Why use 1D river modelling?
  • 13 Sep 2022
  • 2 Minutes to read
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Why use 1D river modelling?

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1D modelling is most effective in channels or pipes and so river systems and urban drainage systems are often modelled in 1D. In 1D river modelling, nodes specify the underlying riverbed geometry and roughness, plus other features such as structures (bridges, culverts, etc.).

To run a 1D only simulation (for example, if modelling a river network in 1D) the user provides details such as the flow entering the river (e.g. from a design storm) and a timestep. Based on this information and the specified initial water level in the river, the software calculates the new water level (stage) and flow, at all the nodes, at each requested timestep.

What is needed to run a 1D river simulation?

A 1D simulation always requires a network to represent the 1D components. If modelling a river, a 1D river network describes the river itself.

A river network consists of multiple 1D units, or nodes, to provide the physical properties of the river – geometry and roughness of the river bed in river sections, details of boundaries to describe how water enters and leaves the system, and, if present within the modelled reach, details of other structures and features (bridges, culverts, reservoirs, etc.). 

Initial conditions are also required for a 1D simulation. These provide the initial water level throughout the network. If these are not defined realistically the model may become unstable and fail.

When setting up a 1D river simulation, details of your river network and initial conditions must be provided, alongside timing and run options (whether the simulation is steady-state or unsteady). 1D river simulations can be run individually or in batches.

Multiple parameters can be calculated in a 1D river simulation; flow, stage, velocity, total energy, channel conveyance and average shear stress, among others.

What can I visualise from a 1D river simulation?

Flood Modeller’s graphical interface provides the ideal platform for visualising all aspects of your model, both throughout the build process, and for result analysis and processing. Prior to running a simulation, the map view allows visualisation of all modelling components, together with background mapping. For 1D networks, this consists of unique icons identifying each node of the river or pipe system itself, together with links showing the connectivity of the network.

Each node then has further visualisation options; for river nodes, buttons are provided to create ‘Cross Section’ and ‘Long Section’ plots from your river data, and inflows can be viewed in tabular or graphical form, for example.

The results from a 1D river simulation can be viewed in ‘Time Series’ plots, showing changes in the water level over time at a specified node. ‘Cross Section’ plots (showing a cross-sectional “slice” of the river) and ‘Long Section’ plots (showing the water level along the river from upstream to downstream) can both be animated to see the water level change over time. Tools are also provided in the interface to post-process model outputs to generate data such as flood maps and animated maps.

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