Time-varying boundary conditions file (.bdy)

This file is needed when selecting QVAR or HVAR in the .bci file. In this case, a time series (also known as hydrograph) needs to be loaded at either a boundary segment (an edge) or a point source (in pre-specified cells located inside the computational domain). The time series is either free-surface elevation or unit-width discharge data, aimed to specify the time varying-boundary conditions.

The .bdy file is used to specify such a time-varying boundary condition and has the following format:

• Line 1. Comment line, ignored by LISFLOOD-FP

• Line 2. Boundary time series name (this should be consistent with notation used in the .bci file)

• Line 3. Number of time points at which boundary information is given followed by a keyword for the time units used (either days, hours or seconds)

• Line 4. Value1 Time1

• Line 5. Value2 Time2

• …

• Line n. Valuei Timei

Note that Valuei is the value of the relevant quantity for the given boundary type. That is, for HVAR boundary types, Valuei is a free-surface elevation in metres; whereas, for QVAR boundary types, Valuei is given as unit-width discharge with units of square metre per second.

In case studies “3. Valley flooding following a dam failure” or “4. Carlisle 2005 urban flooding”, examples are provided on how to set up .bdy file to specify time varying-boundary conditions

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