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Manhattan, Venice or Cartagena de Indias. For the inhabitants of these tourist centers it is increasingly clear how sea levels have swallowed up part of their bays. In the case of the Colombian locality, the latest scientific studies have recorded an average annual increase rate of seven millimeters for two decades. This is the second highest water elevation in the entire Caribbean, surpassed only by areas of southern Haiti. The backstory repeats itself: greenhouse gas emissions have accelerated the melting of the polar ice caps. Soon after, in some of these places, the coasts begin to sink, in a geological process that poses a threat and burden to neighbors.
The case of Cartagena, however, is not entirely attributable to climate change. There are other unavoidable realities. “41% of relative sea level rise is due to geology,” explains marine biologist Juan Darío Restrepo. “It’s nature and we can’t do anything about it. For example, one of the bay’s biggest problems is that it has more than 80 volcanic underwater gas holes. When they erupt, they spit out all the mud and release pressure, leaving empty pockets that cause cracks. As a result, the city’s ground sinks.”
Hurricane hits Melissawhose eye was formed in Jamaican waters, provide a good example of the impact of these phenomena on daily life in the Colombian Caribbean: the avenues bordering the seafront were flooded; Families in low-income neighborhoods like El Lebanon have reported emergencies; The lobbies of some hotels were submerged in water, while other car parks of more affluent buildings in the Bocagrande sector were affected by water.
Recent torrential rains and storm surges have served as another wake-up call to remind authorities of the city’s vulnerability. Juan Darío Restrepo explains that, previously, the season of strong winds and rough seas was concentrated in the first quarter. There were no more than two or three serious floods: “Now there are around 15 per year. It was a phenomenon that once was almost never felt in the city. Today, with those few millimeters of sea level rise, and a high tide of 50 centimeters more, the water table rises and with them the waves too.”
The other part of the mess occurs in the bay and is related to the progressive compression of the land. This geological phenomenon is called “subsidence”. This is a process that has accelerated in other cities such as New York, where the weight of its skyscrapers causes a sinking of between one and two millimeters per year. In Cartagena, a study published in 2022 in the journal Scientific reports (from the same publisher as Nature) by a group of ten scientists warns that, by 2050, the decrease will be 8 millimeters per year if some measures are not taken.
To the list of factors, in addition to the weight of the buildings, another is added: Cartagena de Indias’ water system uses a network of pipes and canals and marshes that flow into the bay. These bodies of water carry sediment that has consolidated over decades in areas such as the old city. Héctor Mora, a geodesy specialist and co-author of the study, says more data is needed to definitively determine the impact of increased rainfall or groundwater and wastewater management. What solutions exist to mitigate wave advance and subsidence?
The authorities of Cartagena de Indias, a city with old problems of political corruption, have opted for rock spurs to stop coastal erosion. However, Restrepo points out that, due to the sandy and muddy composition of much of the bay’s subsoil, these walls represent a harmless solution: “It’s the best way to bury money.” Shimon Wdowinski, doctor of geophysics and academic at Florida International University, brings to the table the case of Miami, where state authorities opted for other options because the city was built on limestone.
In their analysis, the effectiveness of these barriers depends, to a large extent, on the geology and terrain characteristics. He points out that, in very porous soils, water always has free access to penetrate under walls and seep into cities, as if through a sponge. Juan Darío Restrepo sums up: “They can put as many stones as they want, and in four or five years the water will be on the surface again. They are shaking Cartagena in this way. And this is a way to silence the communities of Boca Chica or Tierra Bomba, who have opposed the impact of these dredging works on beach life.”
His testimony tells the social and environmental challenges of a spa full of contrasts. Declared a World Heritage Site by UNESCO, the historic center and part of the residential peninsula of Castillo Grande shine as an oasis of luxury and perfume, far from the rest of a city with alarming rates of poverty and inequality.
For now, Juan Darío Restrepo proposes some actions to begin to turn around a gray future that does not seem so distant: “The city needs a fundamental hydraulic assessment to see how to evacuate the waters. The structures and canals must be designed to defend themselves from floods. For example, we can start with all those internal canals that are behind the Castillo de San Felipe. They are all clogged with waste and bear good witness to the environmental collapse of the city. In high tourist season, the sewerage system fails to do it.” and the sewage leaves are poured into the bay. Cartagena is a diamond built at the top, but collapsed at the bottom.
