Case Study: Real-Time Rain Monitoring during Heavy Rain Event in France
Rain monitoring in real-time is a difficult but crucial task. If the rain in river catchment areas is estimated accurately, floods can be forecasted more precisely and actions can be taken early on. Databourg’s proprietary rain monitoring system, PluvoLive, allows to measure precipitation in almost real-time with thousands of ground sensors that are connected to satellites. In this study, we analyze the capabilities of this novel monitoring system with respect to a recent flooding event with exceptional rainfall in the south-west of France in January 2022.
Based on rain gauge measurements and the event’s aftermath numbers published by Météo-France, we evaluated PluvoLive’s measurements and the unadjusted measurements of the OPERA radar network. Accumulated rain was measured significantly more accurately with PluvoLive in comparison to the OPERA radar data. These results indicate that it can be used to complement radar networks for improved rain monitoring in real-time. The system’s use is very promising especially in mountainous regions such as the Pyrenees where weather radars have limitations.
Exceptional heavy rain and subsequent floods in the south-west of France on January 7–10, 2022, caused tremendous damage, evacuation of hundreds of people and one fatality. Red alerts were issued for the departments of Pyrénées-Atlantiques, Hautes-Pyrenees, Haute-Garonne and Ariège. The consequence of this hydrological extreme event was a significant rise in Salat river’s water level in a way that the peak value overpassed the critical level and reached to 3.13m (the highest water level in 30 years source). The impacted regions suffered from tremendous damage.
- Rain gauges
Rain gauges are commonly regarded as the ground-truth for rain measurements. In order to measure a system’s accuracy its rain estimations are therefore compared at locations where rain gauges are in place. The data for rain gauges operated by Météo-France are publicly available here.
- Radar data
Weather radars from the OPERA network provide precipitation data (rain rate in mm/h) with a temporal resolution of 15 minutes and a spatial resolution of 2km x 2km. Available online with a license.
- PluvoLive data
The PluvoLive rain monitoring system uses data from broadband satellite terminals to measure precipitation in real-time. Spatially distributed all over Metropolitan France, it consists of more than 5000 ground terminals that enable the generation of high-dimensional rain maps with a spatial resolution of 1km x 1km and a temporal resolution of 5 minutes.
Investigation and results
This report focuses on the south-western region of France comprising the basins for the rivers Adour and Garonne. This region is subdivided into 2013 catchment areas according to the French hydrographique zones.
- Maximum Precipitation per catchment area
The first part of the investigation aimed to obtain a maximum precipitation level per catchment, thus generating a high-level rain map of the whole region that can be used for risk assessment and in the decision-making process by the responsible authorities. Due to the distribution of the 1059 satellite terminals located in the region, we are able to cover 33% of the catchments, as displayed below. Nevertheless, the remaining catchments are still covered with PluvoLive based on the integration of neighbouring values.
In the figure below, the accumulated maximum rain over 96 hours (7–10 January) is presented per catchment from PluvoLive’s and radar measurements. Despite that our sensors cover a subset of all catchment areas, it can be seen that our solution is significantly more similar in terms of detected maximum precipitation levels as officially reported (cf. image 2).
2. Total Accumulated Rain
The second part of the analysis was a point analysis, in which we focused on the locations of 2 meteorological stations (Tarbes and St. Girons, in image below), selected specifically because of the presence of rain gauges in those locations. The precipitation is shown in the following graph of accumulated rain over the course of the event. PluvoLive’s results are closer to the ground-truth rain gauge values in the vast majority of measurements.
3. Accumulated Rain in specific catchment areas
The third part of the analysis consisted in analyzing the accumulated precipitation in 4 catchments with maximum rainfall during the event (Augirein, Laruns, Aulus-Les-Bains, Arbeost). The selected regions and the precipitation levels are presented in the image and table below. As observed, our monitoring approach outperforms the unadjusted radar, and represents a significant improvement in rain measurement in this mountainous terrain.
Through this event’s report and our results obtained above, PluvoLive outperforms unadjusted radar in measuring rainfall data (especially in mountainous regions). These promising results underline the strength of AI-driven satellite signal analysis for rain monitoring in real-time. Due to its novel way of collecting rain data, the system can complement existing weather radar networks. On the other hand, in areas where radar networks are not affordable, PluvoLive could serve as one of the only comprehensive rain monitoring solutions with minimal gaps.