---
title: "General Tags | Technical Reference"
slug: "general-tags"
description: "Find the information on the general tags and the XML descriptions for the 2D solver. "
tags: ["2D modelling"]
updated: 2022-07-29T09:59:57Z
published: 2022-07-29T09:59:57Z
canonical: "help.floodmodeller.com/general-tags"
stale: true
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.floodmodeller.com/llms.txt
> Use this file to discover all available pages before exploring further.

# General Tags

Below is a description of the XML schema used by 2D Solver:

Tag **<ISIS2Dproject>**: required

Description The ISIS2Dproject tag is the root element of the XML input file and therefore encloses all other tags.

Attributes name (required) a description of the model

Elements <link1d> min=0, max=1

<logfile> min=0, max=1

<domain> min=1, max=Inf

Value none

Tag **<link1d>** min=0, max=1

Description The presense of a link1d tag indicates that the model is a linked Flood Modeller 1D-2D solver model and contains all the tags required for linking 2D domains to 1D domains.

Attributes none

Elements <link> min=1, max=Inf

<ief> min=1, max=1

<mb> min=1, max=1

Value none

Tag **<link>** min=1, max=Inf

Description The location and name of a link shapefile, normally containing a polyline indicating where the 1D and 2D domains are linked.

Attributes domain (op) used to instruct 2D solver which 2D domain this link should be applied to.

Elements none

Value a SHP file reference

Tag **<ief>** min=1, max=1

Description The locaion and name of the IEF file associated with the the linked 1D domain.

Attributes none

Elements none

Value an IEF file reference

Tag **<mb>** min=1, max=1

Description The location of a file to which mass ballance statistics will be written to.

Attributes frequency (op) the output frequency, in seconds, to write mass ballance information

Elements none

Value a mass ballance file reference

Tag **<logfile>** min=0, max=1

Description the location of a file to which run-time information will be written to.

Attributes none

Elements none

Value a log file reference

Tag **<domain>** min=1, max=Inf

Description The domain tag contains all information required for 2D solver to set up a 2D domain

Attributes domain_id (op) used to give each domain a human readable name

Elements <computational_area> min=0, max=1

<topography> min=1, max=Inf

<time> min=1, max=1

<run_data> min=1, max=1

<initial_conditions> min=0, max=1

<roughness> min=0, max=1

<boundary_conditions> min=0, max=1

<hydrology> min=0, max=1

<output_results> min=1, max=1

Value none

Tag **<computational_area>** min=0, max=1

Description The computational_area tag encloses tags used to describe the extent and composition of a 2D domain

Attributes none

Elements <xll> min=1, max=1

<yll> min=1, max=1

<dx> min=1, max=1

<nrows> min=1, max=1

<ncols> min=1, max=1

<active_area> min=0, max=1

<rotation> min=0, max=1

Value none

Tag **<xll>** min=1, max=1

Description The x coordinate of the lower left corner of the computational domain

Attributes none

Elements none

Value an X coordinate in meters

Tag **<yll>** min=1, max=1

Description The y coordinate of the lower left corner of the computational domain

Attributes none

Elements none

Value a Y coordinate in meters

Tag **<dx>** min=1, max=1

Description The chosen grid cell size

Attributes none

Elements none

Value a cell size in meters

Tag **<nrows>** min=1, max=1

Description The number of rows in the domain. The vertical extent of the domain will equal the the number of rows multiplied by the cell size

Attributes none

Elements none

Value the number of rows

Tag **<ncols>** min=1, max=1

Description The number of columns in the domain. The horizontal extent of the domain will equal the the number of columns multiplied by the cell size

Attributes none

Elements none

Value the number of columns

Tag **<active_area>** min=0, max=1

Description A shape file which selectively activates part of the domain.

Attributes none

Elements none

Value a SHP file reference

Tag **<rotation>** min=0, max=1

Description An angle to rotate the domain by in an anti-clockwise direction.

Attributes none

Elements none

Value an angle (in degrees)

Tag **<topography>** min=1, max=Inf

Description The topography tag can be used to read in ASCII grids or shape files to define topographical features. Please note the order in which the topography files are listed in these tags in 2D solver control XML file is important as during the 2D solver simulation the topography files are read from the tag on the top to the tag on the bottom in the tags mentioned in 2D solver control XML file and the topography file from the tag on the bottom of the XML file will take precedence over the one mentioned higher on the list in the area it is applied to.

Attributes none

Elements none

Value A shape or ASCII grid file reference

Tag **<time>** min=1, max=1

Description The time tag encloses tags which describe when the simulation should start and how long it should run for.

Attributes none

Elements <start_time> min=0, max=1

<start_date> min=0, max=1

<total> min=1, max=1

Value none

Tag **<start_time>** min=0, max=1

Description Determines the start time of the simulation, if no start time is specified, a start time of 00:00 will be assumed

Attributes none

Elements none

Value a time in the format hh:mm:ss

Tag **<start_date>** min=0, max=1

Description Determines the start date of the simulation, if no start date is specified, a start date of January 1st 2000 will be assumed

Attributes none

Elements none

Value a date in the format yyyy-mm-dd

Tag **<total>** min=1, max=1

Description The total amount of time to run the simulation for. The units of time must also be specified in the units attribute

Attributes unit (man) the units used to describe the run time information, either second, minute, hour or day

Elements none

Value the total number of time units to run the simulation for

Tag **<run_data>** min=1, max=1

Description The run_data tag encloses a series of tags describing how the model should be simulated, such as the time step to use, numerical scheme etc.

Attributes none

Elements <time_step> min=1, max=1

<scheme> min=1, max=1

<beta> min=0, max=1

<eddyviscosity> min=0, max=1

<wall> min=0, max=1

<upwind> min=0, max=1

<flddry> min=0, max=1

<nadvit> min=0, max=1

<drydepth> min=0, max=1

<fricdepth> min=0, max=1

Value none

Tag **<time_step>** min=1, max=1

Description Specifies the 2D time step to use for this domain

Attributes none

Elements none

Value a time step in seconds

Tag **<scheme>** min=1, max=1

Description Specifies the numerical scheme to use.

Attributes none

Elements none

Value either ADI or TVD

Tag **<beta>** min=0, max=1

Description Weighting factor for the advection term in the shallow water equations.

Attributes none

Elements none

Value 0 - Inf (default 1)

Tag **<eddyviscosity>** min=0, max=1

Description Kinematic eddy viscosity parameterising horizontal turbulent momentum transfer.

Attributes none

Elements none

Value 0 - Inf (default 0)

Tag **<wall>** min=0, max=1

Description Specifies the boundary conditions at a wall, as either slip or no slip, corresponding to a smooth or rough wall.

Attributes none

Elements none

Value either slip or noslip (default slip)

Tag **<upwind>** min=0, max=1

Description Specifies whether the scheme uses and upwind finite difference in the calculation of the advection term (on), or a centred difference (off)

Attributes none

Elements none

Value Either on or off (default on)

Tag **<flddry>** min=0, max=1

Description Specifies whether the scheme uses the new or the old wetting and drying algorithm (old version included for backwards compatibility).

Attributes none

Elements none

Value Either old or new (default new)

Tag **<nadvit>** min=0, max=1

Description Number of sub-iteration per time step

Attributes none

Elements none

Value 1 - Inf (default 2)

Tag **<drydepth>** min=0, max=1

Description Depth in metres below which cells are considered dry

Attributes none

Elements none

Value 0 - Inf (default 0.01)

Tag **<fricdepth>** min=0, max=1

Description Depth below which the implicit friction scheme is used to aid stability

Attributes none

Elements none

Value 0 - Inf (default 100.0)

Tag **<calcdepth>** min=0, max=1

Description Depth below which the modified depth calculation scheme is used

Attributes none

Elements none

Value 0 - Inf (default 0.5)

Tag **<initial_conditions>** min=0, max=1

Description The initial conditions tag is used to either set global initial conditions or initial conditions in specific areas.

Attributes type (man) the type of initial condition being specified, either globalwaterlevel, globaldepth, elevationfile or depthfile

Elements none

Value depending on the type attribute, either the depth or elevation in metres, or the file name of an elevation or depth file

Tag **<roughness>** min=0, max=1

Description The roughness tag is used to either assign a global roughness coefficient, or to read roughness values from a file.

Attributes law (man) the roughness law being used, either mannings or chezy

Type (man) the method we will be using to read in roughness - either global or file

Elements none

Value Either a file name if type file has been specified, or a coefficient value if a global type has been specified

Tag **<boundary_conditions>** min=0, max=1

Description The boundary_conditions tag encloses all boundary tags used in the current domain

Attributes none

Elements <boundary> min=1, max=Inf

Value none

Tag **<boundary>** min=1, max=Inf

Description each boundary tag contains information to specify a boundary condition type, location and series of values

Attributes none

Elements <BC> min=1, max=1

<file> min=0, max=1

<xy> min=0, max=1

<value> min=1, max=1

Value none

Tag **<BC>** min=1, max=1

Description The BC tag describes the type of hydraulic boundary

Attributes none

Elements none

Value totalflow, flowperunitwidth, verticalflow, verticalflowperunitwidth or elevation

Tag **<file>** min=0, max=1

Description The file tag contains a reference to a shape file describing where the boundary should be applied

Attributes none

Elements none

Value a file name

Tag **<xy>** min=0, max=1

Description The XY tag can be used instead of the file tag to specify a series of X,Y coordinates. 2D solver will join the points and apply the boundary condition over the resulting line.

Attributes none

Elements none

Value A space separated list of X,Y coordinate pairs, one par per line.

Tag **<value>** min=1, max=1

Description The value tag contains the actual boundary data, for example time and flow values in a QT boundary

Attributes type (man) time_var, fixed_vaue or IED

time_units (op) the time units of any included time series, second, minute, hour or day

Elements none

Value If the type has been specified as time_var, a list of white-space separated value pairs, one pair per line, if the type has been specified as fixed var, the value of the variable which will remain fixed through time, if IED has been specified, a reference to the IED file.

Tag **<hydrology>** min=0, max=1

Description The hydrology tag contains information describing hydrological sources

Attributes none

Elements <source> min=1, max=Inf

Value none

Tag **<source>** min=1, max=Inf

Description Each source tag contains tags referencing a polygon and a data series

Attributes none

Elements <file> min=1, max=1

<value> min=1, max=1

Value none

Tag **<file>** min=1, max=Inf

Description The file tag references the shape file containng polygons describing where rainfall should be applied

Attributes none

Elements none

Value a file name

Tag **<value>** min=1, max=Inf

Description The value tag contains a time series of rainfall data

Attributes timeunits (man) the units used in the time series, second, minute, hour or day

units (op) the units of the rainfall data, mm/hr, mm/h, m/s or in/hr

Elements none

Value a time series

Tag **<output_results>** min=1, max=1

Description The output_results tag contains a series of output tags

Attributes none

Elements <output> min=1, max=Inf

<massfile> min=0, max=1

<check> min=0, max=1

Value none

Tag **<output>** min=1, max=Inf

Description The output tag contains details of the types of variables to capture, how to write them and how often.

Attributes expand (op[A7] ) Expand the water level surface into dry areas by this number of cells.for improved high resolution flood mapping.

output_id (op) used to specify an output file name

format (man) specifies the output format, either SMS9 or CSV format

Elements variables min=1, max=1

frequency min=1, max=1

xy min=0, max=1

Value none

Tag **<variables>** min=1, max=1

Description Specifies the variables to output from the simulation

Attributes none

Elements none

Value Either Elevation, Flow, Velocity, Depth or Bedelevation

Tag **<frequency>** min=1, max=1

Description The frequency at which to write results

Attributes none

Elements none

Value A frequency (in seconds)

Tag **<xy>** min=0, max=1

Description A list of X,Y coordinates at which point information will be extracted and written to a CSV file

Attributes none

Elements none

Value A space seperated sequence of X,Y pairs, one pair per line.

Tag **<massfile>** min=0, max=1

Description The name and location of the mass balance file to be written.

Attributes frequency (op) the frequency at which information will be written to the file (seconds)

Elements none

Value A mass balance file location

Tag **<check>** min=0, max=1

Description The name and location of the check files to be written.

Attributes none

Elements none

Value A check file location