How JBA’s new Inland Flood Model tackles longstanding challenges?
Flooding remains one of the most widespread and costly natural hazards in the United States, putting millions of properties at risk each year. Managing this exposure requires a deeper, more detailed understanding of where and how flooding occurs – something traditional tools have struggled to deliver. JBA’s new US Inland Flood Model was developed to meet this need, providing high-resolution, science-based insights that strengthen resilience and support more effective insurance solutions. Here, Owen Hinks and Dr David Cross, catastrophe model specialists at JBA Risk Management, explain how the model brings a new level of clarity to understanding flood risk nationwide.
Drawing on its new high-resolution US Inland Flood Model, JBA estimates that one in three properties in the United States are at risk of inland flooding. Understanding and managing this risk demands high-resolution data that credibly captures the complexities of flood dynamics. In a flood insurance landscape largely shaped by the National Flood Insurance Program (NFIP), private (re)insurers face unique challenges. To expand coverage, diversify products, and complement federal efforts, they need reliable, detailed hazard data and robust probabilistic models.
JBA’s new US Inland Flood Model meets this need head-on. Purpose-built to support the expanding private flood insurance market, the model delivers high-resolution, comprehensive, and transparent flood hazard data. By equipping (re)insurers, policymakers, and communities with the insights they need, the model empowers smarter decision-making – ultimately strengthening resilience and reducing the financial impact of flooding.
A key part of developing JBA’s US Inland Flood Model was a close collaboration with Applied Research Associates (ARA), a leading US hurricane modelling company. By aligning JBA’s flood science with ARA’s HurLoss® model for hurricane wind and storm surge, the two companies have created a coherent framework that allows for a more connected understanding of hurricane-related perils. This collaboration gives clients the flexibility to assess wind, surge, and inland flood risk together or independently, helping (re)insurers gain a clearer view of potential losses and build more resilient portfolios.
The evolution of the US flood insurance market
Since its inception in the late 1960s, the NFIP has provided the vast majority of flood insurance coverage in the US, addressing what was once considered an “uninsurable” peril. The program has made significant strides in offering affordable flood protection nationally. However, its rigid legal framework and reliance on outdated data have resulted in coverage gaps that leave many communities and businesses underserved.
Advances in flood risk science and catastrophe modelling have now opened the door to private sector participation. Regulatory changes in 2016 allowed property owners to seek private flood coverage in FEMA-designated high-risk zones, leading to increased private market involvement.
Yet, barriers remain. Decades of NFIP dominance have suppressed consumer demand for private insurance, while limited access to independent, high-quality flood analytics has kept many insurers on the sidelines.
Criticisms of the NFIP's data quality – particularly its flood maps – have been well documented in recent analyses by Lloyd’s and Insurify, highlighting the pressing need for more precise and comprehensive tools. For new products to gain traction, they must exceed current standards in credibility, transparency, and usability.
Meeting market needs: JBA’s Inland Flood Model
To compete in the US flood insurance market, private (re)insurers need models they can trust. JBA, a global leader in flood risk management, delivers exactly that. Our US Inland Flood Model is purpose-built for the private sector, offering high-resolution, property-level analytics that integrate seamlessly with existing risk modelling platforms.
Nationwide, Consistent coverage
The model provides full coverage across the contiguous US, built on a consistent hydrological and hydraulic modelling framework. This allows insurers to evaluate risk uniformly across portfolios – regardless of regional flood drivers.
Dual flood type modelling
Both fluvial (river) and pluvial (surface water) flood types are modelled using time-series-based hydrological simulations and 2D hydraulic modelling, ensuring spatial coherence and realistic catchment response.
Highest-resolution mapping
JBA’s 5-metre resolution flood maps – embedded within the model – represent the highest-resolution inland flood hazard data commercially available in the US Incorporating best-available terrain data, including USGS LiDAR, the maps strip out features such as levees and bridges to robustly simulate natural flow paths. This level of detail allows insurers to distinguish between shallow and deep flooding, evaluate risk beyond FEMA’s Special Flood Hazard Areas (SFHAs), and tailor policies to the characteristics of individual properties.
Probabilistic event modelling
The model includes a stochastic catalogue of more than 376,000 unique flood events, simulating 500,000 years of flood activity. Crucially, these are correlated with ARA’s HurLoss® catastrophe model for wind and surge, allowing exploration of compound events from hurricanes and inland flooding. This supports full probabilistic modelling for use in pricing, accumulation management, and stress testing.
A scientific, independent perspective
Importantly, the model is developed independently of FEMA zone boundaries, producing flood extents that differ from FEMA’s maps, illustrated in the Texas example in Figure 1. By presenting a purely scientific view of flood hazard – derived from observed and synthetic rainfall, hydrology, and terrain data – the model allows private insurers to build products in areas not currently mapped by FEMA, apply risk-based pricing beyond regulatory constraints, and provide investors and clients with transparent, defensible insights into flood risk.
Inland flood risk insights from the model
Understanding inland flood risk in the US
According to analysis of the NFIP Community Status book version 1, the NFIP covers over 90% of US communities, but participation is voluntary. Properties in non-participating jurisdictions remain unprotected, and even within mapped areas, coverage limitations persist.
FEMA’s SFHAs primarily focus on fluvial and coastal flooding, with limited treatment of pluvial events. JBA’s model, in contrast, explicitly simulates pluvial flooding at all return periods, offering a much fuller picture of flood risk across the US.
Quantifying risk nationwide
FEMA’s US structures dataset indicates that there are 130 million buildings over 450 square feet in the contiguous US JBA’s model finds that 38.6 million of these – nearly 1 in 3 – are at risk of fluvial or pluvial flooding. When isolating fluvial risk alone, 22.6 million properties are exposed.
Notably, 78% of fluvial-risk properties identified by JBA fall outside FEMA-mapped SFHAs, a much higher figure than estimates of 20–25% of NFIP claims coming from outside SFHAs. Furthermore, 33% of buildings within FEMA zones are shown to be not at risk under the JBA model – demonstrating its granularity and advanced simulation capabilities.
Houston case study: A closer look
As seen in central Houston (Figure 2), while FEMA flood zones broadly capture the core of JBA’s 100-year flood extent, JBA’s maps reveal far more detailed flood pathways – aligning with infrastructure such as roads and railways. In fact, JBA’s 100-year fluvial map identifies 10.5 million buildings at risk – double the number at risk when relying solely on FEMA zones. This highlights the risk of underinsurance when using regulatory maps alone.
Terrain and elevation: Critical for accuracy
The strength of JBA’s model is largely attributed to its use of high-resolution terrain data, which is essential for capturing the true flow of inland floodwaters. Combined with its pluvial flood capability, this delivers a much more complete assessment of inland flood risk.
State-level insights
At the state level, the model shows significantly elevated flood exposure in southern states – particularly Louisiana, Florida, and Texas – where over 40% of buildings are exposed. As shown in Figures 3 and 4, coastal and hurricane-prone states dominate the top 10, but several inland and western states – including California, North Dakota, and Delaware – also appear among those most at risk. This reflects the combined influence of tropical systems, convective rainfall, and snowmelt-driven flooding across different regions.
Overall, the results highlight that flood risk extends far beyond traditional coastal zones: all but six states show more than 20% of properties at risk, underscoring that flood exposure is a truly nationwide concern.
Closing the flood protection gap
While the NFIP has laid a critical foundation for national flood resilience, its limitations in spatial resolution and flood type coverage leave millions of properties unprotected. JBA’s US Inland Flood Model addresses these gaps with unmatched data quality and probabilistic modelling capabilities.
For private insurers and reinsurers, this model offers a powerful opportunity to:
- Extend flood coverage into underserved areas
- Enhance pricing accuracy with granular risk data
- Support national resilience by offering viable alternatives to NFIP-only strategies
As flood risks grow under climate change and urbanisation, tools like JBA’s Inland Flood Model are essential – not just for better insurance decisions, but for a safer, more resilient future.
Explore how JBA’s Inland Flood Model can support your flood underwriting, risk transfer, and product development goals.