Link references
    • 21 Sep 2022
    • 4 Minutes to read

    Link references


    Article summary

    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.

    LinkedComponentsimagesrivertourbanlinktool.PNG

    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

    Name

    Description

    Required?

    Comments

    1D River Node

    Label of linked 1D River node

    Yes

    See note 3

    1D Urban Node

    Label of linked 1D Urban node

    Yes

    See note 3

    Connection type

    “H2I” or “Q2I” (see note 1)

    Yes

    See note 3

    1D River Node Type

     

    No

    Reference only

    1D Urban Node Type

     

    No

    Reference only

    Easting

    Horizontal coordinate

    No

    Reference only

    Northing

    Vertical coordinate

    No

    Reference only

    Description

     

    No

    Reference only

    Perimeter

    Effective perimeter of 1D Urban node for free inflow discharge

    Only used for H2I link; for free discharge into 1D Urban

    If zero or negative, then free discharge from 1D River to 1D Urban via an H2I link will not occur (effectively sets Q=0)

    cd

    Weir coefficient for free discharge into 1D Urban node

    Only used for H2I link; for free discharge into 1D Urban

    If set zero or negative, a default value of 1.2 will be used

    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

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