Broad scale modelling

Broad scale models are developed relatively quickly and inexpensively to provide a baseline understanding of flood risk from different sources (e.g. rivers, the sea, intense rainfall, groundwater and reservoir impoundment failure) across wide areas.

Such models are built from datasets with complete coverage across the area of interest using a generalised methodology and simplifying assumptions where necessary – for example, where a certain aspect of the physical system cannot be modelled efficiently or explicitly at that scale.

The outputs from these models have proved extremely useful to local and national governments and flood risk management authorities, as means of planning FRM investment, and developing an objective basis for prioritising more detailed, local investigations in flood risk ‘hotspots’. Where resources permit, we have also developed web-based solutions for improving the models where better local data exists and reviewing draft flood mapping prior to publication.

International work

Global flood risk is expected to increase due to climate change and development in areas at risk.

Actions can be taken to manage these risks and reduce the impacts on our physical and naturally built environment. To inform these actions and allow investment in risk management to be prioritised effectively, the availability of accurate, timely and scalable flood mapping is essential.

Generating efficient flood models requires the use of cutting edge technology and analytical techniques to produce and analyse petabytes of data.


Our flood risk modelling system, JFlow® was developed in 2002. JFlow® provides a unique capability to model flood risk at a large scale without compromising on the detail needed to provide accurate mapping at a local level. Since then we have continued to invest in its development and expand
its capabilities.

The software has been applied to many regional, national, continental and global flood inundation projects. Run on the world’s largest dedicated flood modelling computer grid, JFlow® allows large-scale flood and hazard mapping in unparalleled timeframes.

Project case studies

JBA Global Flood Maps broad scale modelling project example

Global Flood Map – JBA licensed product

Our Global Flood Map (GFM) was developed using our in-house flood inundation model, JFlow®, and is licensed by many of the major insurers, reinsurers, brokers, cat modelling companies and governments across the UK
and internationally.

The GFM offers consistent fluvial and pluvial flood mapping of the whole world (covering 168 countries) and can be licensed as a whole or on a per-country basis.

It brings together all of the necessary elements to produce a credible indicative flood map which is consistent in terms of input data, modelling approach, coverage and resolution.

JBA Flanders Pluvial Flood Map

Flanders Pluvial Flood Mapping

Vlaamse Milieumaatschappij (VMM) asked us to develop and refine a methodology for high-resolution pluvial flood mapping suitable for implementation across Flanders. This specification was tested for two pilot areas and the results for the T10, T100 and T1000 design events compared against local knowledge and observations from previous pluvial flood events.

Delivered with our JFlow® software using a range of processes, developed from experience gained on the Environment Agency’s Updated Flood Map for Surface Water, we ensured an efficient project in respect of cost and programme to be delivered.

JBA Thames Water PR19 Flood Resilience Modelling

Flood hazard data

To better assess and understand the flood resilience of thousands of assets in preparation for their next business plan in 2019, Thames Water appointed us to prepare a suite of fluvial and pluvial flood depth, velocity, hazard and water level mapping for their entire service region totalling 14,600 km2. Our JFlow® hydraulic modelling software was selected over use of freely available flood outlines from the national
Environment Agency.

We prepared 2m resolution two-dimensional (2D) pluvial hydraulic models of the entire region. Direct rainfall was applied as composite time-intensity for return periods ranging from 10 to 1,000-years, adjusted to take account of natural infiltration processes and man-made drainage infrastructure where appropriate. In addition, two storm durations; 1 and 10 hours were simulated, with the results formed by merging the depth/hazard grids of each duration. 2D fluvial modelling was also carried out at a 5m resolution for all watercourses in the region for a wide range of return periods and climate change scenarios.

JBA SEPA pluvial flood hazard dataset

Pluvial Flood Hazard Dataset

We produced regional flood maps for the Scottish Environment Protection Agency (SEPA) building upon a number of previous studies by other contractors. The aim of the regional study was to provide data of increased resolution in selected areas, covering 73 catchments, as defined by SEPA. The modelling covered an area of approximately 22,000 km2 and was undertaken using JFlow®, our two-dimensional (2D) fully hydrodynamic
modelling software.

The work was driven by  legislation in the form of The Flood Risk Management (Scotland) Act 2009 and European Commission Directive 2007/60/EC. DTM’s were created using LIDAR where available and NEXTMap were not. 14 rainfall scenarios were modelled and varying data sets delivered to the client.

We can help you

If you would like to discuss how we can work together please contact Neil Hunter.
+44 (0)1756 699500