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This article focuses on two areas of the population of Ciudad del Plata: Delta del Tigre and Penino-Autódromo. The Ministry of Environment projects for 2100, and before extreme events, that these areas could be flooded.

Approximately 200 hectares of flood plains in the Delta del Tigre area would be filled with water, displacing 3,671 people (1,908 women and 1,763 men) from their homes. In several areas the water would completely submerge homes, causing them to be temporarily vacated.

Similarly, in the 200 hectares of the Penino-Autódromo coastal area, there were 1,446 people living there in 2010, distributed evenly between women and men (720 and 726, respectively). In the event of a potential sea level rise due to climate change, 80% of the population (1,157 inhabitants) in the area would be displaced and their homes would be almost entirely underwater.

Between the two regions, 4,828 residents in an area covering 415 ha would have to be evacuated.

The Penino and Autódromo Nacional neighborhoods are characterized by simple concrete structures and smaller, informal settlements without access to sanitation. Delta del Tigre is divided between a sector of simple concrete houses and one with larger, more expensive residences with wharfs for boats of different sizes.

As the 2011 census report of the National Institute of Statistics points out, "internal migration is the component of the demographic dynamics that most heavily influences the differences in population growth observed by department. The three departments with the highest population growth between 2004 and 2011 (Maldonado, Canelones and San José) are the ones that have had a positive migratory balance since 1996, being also the only ones with a percentage of the population born in another department higher than the national average."

Continuing this trend, recent communications of the preliminary results of the 2023 census indicate a significant population increase in Ciudad del Plata as a result of population migration from Montevideo and surrounding areas, so it is highly likely that the number of people affected will exceed the expected figures.This study allows us to not only visualize how many residents will be affected by flooding, but also how their homes will be affected. The 3D model helps to identify the height of water levels on the beach, dune ridges, nature reserves, industrial areas and schools.

How it works: High resolution mapping

LiDAR (Light Detection and Ranging) is a remote sensing technology that uses pulses of laser light to measure the distance between a light emitter and an object on the Earth's surface. This technique is based on measuring the time it takes for the light to bounce off the object and return to the receiver. Reflections are recorded as millions of individual points, collectively referred to as a "point cloud," representing the three-dimensional positions of objects on the surface.

Flood mapping and simulation depends to a large extent on the accuracy of the available Digital Elevation Models (DEM). A digital elevation model is a visual and mathematical representation of terrain heights in relation to mean sea level, which facilitates the characterization of landforms and features. Surface models obtained from LiDAR systems make it possible to obtain an accurate projection of what will happen on the terrain surface given certain climatic scenarios.

A LiDAR sensor that is mounted on platforms such as drones or airplanes is known as airborne LiDAR. In this report, the water level and its lateral variations are simulated in 3D to visualize the effects of sea level rise under climate scenarios (E10 TR500) in two urban areas of Uruguay: Penino and Delta del Tigre. For this purpose, drone airborne LiDAR surveys were performed on more than 75 ha, which were used to generate DEMs, high resolution surface models, and 2D and 3D visualizations from point clouds. The DEMs were then compared with the existing models from Uruguay's Spatial Data Infrastructure-IDEuy (https://visualizador.ide.uy) and the cartographic data produced by the Military Geographic Institute of Uruguay. The E10 TR500 flood layer developed by the Uruguayan Ministry of Environment and 3m per pixel resolution satellite imagery from Planet and Google Earth were incorporated into the 3D model. For the simulation of the base sea level rise, the elevations affected by the inundation curves (NAP costas, 2019) were compared with the topography generated from the LiDAR surveys. Likewise, the most recent population data (INE, 2011) and reference sites such as educational, health and industrial centers were integrated.

Causes of flooding

Floods are the most frequent hydrometeorological events in Uruguay, caused by various phenomena.

Sudestadas: Associated with winds blowing from the south of the Río de la Plata towards the coast, these types of weather events cause increases in the river level and water inflows in the city. Coastal localities are frequently impacted by these situations.

Riverbank floods: These occur when rivers or streams overflow, either by filling their beds or by advancing towards flood plains. Urbanization is directly linked to these floods, where river floods collide with built-up areas on flood plains.

Floods due to failures of protection works: Related to levee or dam failures, these floods affect cities located downstream of such works.

Why does the most pessimistic scenario have a chance of becoming reality?

In order to analyze Ciudad del Plata, we conducted a geoprocessing analysis where we cross-referenced, through the use of Geographic Information Systems (GIS), the 2011 Population Census data of the National Institute of Statistics (INE) with the flood line published by the Ministry of the Environment, modeled for the most extreme climate scenario (E10, TR500).

The governments of 194 countries agreed in the 2015 Paris Agreement to take urgent measures to reduce greenhouse gas emissions. In doing so, they aim to ensure that by the end of the century the average global temperature does not rise by more than 1.5 °C above pre-industrial levels.

However, the measures taken so far have been insufficient. With the level of climate commitment in 2021, scientists project a temperature increase of 2.8°C by the end of the century, according to the United Nations Environment Programme's 2022 Emissions Gap Report.

The world scientific community warned that if the planet's average temperature rises by more than 2ºC, the consequences for the climate and ecosystems will be serious and irreversible.

To achieve the target, countries must consume less fossil fuels. However, CO2 emissions from burning fossil fuels and land use such as deforestation increased this year by around 1% on average, based on projections by the Global Carbon Project. The United Nations climate panel warned that greenhouse gasses would have to fall by 43% to limit global warming to 1.5 ºC and avoid the most severe impacts.

The World Meteorological Organization estimated that the average global temperature for 2022 is already 1.15 ºC higher. A temperature of such magnitude accelerates the melting of polar masses and glaciers, increasing sea levels, river courses and the occurrence of adverse extreme weather events such as droughts and floods, heat and cold waves, tropical storms and cyclones.