Storage Compensation during Merging and Pruning

When you merge or prune sections of the network, storage will be lost from conduits and nodes that are removed as part of the process. This loss of storage may cause unexpected results, with the network model showing flooding at some nodes when observations show that flooding does not take place.

InfoWorks ICM provides a method for retaining this below ground storage in the model after merging or pruning.

The software will carry out calculations to work out the amount of storage lost to the network during the merging or pruning operation, and apply that storage as Manhole Additional Storage at the nearest upstream and/or downstream manhole node.

You decide how this additional storage allocation is managed using options accessed on the Simplification Options Dialog.

Additional storage applied to nodes as a result of merging or pruning is included in the Chamber Additional Storage: Simplification and Shaft Additional Storage: Simplification fields for the nearest upstream and/or downstream manhole node.


The process has two parts. You must first set up the parameters used for storage compensation, and then carry out the merging or pruning on the network.

Setting up

To set up the parameters:

  1. With a network open, select Simplify | Simplification options from the Model menu. This displays the Simplification Options Dialog.
  2. On the Network Simplification Page, click on the Define button for either merging or pruning. This displays the Merge Dialog or the Prune Dialog.
  3. On the Include Page, decide what storage to re-allocate during the merging or pruning process
  4. On the Distribution Page, choose where the storage is re-allocated. You can choose to split the storage between upstream and downstream manholes, and to further split the storage between shaft and chamber of the manhole. See Choosing Where to Apply Additional Storage for more details on these options.
  5. By default the additional storage is added to any existing additional storage on the chosen nodes. This would normally make sense. However, you can un-check the Add Area Contributions to Existing and replace existing data if required
  6. When pruning, there are further requirements that can be made to the selection on the Selection Refinement Page. These are fairly self-explanatory

Merging or Pruning

See the help topics for Merging and Pruning for details of the steps involved in each process.

In basic terms the process has two parts:

  1. Setting up parameters for the process in advance. These include the parameters for storage compensation
  2. Carrying out the actual merging or pruning

InfoWorks ICM applies additional storage in the Shaft Additional Storage: Simplification and Chamber Additional Storage: Simplification field of the upstream and/or downstream nodes.

Storage Compensation