of icons, you can also show the section lines on the map by dragging the network from the Project panel onto the map (Tip: this sometimes requires two attempts to work). You can modify the section line colour by double-clicking the network layer displayed in the Layers panel (lower left corner of interface) and accessing the layer properties window. Furthermore if you know the geo-projection of your georeferenced data you can add base mapping to your map view by selecting a suitable mapping source from the Base Map menu (Home tab of main toolbar). The example below shows the HEC-RAS example displayed with Bing Hybrid mapping behind it: 8. To complete the construction of a Flood Modeller 1D network model from your HEC-RAS data you will need to add suitable boundary data to the upstream end (e.g. QT boundary) and downstream end (e.g. HT boundary) of the network.