Researchers from the Faculty of Exact Sciences, Engineering and Surveying are studying different basins in the southern part of the province to assess areas of possible flooding.
Floods are complex phenomena that are increasingly affecting our region and, in recent years, have become a major concern in several urban and rural areas. A research team from the Department of Hydraulics and the Rosario University Center for Hydro-Environmental Research (CURIHAM) of the Faculty of Exact Sciences, Engineering and Surveying of the Universidad Nacional de Rosario, conducts studies in different basins in southern Santa Fe to see what the risks of possible flooding are and what works could be carried out to minimize the impacts.
“In southern Santa Fe, we don't have serious drought problems, so we investigate more flooding and groundwater. We focus on what we call the behavior or hydrological response of a surface runoff basin. There are several basins here in southern Santa Fe. For example, we have studied the Carcarañá River basin, the San Lorenzo Stream basin, the Ludueña Stream basin, the Saladillo Stream basin, the Frías Stream basin, the Seco Stream basin, and the Pavón Stream basin, among others; with varying degrees of progress,” explained researcher Hernán Stenta.
The professor from the Hydraulics Department explained that a watershed can be defined “as if it were an ideal line on a piece of land where all the rain that falls in that area ends up draining through canals, waterways, and so on.” That water eventually flows into a river or a lake.
He also noted that there is a lack of information at the national level for what is commonly known as watershed modeling, which aims to understand the behavior of a watershed. Therefore, these local research projects are essential, as they provide accurate data to support decision-making.
What happens when rain falls on a surface? Some of the water infiltrates the ground, while the rest remains on the surface and begins to run off. “In fields, this runoff can reach a few centimeters or tens of centimeters in height; from there it flows into the canals, from the canals to the main channel, and finally to the river. All of this dynamic (the water dynamics of a watershed) is what we study at the university using mathematical models. A mathematical model seeks to represent a real-world phenomenon through certain simplifications, with the goal of understanding the behavior of the system, which in this case is the watershed.”
There were no studies of this level in the Pavón Stream basin, so the researchers had to begin by gathering basic information about the terrain. “This work is done, for example, using the contour lines from the National Geographic Institute. Then it was necessary to collect data from the rain gauge stations to find out how much and how it fell in each part of the basin. We also gathered information on the drainage networks (ditches, roads, railways, and the main channel of the stream), as well as on the different types of soil present in the area,” the researcher explained.
With all that information, the research team built a model capable of simulating different meteorological phenomena and analyzing how water behaves within the system. “First, we carried out a calibration phase, in which we compared the observed data with the results produced by the model to verify if it accurately represents reality. Then we proceeded with a validation stage, which consists of applying the model to another rain or storm event to check if it responds similarly. Once calibrated and validated, the model can be used in the exploitation stage, which allows us to study how different climate scenarios behave,” Stenta explained.
The work was carried out in the Pavón Stream basin using the limited information available at the start of the project. Based on this initial survey, a model was developed that yielded key data on water behavior in the area. Among the most important results, the maximum water levels in different sectors of the basin were determined, allowing for the identification of the areas most affected during flood events. Water dwell times were also calculated—that is, how long a given level is maintained—a crucial piece of information for assessing the impact on crops, homes, and other infrastructure.
In addition, an indicator called “risk to human life” was incorporated, which combines water height and velocity to estimate the danger a flood may pose. “One meter of water with almost zero velocity, like in a pond, is not the same as that same height moving at one meter per second,” he explained, emphasizing that certain flow and height values can even sweep away an average adult, demonstrating the importance of having precise tools to prevent and manage water risk in the region.
Based on the results obtained, the team continues to refine its models with the aim of incorporating more precise information and delving deeper into the various factors that influence the occurrence and impact of water-related events. This approach is based on the concept of water risk, which integrates two central variables: hazard and vulnerability. “We address the hazard dimension, understood as the probability of a specific event occurring that could cause damage.”
Currently, researchers are working on the development of hazard maps that combine data on water height and speed, tools that are fundamental for planning and decision-making by government agencies, basin committees and civil defense areas.
These studies help us understand that the same threat can have very different consequences depending on the territorial and social context. “One meter of water, for example, does not imply the same risk in an area with solid buildings as in one with precarious housing,” Stenta stated.
With this perspective, the team is expanding its work to different watersheds where it is developing new hazard maps. “We continue working in Pavón and other watersheds, such as Arroyo Seco and Pueblo Esther, always with the aim of explaining the hydrological behavior of each one. The goal is to obtain models that reflect reality and that can then be applied to the creation of hazard, vulnerability, and risk maps, available to the public and useful for decision-making by government agencies. Furthermore, this information allows for more efficient planning, identifying, for example, which areas would be dangerous to develop due to the presence of low-lying areas with high concentrations of water and, therefore, a higher level of risk,” the researcher explained.
The larger a weather event, the greater the effects of flooding. The most affected areas are usually those near waterways or in low-lying areas. Stenta emphasized that these phenomena depend largely on the magnitude of rainfall, which, in the context of climate change, has shown a change in its behavior: a greater concentration of severe storms is observed in shorter periods of time.
While the average annual rainfall in Rosario remains relatively stable, between 1,000 and 1,110 millimeters per year, there are significant variations from year to year. “There is no clear upward trend, but rather a change in the distribution and intensity of storms. In recent years, extreme events have been recorded, such as those in Bahía Blanca, Zárate, Arroyo Seco in January 2017, and La Emilia, where a landslide caused serious damage.”
In addition to this natural component, there is the impact of human activity. The urbanization of areas that were once green and soil transformations through practices such as no-till farming have increased the territory's vulnerability. "Together, these factors generate a greater impact during storms, as was recently evidenced in various watersheds, including the Carcarañá, which also suffered the effects of the most intense rainfall recorded this year."
Journalist: Gonzalo J. García