# Breach Modelling in InfoWorks ICM

A recent addition to InfoWorks ICM is the ability to add time-varying geometry using RTC.  The time varying geometry can be applied to:-

• River Reaches (left and right bank used as a 1D-2D link or 1D-1D link)
• Inline Banks (used as a 1D-2D or 1D-1D Link)
• Base Linear Structures (2D)

The time-varying geometry can be used to represent a user-defined breach in these structures.  Each of the above structures has a table where the X,Y and elevation values are set.  This is where we add the starting point of our structure or bank.  As well as this, on the furthest column to the right, is a column called RTC Definition.  This is where we would assign some Real-Time Control (RTC) to represent how our elevation values are going to vary in time. Below is a screenshot from a 2D Base Linear Structure where points 4 to 7 are going to be varied based on the RTC definition RTC1. The next step is to set up the RTC using the RTC editor.  The only RTC definitions that can be used to control points are:-

• Tables
• Variables

For example, we could set up a Range dependant in which we set a Time input.  Then we set up a Table which uses the Time Range as input and outputs either ‘Height above datum’ or ‘Depth’.   These are defined as below:-

Height above datum: level of point is set to the height value defined in the RTC definition

Depth: level of point is set by subtracting depth value from the elevation specified at each vertex.

Below is an example of the potential RTC.  In this case the level will be slowly reducing representing a breach.  We could also increase the elevations if required to represent building up of an embankment. Once the RTC is defined and the Banks/Inline Banks/2D Base Linear Structures are set up to reference the RTC then the time-varying geometry will be represented within the simulation.

There are a couple of limits in how much the elevation can vary although in reality these would be practical limits too:-

• In the 1D network, the elevation of a vertex will not be set below the object that the river banks abuts.  This will either be the lowest level of a storage area, the lowest cross-section level for a river reach, or the elevation of a 2D element.
• In the 2D Network, the vertex elevations are used to calculate the new elevations of the faces that the form the linear structure (the flow calculation through the faces is based on the face level, not on the level of the vertices).  Face elevations will not be set below the level of the adjacent elements.
• During the simulation, bank/crest levels may be adjusted to ensure that the points are not below the adjacent 2D elements.  However, any depth setting is still based on the level specified on the network object property sheet.
• When modelling two river reaches with adjoining banks, the banks and the breach are merged.  If the adjoining banks are not identical, the merged bank uses the points and RTC from both banks to form a composite.  In the case of coincident points where only one of the points has RTC, then that RTC will be used.  In the case of coincident points where both points have RTC, only one of the RTCs will be used.

Results output can then be used to show the time-varying geometry, this can be viewed in tabular format: Graphs representing elevation values through time: or long sections in the case of 1D and 1D-2D time-varying geometry and 3D views: The time-varying geometry functionality will allow the modeller to add user-defined breaches into 1D, 1D-2D and 2D allowing Infoworks ICM to be used for breach modelling.  Animations such as the following can then be created from the output. 