Soil Erosion under extreme rainfall events: Detecting and modelling using a Radar-Runoff-Nowcasting-System

Informations projet

SED-RUNS

N° de convention de subvention: 101033236

DOI

10.3030/101033236

Projet clôturé

Date de signature de la CE 13 Avril 2021

Date de début 1 Avril 2022

Date de fin 31 Mars 2024

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 171 473,28

Contribution de l’UE

€ 171 473,28

Coordonné par

UNIVERSITA DEGLI STUDI DI FIRENZE
Italy

Periodic Reporting for period 1 - SED-RUNS (Soil Erosion under extreme rainfall events: Detecting and modelling using a Radar-Runoff-Nowcasting-System)

Période du rapport: 2022-04-01 au 2024-03-31

Résumé du contexte et des objectifs généraux du projet

Soil erosion by water is one of the most widespread forms of soil degradation in Europe. In the current context of global change, a consistent increasing of erosion is expected, principally due to a greater frequency of extreme, localized rainfall events, as predicted by recent climate models. Accelerated erosion, leading to a general degradation of the environment, depletion of soil nutrients, and agricultural areas exploitation, has become a central topic in the environmental research.
These extremes, responsible of dramatic erosion, especially in cultivated areas, have become a real challenge for agriculture and society itself. This has socio-economic repercussions due to the economic loss for damage of crops when they are affected. Awareness of the process and its extent could help stakeholders to define strategies to reduce erosion risk on a spatial dimension that is seldom considered. From society's point of view, communication of the effects during extreme events could help to increase understanding of the risk itself and improve confidence in scientific and technical resources to help people.
Focusing on a Mediterranean region, where these phenomena exist producing muddy floods and catastrophic erosion, this project aims to understand and quantify the effect of extreme rainfall by ground-radar rainfall monitoring and hydrological modelling at regional scale (Tuscany, IT). An integrated modelling approach is developed for a nowcasting-modelling-platform for runoff and soil erosion as support for warning-systems.
A relevant component in examining the effects of extreme rainfall is spatial distribution of the process. For instance, showers generally have a limited spatial extent which take place in a time spanning from few minutes to a half hour. While this dynamic is predominantly responsible for catastrophic events, it is frequently neglected in hydrological and soil erosion modelling because of missing spatial information for precipitation events. To ensure an accurate monitoring of the rainfall events, in this study, we adopted weather ground-radar, one of the most efficient methodologies. The main objective was to model the extreme rainfall events for erosion over the last 10 years with a particular interest directed at the spatial distribution of rainfall events.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

From the very beginning, special attention was given to the analysis of the available meteorological radar data and their quality. In fact, thanks to the collaboration with LaMMA, the meteorological agency of the Tuscany Region, the reconstruction of the time series of the radar records was improved by employing different methods to retrieve the precipitation from the reflectivity data (statistical and geostatistical methods). We then proceeded to select data corresponding to the extreme events for recent years.
Subsequently, the precipitation was used for the hydrological simulation for which we realized a runoff-erosion platform (ARRNS) based on the principles detailed in the project and proceeded to the steps: 1) A retrieval phase of pedological and landscape data on the regional dataset that allowed the implementation of parameters for the runoff and erosion simulation; 2) A calibration phase on the data available in a catchment area in central Tuscany (Greve-Pesa basin) using the data collected since August 2022. As the calibration area was small and little representative of the region, the reference parameters will be continuously improved during the use of the model (‘continuous calibration method’). Furthermore, baseline calibration parameters were derived from three research studies in the Mediterranean area where the model's ancestor has been effectively calibrated for similar agricultural contexts in the Mediterranean area (i.e. Sicily, France and Portugal; MASCC Arimnet2/Prima project).
The simulations of soil erosion covered the main extreme events selected over the last 10 years for erosion and runoff. We adopted as methodology that involved analyzing the distribution of the size of rainfall-cells for each precipitation in order to characterize the concentration and spatial extent of the event in relation to its intensity and on land effects (i.e. runoff and erosion). This approach we consider is the main innovation of this research and was continued for all significant extreme events, allowing processes to be characterized differently in different seasons of the year.
We then implemented a real-time erosion simulation procedure. The radar maps, made available by the National Civil Protection (DPCN), are used for runoff and erosion simulations with the methodologies described above. The simulations can be carried out once the radar data are filtered and show extreme rainfall conditions. A nowcasting procedure was also idealized, with the possibility of interpreting, from the last radar images processed in time, a little prediction for the few hours following the collection of the images.
The results and methods of the SED-RUNS has been applicated and transferred to other projects as the project: "Biodiversity and climate change in coastal wetlands: Palynological monitoring and innovative outreach approaches". Funded by EU - NextGenerationEU (PNRR, IT) which has the finality to analyse the biodiversity in Orbetello Lagoon and Burano Lake, Tuscany. Another collaboration is activated with the project GEOEVO, realized with a EAFRD co-financing from the Rural Development Programme of the Region of Tuscany. Inside this project the finality is the characterisation of geo-pedology of the olive production landscapes which constitutes a useful support for runoff erosion modelling.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

This project filled a gap in erosion modelling that had only been partially explored. Approaching such processes at this scale is a difficult race due to the problems of variability of soil properties which cannot be fully identified with respect to the process scale. In the meantime, our action is thought in a way that can be permanently improved in its calibration, a continuous input in observed vs. simulated events will be able to adapt and improve the system parameters.
The state of the art with regard to rainfall radar and erosion simulation, shows few experiences developed in very specific situations not extrapolated or disseminated elsewhere. This project has been widely disseminated in conferences and constitutes a platform capable of simulating at the required scale the process we have postulated. It is a platform working within the research group involved in national risk assessment for hydrology and we are confident of its successful use and follow-up.
The application of this research can have a positive impact on socio-economic and social implications because: i) from the point of view of knowledge of the extent of the processes, it will help stakeholders to define the extent and strategies to reduce the risk of erosion on a spatial dimension that is currently not considered. This knowledge will be useful in soil conservation policy on a regional scale to limit damage and initiate aid interventions in cases of devastating events for agricultural production. ii) From the point of view of the population's awareness of the process, this model, if applied in a communication platform by the local government, can make the population aware of what the dimensions of the process actually are and stimulate greater participation in the scientific approach to events.

Presentation_EGU_2024_Vienna