Early flood warning systems, an example of useful technology

On February 7, 2021, around 9:00 AM, the banks of the Alaknanda River as it passed through Girsa (Uttarakhand, India) were filled with fish displaying strange behavior. Unlike usual, they were swimming close to the surface and could easily be caught by hand. The local residents, delighted, approached the shore to fill buckets and pots with fish.

And at that moment, nothing suggested that this anomalous behavior was part of nature’s peculiar early flood warning systems. Nothing hinted that an hour later, about 70 km upstream, a disaster would unfold in the Dhauli Ganga.

What are early warning systems?

As you can see, the planet has developed alert mechanisms that, when observed closely, allow us to anticipate the advent of “something.” However, piecing together the puzzle and discovering when and how chaos will unfold is nearly impossible. That’s why early flood warning systems or other event monitoring systems that assess the most probable risks in an area are so valuable.

An early warning system (EWS) involves the integration of “surveillance processes, hazard forecasting and prediction, disaster risk assessment, communication, and preparedness activities.” Its implementation enables taking measures to reduce natural or man-made risks before hazardous events occur. It’s important to emphasize the term “taking measures.” As noted by the IFRC (1), an “early warning alone does not prevent threats from turning into disasters.” Furthermore, the term “early” carries special significance. After all, one of the main objectives, in addition to providing warnings, is to do so with sufficient time. This allows for activating actions and preventing or reducing potential damages.

These procedures can be applied in various fields. For instance, we can find early warning systems for epidemiological alerts or food safety alerts (such as RASFF, Rapid Alert System for Food and Feed).

However, our focus at Arantec is on systems related to natural hazards such as floods, avalanches, or landslides. Over time and through experience, we have developed solutions like Smarty River, Smarty Meteo, and Smarty Snow that contribute to minimizing the negative effects of these phenomena.

Components of Early Warning Systems for Floods

Although these systems are capable of monitoring various events, let’s focus our analysis on floods. After all, they are one of the most common events and their occurrence is expected to increase due to global warming. Additionally, it will allow us to see in more detail what happened in India and what the existence of an early warning would have meant. However, it should be clear that the components described below are common to all Early Warning Systems (EWS) or Community-based Early Warning Systems (CBEWS).

Risk Knowledge

Every early warning must be based on risk knowledge” (1). This is one of the guiding principles on which an early warning network is built.

This analysis, as explained by Dilma Dávila (2), requires a risk assessment that includes evaluating the threats and vulnerability of the territory. For floods, for example, it may be necessary to:

  • Conduct a hydrological and descriptive characterization of the basins and sub-basins.
  • Identify critical points.
  • Evaluate the risk in urban areas.
  • Determine the vulnerability and exposure of the population considering factors such as gender, degree of disability, access to infrastructure, etc.

In this phase, active collaboration with local communities is usually very helpful. After all, the knowledge they possess about the territory provides insights that might otherwise be overlooked.

Technical Monitoring and Establishment of Warning Systems

Once the risks are known and priorities are established, the deployment of technical instruments and human resources can take place.

Efficient monitoring activities should include:

  • Observation: This task can be carried out visually by designated individuals, but one of the best ways is through cameras that send images 24 hours a day. Automatic hydrometeorological stations can also be valuable observation tools.
  • Measurement: During this phase, measurements are taken to track what is observed. In the case of our Smarty River system, this activity is performed by periodically measuring the water level. The time intervals, configurable according to needs, can be determined based on the identification of risks.
  • Prediction or Forecasting: During this stage, future events are estimated based on observations and measurements. For example, the combination of heavy rainfall can lead to an increase in water flow during floods. And this seemingly harmless situation can result in a disaster in a population located several kilometers away.

Alert Dissemination and Communication

Deploying advanced monitoring systems is of little use if the information does not reach people in danger in a timely and appropriate manner.

As Flood Resilience reminds us, the communication of an alert should be accessible, personalized, clear, understandable, useful, and feasible. In other words, it should be tailored to the characteristics of the target audience, which requires a detailed understanding of the recipients. This aspect includes aspects such as the tone of the message and the dissemination channels (social media, SMS, loudspeakers, etc.).

The ultimate goal of effective information transmission should be to convey elements such as:

  • When the threat will arrive.
  • The impact it will cause.
  • Which areas will be affected.
  • The probability of the event occurring.
  • How the population should act.
  • Response Capacity

This element of an EWS involves developing response capabilities at the national and community levels (3). To use an analogy, the response capacity can be compared to having feet and hands. The hands would help in preparing for threats, and the feet would allow for escaping from the at-risk area.

In this phase, it is crucial to keep the population informed and trained on how to act. This knowledge is developed through emergency plans, drills, identification of evacuation routes, marking of safe zones, etc.

What would have happened in India if there had been an early warning?

At this point, let’s return to the incident in India. On February 7, a sudden flood swept the banks of the Dhauli Ganga River. The consequences were more than 200 deaths and disappearances, most of them occurring at the Tapovan hydroelectric project site.

As you can see in the attached video, created using Google Earth, it is a highly mountainous area located in the Himalayan range. The complex topography, with peaks exceeding 6,000-7,000 meters and steep slopes, makes the area prone to flash floods and landslides. The installation of early warning systems has been demanded since 2013.

Created using Google Earth. Image sources: Maxar Technologies, CNES/Airbus, Landsat/Copernicus, Data SIO, NOAA, U.S. Navy, NGA, GEBCO.

Initially, the event was attributed to a GLOF (Glacial Lake Outburst Flood). This phenomenon is usually caused by glacial lakes overflowing violently. However, detailed analysis conducted by researchers and professionals such as Dr. Dan Shugar, Dave Petley, Julien Seguinot, and Simon Gascoin, using satellite imagery from Planet Labs, Copernicus, and Airbus Space, revealed that the origin was a massive landslide equivalent to about 15 football fields in length and 5 in width. However, what happened after the landslide is still uncertain. It is not ruled out that some kind of natural damming occurred, which eventually gave way, precipitating a huge roaring mass of water downstream.


It is undeniable that an early warning system would have saved numerous lives. Cameras or sensors in the vicinity of Raini, or perhaps on the bridge that was eventually washed away, could have been used to trigger the alert. Just 5 or 10 minutes of advance notice would have been enough to warn the workers at the Tapovan construction site of the impending flood.


The incident in India once again highlights the need to invest in early warning systems to prevent tragic episodes in the future or, at the very least, minimize their consequences. With the threat of climate change exacerbating extreme weather events, this need is more urgent than ever. After all, implementing measures to protect human life is a necessity that cannot be delayed.

Sources consulted:

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