Link references

Link-lines are used to connect 1D river networks and 1D urban networks. They are created using the 1D Urban - 1D River linking tool. This tool is accessed via the 1D Urban/1D River button on the 1D Urban Build tab.

The tool enables you to specify links between the active river and urban networks to ultimately create a link-reference (*. isl) file. This is a comma-separated text file.

Technical details about link-references are provided below.

Recommendations vs Requirements

Your river network must be loaded and active to use this tool. Your urban network does not need to be loaded, although we highly recommend to also load this and set active to take full advantage of the '1D Urban / 1D River' Linking Definition Tool. We also advise both networks are georeferenced.

If the urban network is not loaded into Flood Modeller, the tool will allow you to browse to an urban network file (and then automatically fill the urban nodes available for connecting as rows in the table). You can then proceed to 'Start linking', using the map to select the appropriate river node(s). 

Alternatively to using the map to select your river node(s), the tool allows for the node label to be typed directly into the field. Please note that it is highly advised to instead select your river node(s) via the map as the label must be exact, including case. The tool will not catch any mistakes or typos made by manually typing into these fields, and if the node label is incorrect, the error will not be discovered until run-time (i.e. your simulation will fail).

Link-reference Types

The '1D Urban / 1D River' Linking Definition Tool provides a table that will automatically populate with the urban nodes that are available for connection to river nodes.

You can connect junction, flow divider or outfall nodes in your urban network to any river section, replicate or interpolate node present in your river network using the ‘Flow to river, stage to urban’ link-reference type. The river section (or replicate/interpolate) must have a positive 'Distance to Next' specified, i.e. must not be at the end of a reach or at the location of a structure.

This link-reference type passes the calculated flow at the urban node to the connected river node, for example outflow pipes from an urban drainage system joining a river.

If multiple urban nodes are connected to a common river node using this link-reference type, the calculated flow at the urban nodes will be summed and passed to the connected river node. The stage calculated at the river node is passed to all connected urban nodes.

Advanced Link-reference Types

Additionally or alternatively to the default link type of 'Flow to river, stage to urban', you can connect a junction, flow divider or storage node in your urban network to a unique HT boundary in your river network using the ‘Flow to urban, stage to river’ link-reference type. This passes the calculated flow at the HT boundary to the connected urban node. Note that you cannot connect two urban nodes to the same HT boundary. If using this linking method, you will also need to allow inflows to the connected urban nodes. This can be any dummy time series - the values will be overwritten. Set a dummy inflow to your nodes in the following way:

Do I need to use the tool?

No - your link-reference file can be created in text editor and given the .isl extension.However, we highly recommend you instead use the tool to ensure all aspects of the file are in the correct format.

.isl datafile format

The 1D-River-Urban link (*.isl) file is a comma-separated text file, which is described by the following format

Preliminary notes

1. Only items within the [Links] section are read by the computational engine
2. Fields are comma-separated
3. Lines beginning with "#" are ignored
4. The column order is fixed, as described in the table below; note that the column headers are written by the linking tool, but are not read by the computational engine (since they begin with the comment separator “#”)

Datafile Format

Notes

Valid connection type names are:

1. Q2I (or synonym H2S) – calculated discharge (flow) is applied to 1D River from 1D Urban; 1D River returns calculated water level (stage) to 1D Urban
2. H2I (or synonym Q2S) – calculated water level (stage) is applied to 1D River from 1D Urban; 1D River returns calculated discharge (flow) to 1D Urban

Only the following types of node combinations are allowed to be linked

1. Type Q2I:

   1D River node type	1D Urban node type
   CHANNEL type (with distance to next section >0)	JUNCTION
   CHANNEL type (with distance to next section >0)	DIVIDER
   CHANNEL type (with distance to next section >0)	OUTFALL

2. Type H2I:

   1D River node type	1D Urban node type
   HTBDY	JUNCTION
   HTBDY	DIVIDER
   HTBDY	STORAGE UNIT

If the specified node labels are missing or invalid, they are treated as follows:

• missing/invalid 1D Urban node name – ignored; warning issued
• duplicate 1D Urban node name – simulation fails with fatal error issued
• missing 1D River node name – line ignored; no warning issued
• invalid 1D River node name – ignored; warning issued