Southwest Environmental Limited

Flood Zone Modelling

A model is a mathematical way of try to mimic real life events, or sometimes future events. With Flood Zone Modelling we try to predict which areas of land will flood given a set of climatic events. We then end up with a set of risk values (1 in 10 year) for example and we can create areas (zones) on a map for each risk level.

Flood Zone Modelling . . . . in a Nutshell

Described simply in a flood zone modeling exercise we mix land and weather mathematically and try to present the results clearly. 

Inland areas are the simplest to describe as they are not influenced by tides and storm surge, which complicate costal modeling runs.

Considering our simplified area, we "dump" a certain amount of rain on a given land area. The land is not perfectly flat and so certain bits "fill up" more quickly and more deeply than others, and in this way we can start to produce a flood risk zone map.

What Base Maps do you Use for Flood Zone Modelling?

The overly the right shows flood zones overlain on to satellite imagery. This is useful in countries where there is poor map coverage, but in the UK we would typically use ordnance survey mapping.

Why do I need Flood Zone Modelling?

Bespoke flood modeling has become very common in the UK, as most the the flood data available from commercial and government sources does not account for climate change, and as such may be inaccurate.

How Does Flood Zone Modelling Work?

The image to the left shows how the model use points to create a cloud of data point within a model. The layers is carried out at various points, and the results combined to create surfaces.

Do You Need a Powerful Computer?

To run a model over a very large area requires a powerful computer, however recently you can rent space on a ready made computer which helps with costs if we have to undertake large modeling exercise, Amazon Web Services is one such service provider, although in the winter we like to try and run the model in the office to make use of the waste heat from the computer processors which is considerable!

What can be Modelled?

Using the model we can also create exceedance flow routes, water velocity, hazard, depth and all manner of mapping.

As previously mentioned flood zone modeling is complicated in coastal regions as we have to account for tidal and storm surge influences within the model.

The Cost of Bespoke Flood Zone Modeling

The cost of bespoke flood zone modeling starts at around £2000 + VAT and this would rely on to reuse of pre-existing flood data which we use to populate the model and then re-run to add in climate change allowances.