Base Linear Structures (2D)

Base Linear Structure (2D) objects are line objects used as part of the mesh generation process carried out when undertaking 2D Modelling. The lines represent structures such as walls and weirs with a specified porosity and height which are taken into account during the 2D simulation process. Note that a Base Linear Structure collinear with the boundary of a 2D zone, will override the boundary condition of the 2D zone along the coincident portion of the boundary. The coincident portions of the wall are considered infinitely high, regardless of any crest level specified.

Base Linear Structure (2D) objects can be imported via the Open Data Import Centre or from AutoCad DWG. Lines can also be digitised directly on the GeoPlan Window.

Base Linear Structure (2D) parameters are edited in the Base Linear Structure (2D) Grid Window of the Lines Grid or the Base Linear Structure (2D) Property Sheet.

In this version, the following types of structure can be modelled: walls, weirs (thin plate weir or broad crested weir) and user controlled (flow through the structure is controlled by a user defined head-unit flow curve).

Sluices and bridges along the length of the linear structure can also be modelled by associating Sluice Linear Structure (2D) and Bridge Linear Structure (2D) objects with the base linear structure.

Breaches in the linear structure can be modelled by defining vertical movement of points along the structure via Real Time Control. See Modelling Breaches in Banks and Linear Structures for details.

Technical overview

Collapsing walls

It is possible to set parameters for the Wall structure type which will result in the full or partial removal of the wall during a simulation depending on criteria based on the results of 2D mesh elements adjacent to the wall. The removal of the wall represents the collapse of the wall.

Sampling elevations from a ground model

Level data for a base linear structure with Crest level set to Irregular can be updated by sampling a Ground Model. Elevations at existing vertices can be updated and new vertices inserted between existing vertices.

See Updating Network Objects from the Ground Model for details.


Flow crossing the linear structure is monitored and output in the Line Results. The flow direction is determined using the same convention used for river sections, in which the first point on the line structure is assumed to be on the left hand side when facing downstream.

Base Linear Structure (2D) Data Fields

Sluice Linear Structure (2D)

Bridge Linear Structure (2D)

Modelling Breaches in Banks and Linear Structures

Linear Structure Results Data Fields

Lines Grid

Property Sheets

Creating 2D Meshes

Open Data Import Centre

Importing from AutoCAD DWG

Digitising Network Objects

Editing Network Object Geometry