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Key facts

  • Modelling surface and sub-surface flows within a heavily urbanised catchment.

  • Flooding mechanisms involving overland flow and manhole surcharge.

  • Simulations run in Flood Modeller were up to 49% faster than alternative software.

  • The model was numerically stable throughout the simulation.

  • Flood Modeller’s GIS interface, toolbox, and pre and post-processing capabilities removed the need for third-party software.

Feature focus

1D Urban solver

The 1D urban solver allows users to combine surface and subsurface flow to obtain a detailed and integrated understanding of flood risk in urban areas, directly within Flood Modeller’s powerful user interface. It enables users to develop integrated catchment and systembased solutions within a single software solution.

For more information:

Flood Modeller was used to understand the flooding mechanisms involving overland flow from an open channel and the subsequent overflowing of the sewer system in a small and heavily urbanised catchment.

The steep and heavily urbanised catchment in West Yorkshire, England, ranges from 30 to 91mAOD in elevation and covers 0.9km². A small ordinary watercourse flows easterly through the area of interest. The majority of its 940m reach is culverted with the exception of a short section of open channel before re-entering a culvert prior to its confluence with another watercourse.

With the frequency and severity of floods increasing along with the rapid growth of urban development, there is more pressure to protect urban areas from flooding and to preserve water quality.

Historically, due to cost, time and data requirements, flood modelling only took into consideration the impact from river systems which led to the misrepresentation of flood risk as it didn’t assess the interdependence of surface and subsurface flows. An integrated catchment management approach is the best way to planning and designing more sustainable solutions to prevent flood risk.

Overland flow from Flanshaw Beck and from the surcharge of manholes have caused surface flooding in a number of properties within the catchment. It was therefore necessary to better understand the flooding mechanisms affecting properties and roads in this small but heavily urbanised area.

Flood Modeller offers an easy to use, fast and cost-effective solution for fully integrated catchment modelling, using Flood Modeller’s 1D river solver to model channels, its 2D solver to model overland flow across floodplains and the 1D urban solver to model sewer networks.

In this study, Flood Modeller’s 1D urban solver was dynamically linked to its 2D solver due to the speed, stability and accuracy of the software. Its intuitive GIS-like interface provided a wide-range of model building tools, as well as pre and post-processing capabilities, removing the need for third-party GIS software.

Tools such as the Damage Calculator helped quickly assess the overall economic impact of the flooding, providing a better understanding of the severity of a flood event and calculating the damage for each property affected.

Prior to the modelling, an initial test phase was undertaken to determine the most appropriate software for this project. It found that Flood Modeller enabled each simulation to run up to 49% faster compared to other available software. The results were not sensitive to the timestep selection, and were in close comparison and reflected, to a high level of acceptability, the flood mechanisms at study location. The model was also numerically stable throughout the simulation.

The 1D urban solver proved to be an extremely powerful solution for evaluating the impact of extreme storm events on sewer systems, particularly when linked to the 2D solver to model the resulting surface flows and possible flood scenarios for the area of interest.

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