The first tab is used to refine the selection done with the mouse on the graph or the treeview of the network by allowing to:

• Selection of the beginning and ending Reaches within respectively the Upstream Reach and the Downstream Reach of the selection, to focus on only part of it.
• Selection of the beginning and ending sections within respectively the Upstream Reach and the Downstream Reach of the selection.
• The section type which will be impacted by the actions of automatic modeling (minor bed, minor-medium bed, major bed).