Flood Risk Intelligence
November 22, 2021

Fathom-Japan launch FAQ

Today Fathom has launched its latest flood hazard data and maps for Japan, Fathom-Japan. The model which simulates fluvial, pluvial and coastal risk at 10-meter resolution will provide users with the ability to identify and assess flood risk across the country; as well as enhance their understanding of how this will evolve under an increasingly uncertain climactic landscape.

Developed as a result of Fathom’s partnership with the resilience-as-a-service provider One Concern, Fathom-Japan utilises the most sophisticated datasets currently available. This includes technology that has been built in-house, as well as by partners such as Prof. Yamazaki’s Flow Direction Map developed out of the University of Tokyo’s Global Hydrology Group.

Before accounting for flood defences, Japan’s population has one of the highest exposures to flood inundation in the event of a 1-in-100 year flood. However, the presence of flood defences such as levees has helped to build-in resilience and reduce the exposure of the population to these flood events. Tools like Fathom-Japan, enable those looking to pinpoint flood exposure to integrate climate-adjusted national flood risk into the planning process and proactively manage future risk with greater confidence.

Obhiro 1 in 100 year defended fluvial flood event, under a 2020 climate scenario.

FAQs

What are the key features underpinning this model?

When building a model in Japan, it is essential to consider the region’s atypical topography. With rugged and mountainous terrain, densely populated urban cities and a complex channel network, ensuring that we could accurately pinpoint high-risk areas and represent them realistically within the model were essential.

Coupling localised LIDAR data with our dynamic channel solver meant that we could estimate channel geometries for the entire country. 

For our fluvial model, we estimate river channel defences using global defence and urbanisation datasets. For our coastal model, we apply our levee detection algorithm to identify defences within the high-resolution terrain data. From this, our team were then able to account for the influence that Japan’s defences have on decreasing exposure. 

Another key feature is that our team have married historical records with outputs taken from the D4PDF future climate model ensemble. The outcome is a model that can provide actionable insights not only for the present day but also under 2035 and 2050 future climate scenarios.

Who will benefit from this data?

With a highly specialised market, Fathom-Japan offers a unique advantage to decision-makers, infrastructure specialists and portfolio managers looking to future proof assets and investments within the region.

The model, which can be offered as a national dataset or cut into specific regional shapefiles, will enable global entities and local firms to identify, model, and build resilience to increasingly frequent and severe climate threats.

Where can I access this model?

We work closely with our customers to outline their specific geographical needs. Once this has been done, Fathom provides the raw shapefiles in a GeoTIFF format. Users can then load this data through any GIS software. 

How can I view the Japan flood maps? 

Our specialist team are able to offer free sample data for a number of selected cities across Japan. Get in touch with our team to find out more. 

Learn more about Fathom-Japan here.

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