Building on an extensive history of river gauges, flood defences and climate risk information.

Fathom-Japan offers a next-generation approach to simulating flood risk in Japan.

Containing a rich body of streamflow and rainfall historical records, when combined with the latest climate data, Fathom-Japan provides a comprehensive assessment of evolving risk across three flood perils.
return periods
From 1:5 year to 1:1000 year.
Return periods can be categorised to suit your risk appetite.
pluvial &
Assess the impact of
multiple flood types.
Updated 2020,
2035 and 2050
climate states.
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Flood defences explicitly
built-in using new levee
detection algorithms and localised terrain data.
of river
Japan possesses one of the most complex river infrastructures in the world, both by natural development and human design.
Our flood hazard data represents every river channel in Japan, regardless of size and complexity.
This is achieved by coupling detailed river network maps based on localised LIDAR data with Fathom's market leading dynamic channel solver.

Combining data in this way allows us to define channels in a much more accurate and realistic way, whilst also drawing upon over ~30,000 years of historical water level records.
Fathom-Japan's future climate scenarios are underpinned by data from the D4PDF ensemble of climate models.

By incorporating data from climate models,
Fathom-Japan's users can access a broad range of actionable data sets around flood risk that will support them to identify, model and build resilience against increasingly frequent and severe climate threats.

Fathom-Japan simulates flood events at 2020, 2035 and 2050 for 10 return periods
This varies from high frequency to low frequency flood events
Tokyo 1000 year fluvial flood event (undefended)
Fathom-Japan simulates flood events at 2020, 2035 and 2050 for 10 return periods
This varies from high frequency to low frequency flood events
Tokyo 5 year fluvial flood event
Fathom-Japan benefits from an impressive portfolio of award winning research and methodologies spanning two decades.
In a recent paper published in Water Resources Research, Professor Bates assessed the methodologies underpinning Fathom-US.

He found significant improvement across the model’s ability to simulate regular coastal area activity and high-frequency events.

A similar modelling approach has been applied to Fathom-Japan, with a paper validating its methods currently in production.

Secondly, Fathom has worked alongside academic partners to ensure the richness of research and data within Fathom-Japan. This includes the use of data from the Global Hydrodynamics Lab, which is part of the U-Tokyo Global Hydrology Group in the Institute of Industrial Science at the University of Tokyo.

This is part of a long-standing relationship that Fathom has with researchers from the University of Tokyo, with whom they have co-authored numerous hydrological papers. You can access this research here.
Finally, Fathom has validated this model against 6 observed events provided by our partner One Concern and spatial extents of flooding produced by the Geospatial Information Authority of Japan (see below).

Whilst there are limitations in aerial photography, our team found that Fathom-Japan's flood events corresponded well with the GSI's observations.
Fathom have modelled our flood hazard data for Japan against aerial imagery produced by the Geospatial
Information Authority of Japan (GSI).

Observed event 1: Kinugawa River, 2015
Comparison in the quality of Global 2.0 and Global 1.0. We work hard to constantly improve our data.
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Fathom-US provides the complete picture of US flood exposure.
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Fathom-UK CAT accurately calculates loss and exposure on a national scale.


The first fully peer-reviewed and validated US flood catastrophe model.
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// Fathom delivered high-quality analyses to improve the global flood hazard classification in ThinkHazard! and helped make the data available for disaster risk management activities in developing countries.//
Dr Brenden Jongman
Disaster Risk Management Specialist,