“Sponge City”: San Salvador uses nature to fight floods
By Jessica Troni
For World Cities Day on 31st October, we follow the story of how the United Nations Environment Programme (UNEP) is working with San Salvador city and its surrounding coffee farms to create a ‘natural’ defence against floods.
In June 2020, Tropical Storm Amanda descended on El Salvador’s capital, San Salvador. Gale-force winds and torrential rains triggered more than 150 landslides and 20 major floods, tearing apart roads, electrical lines, and almost 30,000 homes.
Coffee farmer Hector Velasquez, whose land sits on the exposed slopes of San Salvador Volcano, overlooking the city, was among those in the storm’s path. Over three days, the storm dumped two metres of rain on his farm, sparking a landslide that wiped out an area of around 3,000m2.
“The landslides take away all the crops planted in that area, so you need to reinvest,” says Velasquez, 42, a father of two. “It drains resources when resources are scarce, to begin with.”
When Velasquez was a child, rainfall in San Salvador was mostly a continuous-but-light drizzle spread across eight months. The soil had time to absorb the water. But, in recent years, climate change has made extreme storms more common in El Salvador. They are especially devastating around the capital, where rampant construction and road paving have created a concrete barrier that prevents rainfall from being absorbed into the ground.
But a movement is underway to change that. City officials and coffee farmers, with support from UNEP, have launched a project to restore 1,150 hectares of forests and coffee plantations. The goal: revive San Salvador’s ability to absorb rainfall.
In San Salvador, floods and landslides are washing away valuable topsoil, and with it the fertility of the coffee plantations. “The soil, for us farmers, is the wealth of our farm,” says Velasquez. “If we don’t have it, we don’t produce.”
Before a decline in production over the last 10 years, coffee had been vital for El Salvador’s economy, employing around 150,000 people in 2012. A report by the International Food Policy Research Institute estimates that by 2050, climate change could hit El Salvador’s coffee sector more than any other country in the world.
Enter the forest and coffee farm restoration project. Known as CityAdapt, it’s premised on a simple fact. When vegetation is replaced with concrete, the ground loses its permeability. But trees and other vegetation can be used as sponges, drawing enormous quantities of water into the earth, preventing erosion, limiting floods and recharging groundwater supplies for times of drought.
The term ‘sponge city’ is used to describe an urban area that is creating green spaces to tackle flooding. Cities around the world, from Berlin to Wuhan, are now pursuing this innovative strategy. Globally, the use of nature-based solutions for adapting to climate change is known as Ecosystem-based Adaptation.
“Ecosystem-based Adaptation is a proven strategy in both cities and rural areas,” says Jessica Troni, Head of the Climate Change Adaptation Unit at UNEP. “UNEP is helping governments around the world to build climate resilience with over 45 Ecosystem-based Adaptation projects, and in the process, over 113,000 hectares of ecosystems are being restored."
Cities adapt to climate change
CityAdapt, which is funded by the Global Environment Facility, has helped around 16,000 people in San Salvador to reduce their risk of flooding. By the project’s completion in 2022, this number is expected to rise to 115,000. CityAdapt is restoring the coffee farms destroyed by Storm Amanda, but this time with infiltrate on ditches, imitating the drainage services that streams and rivers provide naturally. It is building over 62km of infiltration ditches in San Salvador.
Leyla Zelaya, CityAdapt’s National Coordinator for El Salvador, says 3,514 fruit trees have been planted during the reforestation process to provide extra resources to local communities. The project is also active in Xalapa, Mexico, and Kingston, Jamaica.
Back on Hector Velasquez’s coffee farm, when asked what he would say to someone that doesn’t believe in climate change, he laughs: “We have a saying: There isn’t a person more blind than the one who doesn’t want to see. And there isn’t a person as deaf as the one who doesn’t want to hear.”