The properties of Branches are specified under the General tab. The lower part of the dialogue window contains a list of all Branches in the River network. Select a Branch from the list and specify the properties.
Definitions
Connections
Edit coordinates of vertices
Load shape
Branch name
A Branch can be given any name.
Topo ID
Topo ID is an abbreviation of `Topographical Identifier', which refers to the same variable defined as part of the Cross section definitions. The cross section file offers the possibility to store several measurement campaigns (e.g. from different years or before and after the construction of a structure), and these are identified through different Topi ID’s. The main purpose of this is to enable simulation of alternative scenarios once the network has been configured. The topographical data used in a simulation is defined by the Topo ID.
Note that the String defined for the Topo ID must be identical to a Topo ID present in the cross section file for the actual river branch. If not, cross sections in the branch are not recognised and the calculation cannot start.
Start chainage
The chainage of the first point in the branch. To change this chainage, it is required to insert a User defined chainage point in the first point of a branch. The chainage can then be specified under the User defined chainage points tab (see below).
End chainage
The chainage of the last point in the branch. To modify this chainage, a User defined chainage point must be inserted in this last point of the branch. The chainage can then be specified under the User defined chainage points tab (see below).
Flow direction
The flow direction may be set as positive or negative, and indicates how the chainage definition is interpreted with respect to the flow direction. If flow direction is selected as positive, the main flow direction will be assumed to go from low chainages to high chainages in the river branch and the corresponding discharge will get a positive sign in the results (whereas the reversed flow direction will get a negative sign). If flow direction is selected as negative, the main flow direction is defined in the opposite way: positive discharge results will describe water flowing from high chainages to low chainages, and negative results in the opposite direction. This main flow direction is per default reflected with an arrow along the river on the map.
The default assumption is to define flow direction positive with increasing chainages looking downstream of the river. Hence, if a river has been defined with chainage 0 (zero) at the river mouth and chainages increasing upstream, the flow direction must be defined as negative.
The 'Flow direction' also controls the definition of the left and right sides of the river, which are important for the correct definition of cross sections: the sides are observed looking in the direction of the main flow:
· For a positive flow direction, the left and right sides are observed looking in the direction of increasing chainages
· For a negative flow direction, the left and right sides are observed looking in the direction of decreasing chainages.
Branch type
· There are three different Branch types:
· Regular. A Regular Branch is a ‘normal’ Branch consisting of a number of computational points defined from Cross sections. A minimum of one Cross section is required. The hydrodynamic simulation in a regular branch is based on a solution of the de Saint-Venant equations.
· Link Channel. A Link Channel is typically a short Branch used to connect a flood plain to the main river branch. Link channels do not require Cross sections to be specified but all parameters given in the Link channels dialogue (see below) must be specified.
· Routing. No cross sections are required. Only the flow is calculated and routing is a simplified hydraulic calculation. The concept of routing is basically the transformation of a hydrograph entering at the upstream end of a branch into a downstream outflow.
Information about Branches and their upstream and downstream linkages are provided.
In some cases it might be necessary to update the coordinates on the map view of the vertices of one or more branches.
When a specific branch is selected in the table and the “Edit coordinates of vertices…” button is pressed, a table-dialogue pops up. This table contains the X and Y coordinates of the points of the selected branch, which can be edited (copy and paste is also supported). No new rows can be added, nor deleted. When the update is done and OK is pressed, the map view is updated.
It is possible to import/load the shape of an existing branch directly. Select/activate the actual branch in the tabular view and Click ‘Load shape’, select the relevant shape file and choose the shape item that represents the branch.
Note: this functionality will only edit the shape of the active branch on the map. It will not create any new branch. Instead, it is possible to import and create one or multiple branches at once from a shape file. To achieve this, please see section Import from Shapefile.
