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Hawker, L.,
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Kirkpatrick, T.,
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Lord, R.,
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Groeger, A.,
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Thuy, T.,
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Fox, S.,
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Agyemang, F.,
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Nam, P.
Research led by Laurence Hawker and co-authored by Fathomers Jeff Neal and James Savage has integrated Fathom’s terrain data into a global flood model to calculate flood exposure in data-scarce Vietnam
Flooding is the world’s most frequent and costly natural hazard. Its impacts are felt most severely in developing countries, and Vietnam is one of the most flood-prone countries in the world because of its long coastline, densely built-up urban areas and the fact that many of its industrial assets are located in floodplains.
The population exposed to flooding in Vietnam is already high (38 %) and growing. That’s why understanding the country’s flood risk, as well as the socio-economic factors that can exacerbate or alleviate flooding’s impact, is crucial.
However, Vietnam is in a data-scarce region, and the quality of the flood hazard maps that do exist is extremely varied. Global hydrodynamic flood models have been developed to fill this gap, but to provide high-quality flood simulations, modelers need to use a digital terrain model that has vegetation and buildings removed.
In this new research, the team developed and evaluated a next-generation global flood model based on FABDEM, the latest “bare earth” global terrain dataset from Fathom and the University of Bristol, and used it to estimate flood exposure in Vietnam.
It was the first time FABDEM’s use in a global hydrodynamic flood model had been assessed, and the first time the data had been applied in Vietnam.
Learn more about FABDEM+, Fathom’s bare-earth elevation data for every location in the world.
The objective: Filling the research gap in Vietnam
As a study area, the researchers chose the Central Highlands of Vietnam and its surrounding provinces, a region frequently affected by pluvial, fluvial and coastal flooding and with some of the highest levels of poverty in the country.
The aims of the research were:
- To integrate FABDEM data into Fathom’s existing existing global flood modeling framework and simulate hydrodynamic models using LISFLOOD-FP
- To compare the FABDEM-based model with previous versions based on MERIT DEM
- To validate the model using two data sources: remote sensing data from the Sentinel-1 satellite, and on-the-ground observations taken from a survey of almost 1,000 households conducted by the researchers in 2019
- Use both models to calculate the hazard and population exposure in the region.
The results: Bare earth simulation reveals higher exposure
The research yielded these key findings:
- Thanks to better grid spacing and the removal of both buildings and trees, the model built using FABDEM gave a more realistic picture of flooding extents than the model built using MERIT DEM.
- The agreement between the FABDEM model and the remote sensing data was greater than the agreement between the two validation data sets.
- The researchers presented flood exposure estimates and hazard information for the study area in Vietnam. The FABDEM model gave consistently higher estimates than the MERIT model across all return periods. Notably, the FABDEM model found a greater proportion of flood exposure in urban areas.
- The proportion of people exposed to flooding in each province is significant, with almost a third of the total population of Ninh Thuan and Quang Ngai exposed to the 1-in-100-year event.
This research helped address the lack of studies of the Central Highlands of Vietnam and highlighted the high level of exposure to flood – especially in urban areas. With extreme events expected to become more common and with increasing urbanization, the need for proper planning to minimize the impacts of flood risk in the region is becoming more urgent.
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