A city that floods on top of a river

When we were first investigating Barranquilla, we kept getting stuck on a contradiction—here is a coastal city, whose bodies of water help define its identity. On one side, the mouth of one of South America’s largest rivers, the Magdalena. On the other side, the vast coast of Caribbean Sea hugs the north of the city, along with the large Ciénaga de Mallorquín swamp. And yet, every wet season, the streets flood so badly, not from these large bodies of water, but from a system of creeks the city built over part of its growth. The residents have given the floodwaters their own name, Arroyos. Cars get swept down avenues. Bus routes shut down. People drown.

In a city with such a flooding issue, we were shocked to learn that only about 17% of Barranquilla’s wastewater is treated. Roughly 83% of the sewage produced by a city of more than a million people flows directly into the same rivers and wetlands that define its geography.

Barranquilla’s water story is not really defined by scarcity or a city that needs more water. It’s about a city that has lost track of where its water goes when it rains, and where its wastewater goes when it doesn’t. Our intervention tries to rebuild that connection. Not with a new pipe network but with the city’s own creeks.

This post walks through what we learned, the two challenges we chose to focus on and our proposed intervention for a network of Sustainable Urban Drainage Systems (SUDS) built along the city’s existing creek corridors.

Where is Barranquilla and why its geography matters

Barranquilla is Colombia’s fourth-largest city and its main Caribbean port. It sits about 22 km upstream from where the Magdalena River meets the sea. The land is divided hydrologically into two halves, namely the eastern slope drains directly into the Magdalena, and the western slope drains into Arroyo León and the Mallorquín Swamp. Almost everything that falls on the city eventually moves along one of those two slopes.

The climate is strongly seasonal. It barely rains from late December through April. In May, the wet season ramps up, peaking in October at almost 5 inches of rainfall in a single month. Much of that falls in short and intense bursts, sometimes 100 mm in a single day, onto a city built almost entirely of impervious surfaces.

The two challenges we’re addressing

There are five big water issues we’ve identified in Barranquilla, namely flooding, water quality, saltwater intrusion, ecosystem decline, and energy-intensive pumping. Our intervention directly addresses two of these challenges:

Stormwater flooding – Barranquilla has no real stormwater infrastructure. There are no separate storm sewer system and no stormwater master plan. When it rains, runoff simply moves downhill along the city’s streets until it reaches one of the city’s creeks (arroyos), further flowing towards the Magdalena or the Mallorquín Swamp. This leads to the flash flooding the city is internationally known for, with the worst impacts concentrated in low-lying, informal neighborhoods like La Playa and Las Flores.

Untreated wastewater discharge – Barranquilla’s drinking-water utility, Triple A (Sociedad de Acueducto, Alcantarillado y Aseo de Barranquilla), serves around 2.8 million people across the metropolitan area. Only ~17% of sewage is treated before discharge and large parts of the city including peri-urban and informal neighborhoods are not connected to the formal sewer network at all. In those neighborhoods, what does the toilet or the sink connect to? Often the creeks.

These two challenges are interconnected. The same creeks that carry stormwater are also the city’s wastewater collectors. That convergence is what makes a creek-focused intervention important and Triple A, a directly relevant partner.

Why the creeks?

Barranquilla has a beautiful natural drainage network, made up of dozens of creeks that cut through the city’s urban fabric. In a healthier urban form, these would be the city’s stormwater system and a green corridor all at once.

As Barranquilla densified, however, most of these creeks were channelized into concrete sections, narrowed or simply cut off by buildings that pushed up to the edge. This has created an unhealthy water system carrying untreated sewage from neighborhoods where sewer network doesn’t reach, solid waste from informal dumping, and stormwater with nowhere else to go.

When it rains, polluted waters, containing a mix of sewage, stormwater, and other runoff, surge, eventually reaching the Magdalena, the Caribbean, and the swamp. The creek network, therefore, is an important place to intervene. The creeks are the most visibly failing layer of the urban water system in Barranquilla. An intervention to the creek network, we believe, can help manage some of the stormwater and sewage entering the water system informally.

Learning from Bogotá

We don’t have to guess whether SUDS-along-creeks works in a Colombian city, because Bogotá has been running this experiment for the last decade.

The most directly relevant precedent is in the upper Fucha River basin. In a peer-reviewed modeling study, a SUDS package combining five detention tanks with low-impact-development features vegetated swales, rain gardens, infiltration channels, and porous pavements. This produced a 31.8% reduction in peak flow and managed roughly 2,362 m³ of runoff per event (Cipagauta-Linares et al., MDPI Water, 2025). Bogotá has also installed real, in-the-ground SUDS pilots at La Alhambra square, Avenida Córdoba, and Parque San Cristóbal, where city agencies have used the sites to study performance, maintenance, and community uptake.

 The studies on constructed wetlands under tropical conditions are relevant as they have measured BOD removal efficiencies of 79–91.5% and fecal coliform removals of 96.4–99.8% for subsurface-flow constructed wetland systems treating domestic wastewater (Arias et al.; Rivera et al.). In Barranquilla. the dominant pollution issue from urban wastewater is pathogen load rather than oxygen depletion.

The Bogotá literature also flags the right warning as a multi-sector study of SUDS adoption; the dominant barriers were not financial. They were technical and institutional with unclear responsibility for operation and maintenance and weak coordination between agencies (Cipagauta-Linares et al., International Journal of Disaster Risk Reduction, 2023). Any proposal for Barranquilla must take that seriously as the institutional landscape there is more fragmented.

The intervention: SUDS along creek corridors

Our proposal is to redesign Barranquilla’s existing creek corridors as a network of SUDS, prioritizing the segments where untreated wastewater and stormwater are converging today.

The components including adding bioswales along the creek edges to slow runoff and filter sediment and nutrients; retention ponds at strategic points to hold peak stormwater flows; permeable surfaces on adjacent streets and plazas; and constructed wetlands at points where polluted water needs partial treatment before reaching the Magdalena or the swamp. The redesigned cross-section moves the channel from a concrete trapezoid with vertical walls to a more naturalized form with gentler slopes, planted edges and floodable shoulders for wet-season peaks.

We should keep in mind that a constructed wetland inside the creek corridor is decentralized partial treatment, not a substitute for a full Triple A treatment plant. It will not turn raw sewage into drinking water. Instead, the intervention in the creeks would help reduce the load of pathogens, nutrients, and suspended solids reaching the Magdalena and the Mallorquín Swamp. Additionally, Barranquilla’s southern slope, where many of these creeks run, has low-permeability soils, meaning that the implementation of SUDS in these areas won’t dramatically increase how much water soaks into the ground. SUDS, however, can reduce peak flows and redirect it to where it can be partially treated before water reaches the river or swamp.

As part of the intervention, marsh grasses brought from the Mallorquín and other neighboring swamps would be planted along the bioswales and other permeable surfaces planned along the creeks. While it is tempting to add mangroves inland along the creeks, the level of pollution and limited amount of space would make such planting challenging. Instead, grasses, such as Cyperus sp., Carexs sp, Juncus sp., and other grasses will be planted to help stabilize polluted soils and act as a sponge for stormwater runoff. These grasses are low cost to plant and install and can do a lot of work helping repair the edges of the creeks.

Where to start?

The intervention is designed in three phases where wastewater and stormwater are converging.

Phase 1: Pilot corridors

We selected six creek segments that share three properties. xThey are in or adjacent to neighborhoods where formal sewer coverage is incomplete, they pass through residential blocks where flash-flood damage is severe, and they have enough right-of-way along the edge to add even a narrow bioswale or planted shoulder.

Phase 2: Network expansion

The pilots get extended along their full length and connected to each other where possible. A continuous corridor then moves water through a sequence of detention, filtration and discharge.

Phase 3: Citywide integration

The eastern and western drainage networks tie into the larger green-infrastructure pieces already on Barranquilla’s books like the Mallorquín Eco-park to the north, the Gran Malecón along the Magdalena and the existing mangrove restoration project in the swamp.

We want pilots in places where untreated sewage is entering the creek. That’s where the constructed-wetland piece does its most work and where the public-health benefit is most visible.

Partners, Financing and the role of Triple A

Triple A is the most important partner. Their full mandate covers Acueducto (drinking water), Alcantarillado (wastewater/sewerage), and Aseo (waste collection). They are the legal operator of the wastewater system whose underperformance we’re trying to address. A successful intervention, reducing the volume of untreated sewage entering the creeks, can serve as one improvement to Triple A’s wastewater management struggles. The per household cost of constructed-wetland treatment is plausibly lower than extending a conventional sewer network into peri-urban informal neighborhoods. Triple A also already runs Innova Social, a community engagement program for siting pilots.

The supporting partners are:

• Guardianes del Agua, a provincial program in Atlántico with the community-organizing infrastructure for building stewardship for creeks
• Barranquilla municipality, through Barranquilla Limpia y Linda (currently cleaning 51 creeks)
• Así Vivo Mi Barrio (participatory neighborhood improvement)
• Siembra Más (citywide tree planting)

For finance, Triple A and the regional government have used instruments like

• IFC’s $24M partial credit guarantee on Triple A bonds
• Atlántico governorate’s ~COP 200 billion (~USD 50M) investment in the Northern Regional Aqueduct
• Federal subsidies through the Ministry of Housing, Cities and Territory

The most useful financial precedent for this kind of intervention is the IISD/SAVi cost-benefit assessment of Mallorquín Swamp restoration. They found that nature-based infrastructure in the swamp produced more social, economic, and environmental value at lower cost than the grey-infrastructure alternative. This is consistent with the global benefit-cost ratio range of 6.35–15.0 reported for mangrove and wetland restoration projects. SUDS along creeks follow the same logic, that working with the existing landscape is cheaper than rebuilding the engineered systems.

Risks and monitoring

There are three risks that we need to consider.

Operation and maintenance

This is a barrier identified from the Bogotá SUDS literature. Bioswales clog, retention ponds need sediment removal and constructed wetlands need plant management. Without a clearly assigned and funded maintenance, the responsible entity, in our case Triple A under a renegotiated alcantarillado mandate, is at a risk of degrading within two to three years.

Unauthorized dumping

A naturalized channel is not protected from solid waste any better than a concrete one. In fact, it can be worse. Public knowledge on the importance of clean creeks and their continued maintance would be necessary, to prevent large-scale dumping from occurring in the newly cleaned creeks. The intervention must be paired with the existing Barranquilla Limpia y Linda program, not run separately from it.

Displacement

Pilot sites along creek edges are often in informal settlements where land tenure is contested. The La Loma project on the Magdalena waterfront is a cautionary example of green corridor work that displaced residents. The Phase 1 design must start from a tenure-secure baseline.

The pilot phase should track some targets

• The minimum peak-flow reduction at the corridor outfall during storm events with a target of ≥ 25% in line with the Fucha basin precedent
• Reduction in fecal coliform load entering the Magdalena or swamp with target of ≥90% reduction relative to pre-intervention baseline based on Colombian constructed wetland data
• flood-event frequency and depth in the adjacent residential blocks
• maintenance cost per linear meter of corridor.

This should be tracked annually for the citywide phase to have real numbers to scale. Monitoring is not optional and without it the pilots become anecdotes instead of evidence.

Impacts: mapping back to the challenges

Finally, we need to talk about the impacts.

On stormwater flooding

A continuous SUDS network reduces peak flow by detaining and slowly releasing rainfall. The Bogotá Fucha precedent reports a 31.8% peak-flow reduction for a comparable SUDS package. Even at half, Barranquilla would see meaningful relief in the smaller arroyos that disrupt the city.

On untreated wastewater

Constructed wetlands integrated into the creek corridor provide decentralized partial treatment for the sewage that enters creeks from unconnected neighborhoods. With BOD removals of 79–91.5% and coliform removals of 96.4–99.8% reported for Colombian tropical-climate constructed wetlands, even a modest network moves the share of wastewater receiving treatment above the current 17%. It is not a substitute for a real plant but a substantial improvement.

Naturalized creek edges create linear public spaces in neighborhoods, and they provide habitat that supports the larger Mallorquín mangrove-restoration effort downstream.

In Closing

Studying Barranquilla taught us the complexities of managing a coastal water system, where the greatest challenge is not water access, but water treatment. Interestingly, we learned how the right partner to support a nature-based intervention like ours may already be the entity whose operating mandate already covers the problem’s we’re directly addressing. Triple A’s Alcantarillado mandate would make them a co-beneficiary of our work, not an obstacle to it. Recognizing Triple A reframes the whole intervention from a planning solution into a shared interest.

Secondly, understanding the limitations of an intervention can help the implementing bodies focus on the parts of an intervention they can control. In Barranquilla’s case, while SUDS does not revolutionize stormwater treatment, when implemented at the right scale, it can greatly reduce the impacts of the existing water system. The success of other nature-based interventions in Barranquilla, including Así Vivo Mi Barrio, shows us that operating at smaller scales can lead to positive change.

Barranquilla’s creek network already runs everywhere it needs to run. The question is whether the city alongside Triple A, the province, and its residents chooses to treat those creeks as infrastructure or as liabilities.

Image sources

• Image 1,9: Authors, SUDS implemented with a vegetated edge running between houses (Google Street View imagery of Barranquilla creek channels with AI-generated visualizations (ChatGPT Images 2.0))
• Image 2, 5, 10: Maps created by Authors using based on Barranquilla water-system data from Angulo (2017) and Urban Water in Colombia (Campuzano Ochoa and Roldán, 2015)
• Image 3: Urban Water in Colombia (Campuzano Ochoa and Roldán, 2015)
• Image 4: Weather Spark
• Image 6, 7, 9: Google Street View imagery of Barranquilla creek channels.
• Image 8: Author sketches.
• Image 11: Guardianes del Agua program; Triple A Innova Social via Fundación Santo Domingo.
• Image 12: Así Vivo Mi Barrio (Ross Center for Sustainable Cities); Siembra Más.
• Image 13: Authors view of SUDS implemented with a vegetated edge running between houses and along a constructed stream (Google Street View imagery of Barranquilla creek channels with AI-generated visualizations (ChatGPT Images 2.0))

Key sources

• Angulo, J. (2017). Barranquilla’s Water Distribution System: A First Detailed Description. Procedia Engineering 186: 12–19.
• Campuzano Ochoa, C. P., and Roldán, G. (2015). Urban Water in Colombia, in Urban Water Challenges in the Americas. IANAS / UNESCO.
• Cipagauta-Linares, J., et al. (2023). “Building flood-resilient cities by promoting SUDS adoption: A multi-sector analysis of barriers and benefits in Bogotá, Colombia.” International Journal of Disaster Risk Reduction.
• Cipagauta-Linares, J., et al. (2025). “Exploring Urban Water Management Solutions for Mitigating Water Cycle Issues: Application to Bogotá, Colombia.” Water 17(13): 1992.
• Arias, C. A., et al. Feasibility of using constructed treatment wetlands for municipal wastewater treatment in the Bogotá Savannah, Colombia.
• IISD (2022). Sustainable Asset Valuation of Restoring the Mallorquín Swamp, Colombia.
• IDB Project CO-T1735: Innovative Urban Storm Drainage Systems in Colombia.
• Aranguren-Díaz, Y., et al. (2024). Aquifers and Groundwater: Challenges and Opportunities in Water Resource Management in Colombia. Water 16(5): 685.
• Acuña, Rua Díaz and Herazo. Surface water quality of the Magdalena River in the Colombian Caribbean.
• Serna-Galeano, I. A. F. Community-Based Early Warning System Model for Stream Overflow in Barranquilla.
• Sociedad de Acueducto, Alcantarillado y Aseo de Barranquilla (Triple A): https://www.aaa.com.co/
• Atlántico Governorate: https://www.atlantico.gov.co/
• IFC / World Bank PPP Resource Center: Colombia structural reforms in water.