1D River Solvers

Simulate flows and levels in open channels, floodplains, reservoirs and estuaries

Developed for over 40 years, Flood Modeller’s advanced 1D solvers have become some of the fastest and most robust solutions available. It makes them an ideal choice for a wide-range of engineering and environmental applications. The solvers have been subjected to extensive testing and benchmarking against observations, analytical solutions and other modelling software.

Suited to modelling flows and levels in open channels, floodplains, reservoirs and estuaries

Trusted by users for being fast, reliable and providing robust solutions

Key facts

Includes a comprehensive range of structures including gates, abstractions, weirs and pumps

Allows logical rules to be applied to the operation of different structures

Ability to apply point and distributed boundary inflows/conditions

Extensively and independently tested and benchmarked by government agencies and academics

Relied upon by government agencies for flood forecasting

At the core of Flood Modeller are its industry-leading steady and unsteady 1D solvers. They are suited to subcritical, supercritical and transitional flow regimes to confidently apply them to applications, ranging from steep river flows to tidally influenced estuaries.

 

In addition to the full hydrodynamic solvers, Flood Modeller includes flood routing capabilities, including the Muskingum and Muskingum-Cunge methods, providing users with a simplified way to calculate downstream discharges.


The 1D solver provides a comprehensive range of hydraulic structures, including gates, abstractions, weirs and pumps. Structures can be operated using logical rules for applications such as controlling the gate opening of a sluice or turning a pump on or off. This gives Flood Modeller a much wider range of application when compared to other 1D modelling software.

Flow boundaries to the 1D river solver can be applied either as a point inflow/outflow or distributed inflow/outflow along a river reach using one of the hydrological boundary units or the flow time boundary unit. Water level boundaries can be defined using either a time series water level boundary unit or as an automatically generated flow-head relationship using the normal/critical depth boundary unit. Boundaries to the 1D river solver can also be from links to the 2D solver and the 1D urban solver. 

1D model results can be effectively interrogated through long-section and cross-section graphs, which can be animated to show changes in water levels throughout your model runs.

Steady-state solver

The steady state solver provides both, direct steady-state and Pseudo-Timestepping, methods to optimise run-time and enhance model stability. It is most often used to obtain an estimate of the initial conditions for your model. 

In order to carry out unsteady simulations, an estimate of the initial conditions (flow and stage) are required at every model node. This is most often obtained by carrying out a steady state simulation at the proposed start time.

 

The main steady state solution is the Direct Method and is applicable to in-bank flow regimes. It is a fast and very accurate solution which requires very little initial data. It also incorporates an optional accurate supercritical and transcritical flow solver which has the capability of modelling hydraulic jumps and supercritical flow to a high degree of accuracy.

The Pseudo-Timestepping method uses a Preissmann 4-point scheme and is often used to develop initial conditions for unsteady runs or where flows are initially out of bank. These initial conditions are used for the steady state run, with the boundary conditions held constant for the time at which the solution is required. The model is run until all the irregularities and inaccuracies in the guessed initial conditions have propagated or been dissipated out of the system.

Unsteady-state solver

The unsteady state solver uses the Preissmann implicit scheme to solve the equations for free surface flow, based on the Saint-Venant equations for flow in open channels. The solver provides various features which have been specifically designed to improve model performance and management capabilities.

The unsteady state solver uses the so-called “box” finite difference operator whose use was reported by Preissmann (1960). This operator is implicit, which means that long time steps can be used in simulating, for instance, regional flood events. These operators enable the differential equations describing channel flows to be transformed into a set of linear algebraic equations connecting the flows and depths at discrete locations or nodes along the channel.

 

The Preissmann implicit scheme solve the equations for free surface flow, based on the Saint-Venant equations for flow in open channels. These are used in conjunction with the governing hydraulic equations for each hydraulic structure.

 

These equations are inevitably a combination of empirical and theoretical equations, many of them non-linear. The non-linear equations are first linearised and the solution to the linear form of the problem is then found.

 

The solver provides various features which have been specifically designed to improve model performance and management capabilities, during an unsteady simulation.

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