Authored by Bruce Eady
The image below tells a powerful story: a flood marker standing tall, with color-coded bands showing how flood stage ranges from minor to major, each representing a different level of potential impact. This marker, like others found in flood-prone areas, isn’t just a visual reminder of past flood events—it’s a critical tool for emergency preparedness and response. But how do we measure flood stage in real time? And how do we translate that data into actionable information that can protect communities?
In this blog, we’ll dive into the process of measuring flood severity, from collecting river height data to transforming it into flood maps that predict real-time impacts. By understanding this process, you’ll see how accurate flood intelligence plays a vital role in helping emergency managers respond effectively and protect lives and property during a flood.
What Flood Stage Means
Flood stages are more than just numbers; they’re indicators of the potential impact on communities and infrastructure. While the photo above visually represents flood stages using four broad categories—below minor, minor, moderate, and major—it's important to note that these definitions can vary depending on the country and the agency providing the information.
For instance:
In Australia, the Bureau of Meteorology (BoM) uses specific criteria to define flood levels in its warning service. These include thresholds tailored to Australian river systems and floodplain dynamics.
In the United States, the National Weather Service (NWS) applies its own set of definitions based on hydrological data and historical flood impacts across various regions.
Although the terminology overlaps, the thresholds for each stage and the recommended responses may differ slightly. The overall purpose remains the same: to provide clear guidance to emergency managers and the public.
Here’s a general breakdown of flood stages:
Minor Flooding: Low-level flood impact, with the possibility of some road closures and minor property damage in vulnerable areas.
Moderate Flooding: Increased risk, with greater disruption as homes, businesses, and roads could be inundated, where evacuations may be necessary.
Major Flooding: Widespread impact with severe flooding, extensive damage to infrastructure, and large-scale evacuations.
Markers like these are often updated to reflect historic flood events. For example, the flood marker notes the record flood of February 1976—a devastating event that reached an unprecedented level, serving as a benchmark for future flood planning. Having accurate, real-time data on these levels can help predict similar events, allowing for timely and effective responses.
How River Heights are Measured
FloodMapp relies on river gauges as the primary tool for measuring water levels in rivers and streams. These gauges provide real-time data that is essential for tracking flood risks as they develop.
Here’s how the process works:
Measuring Data at Regular Intervals: River gauges are strategically installed along rivers and streams to monitor water levels. These devices take measurements at regular temporal intervals, capturing the continuous rise or fall of river heights. This real-time data forms the foundation for accurate flood modeling and forecasting.
Data Transmission via Telemetry: Once the measurements are collected, the data is transmitted to a central system through telemetry protocols. This is typically done using:
Cellular networks for areas with robust connectivity.
ALERT or ALERT2 protocols, commonly used in emergency management applications for low-latency, reliable data transmission.
GOES satellites for remote locations where cellular coverage is unavailable, ensuring no data gaps in critical areas.
Integration into FloodMapp’s System: As the data arrives in FloodMapp’s models, it undergoes several stages of processing:
Quality Control: The system checks for any anomalies in the data, such as spikes or drops caused by sensor errors, and flags them for review.
Interpolation: If any data points are missing due to transmission delays or temporary gauge malfunctions, FloodMapp uses artificial intelligence (AI) to interpolate the missing data based on historical patterns and current conditions.
Outlier Removal: Erroneous outliers, which could skew flood predictions, are identified and excluded from the modeling process.
Augmenting with Contextual Data: In addition to river gauge data, rain gauges (or all-weather gauges) provide complementary information such as rainfall amounts, wind speeds, and other environmental factors. This additional context helps refine flood predictions and better understand the factors influencing flood events.
Supporting Real-Time Decision-Making: The processed data is then fed into FloodMapp’s operational system, where it powers real-time flood intelligence tools like ForeCast, NowCast, and PostCast. By combining high-quality river height data with advanced modeling techniques, FloodMapp equips emergency responders with actionable insights to make informed decisions, whether they’re pre-positioning resources, coordinating rescues, or assessing post-flood damage.
With the continuous expansion of the gauge network in regions like Williamson County in Texas, USA, accuracy has improved, providing more detailed flood data that supports proactive decision-making.
Translating River Heights into Flood Extents
Collecting river height data is just the first step. Turning this raw data into actionable flood intelligence requires advanced modeling and technology—this is where FloodMapp’s proprietary DASH (Dynamic Automated Scalable Hydroinformatics) model comes into play.
FloodMapp’s technology translates river heights into three distinct flood intelligence products:
ForeCast: This predictive model provides a view of flood extents and depths hours before the flood reaches its peak. By forecasting flooding patterns, emergency teams can plan evacuations, deploy resources, and take preventative actions to safeguard critical infrastructure.
NowCast: Updated in real-time, NowCast offers a live map of the flood extent and depth as the event unfolds. This allows emergency managers to make in-the-moment decisions, such as closing roads or mobilizing swift-water rescue teams to high-risk areas.
PostCast: After the event, PostCast provides a retrospective analysis, capturing the maximum flood extent and depth. This data is valuable for assessing damage, planning recovery efforts, and applying for disaster assistance.
For instance, during the September 2018 localized flooding in Liberty Hill, Texas, a sudden rain bomb dropped 6 inches of rain, causing the San Gabriel River to crest at 24 feet. Floodwaters inundated a nearby wedding venue, resulting in 88 people needing rescue, some from rooftops. In situations like this, having access to real-time flood intelligence can significantly reduce response times, helping emergency responders better protect lives and property.
Why Accurate Flood Monitoring Saves Lives
When a flood occurs, every minute counts. The faster emergency teams can assess the flood’s extent and respond, the better they can protect communities. Accurate, real-time flood monitoring enables emergency managers to act swiftly and decisively:
Proactive Response: By knowing potential flood extents ahead of time, emergency responders can warn residents, close roads, and coordinate evacuations before conditions worsen.
Minimizing Impact: Businesses, government agencies, and individuals can take proactive steps—such as sandbagging, moving valuables, and preparing evacuation plans—based on timely flood intelligence.
Improving Recovery: Accurate data on flood levels and impacts supports faster disaster declarations and more targeted distribution of relief resources, helping communities recover more quickly and effectively.
Flood levels are not just abstract measurements; they’re crucial indicators that help communities prepare, respond, and recover from flood events. Through real-time monitoring and advanced modeling, FloodMapp translates river heights into detailed flood maps through our proprietary DASH model that support emergency managers across the country. By using tools like ForeCast, NowCast, and PostCast, communities can stay a step ahead of flooding, reducing risk and building resilience.
Flooding will always be a challenge, but with tools like FloodMapp’s flood intelligence solutions, communities and emergency teams are better prepared to face it head-on.
Learn more about FloodMapp’s real-time flood monitoring solutions and see how they can support your emergency planning and response efforts.