In September 2007, a torrential flood flooded the city of Alicante and a dozen surrounding towns. The cold drop caused two rivers and several ravines in the Marina region to overflow, leaving a postcard of destruction similar to that caused by DANA this week in Valencia. The meteorological event challenged the engineers and technicians of the town hall and the company in charge of water management. “What infrastructure work can we carry out to prevent future flooding? » was the question that was asked in the following years. In March 2015, Alicante inaugurated the first flood-proof urban park in Spain.
The project was designed by an interdisciplinary group of engineers and architects. It cost 3.5 million euros, five times less than the other proposal considered, a drainage system with access to the sea, a work that required the intervention of several kilometers of urban land, including railway lines . The flood-prone park was built near San Juan beach, in the center of an urban area, on land that once formed a marsh, a wetland, close to the sea, with marshy areas covered with vegetation.
The wetland was altered and permeabilized from the second half of the 20th century with the construction of large urban developments, which caused drainage and flooding problems. “The ecosystem functioning of the wetland was taken as an example and a large park, full of biodiversity, with a storm basin was designed, in easy to explain terms, with a storm basin,” explains Luis Rodríguez Robles , former director of Town Hall Services and Projects, participant in the project.
In its technical definition, a floodable park is a facility with the capacity to store and delay the runoff of rainwater during episodes of intense precipitation. “It’s a nature-based solution that helps cities become sponges,” describes Miriam García, landscape architect, founder and director of a sustainable urban design laboratory.
La Marjal Park has 3.6 hectares of floodable area with a capacity to trap up to 45,000 m3 of water. It has two collectors, located on adjacent avenues prone to flooding, which collect flood water and channel it towards the park reservoir. The collected flow is then diverted to the treatment plant.
“Works. Over all these years we have managed to protect this area of the city from the impacts of torrential rains,” explains the company Aguas de Alicante. In August 2019, for example, Alicante recorded its highest summer rainfall never recorded. The urban park has stored 22,000 m3 – half of its maximum capacity – the equivalent of 12 Olympic swimming pools two meters deep.
In addition to its hydraulic function, the park preserves biodiversity by serving as a refuge for the region’s vegetation and bird species. Over these nine years, it has become a resting place for many species of birds migrating to Africa.
In August 2019, Alicante recorded its highest summer rainfall since records began. The urban park has stored 22,000 cubic meters – half its maximum capacity – the equivalent of 12 two-metre-deep Olympic swimming pools.
Two types of flood-prone parks
Miriam García, director of Landlab, a Barcelona studio that has won several awards for its resilient urban projects, explains that there are two types of flood-prone parks: on the one hand, there are those that serve to retain water during periods of flooding and overflowing of rivers. and streams, built near and adjacent to these watercourses. The Zaragoza water park, projected on an ancient alluvial forest located on the left bank of the Ebro, is an example. “They are built near and adjacent to these waterways, so that when a DANA occurs like the one this week and the river flow increases, the floodplain is inundated. “We manage to contain the river and make it overflow where we want,” he explains.
But this expert also adds that there are flood-prone parks in cities that function as sustainable drainage systems. “These parks are designed to control urban flooding, when drainage infrastructure is not able to handle more rainwater, which we also saw with this week’s DANA,” he points out.
Alicante is the best-known example. But there are other smaller ones, like the Plaza de Enric Granados, in Barcelona. As part of the Superblocs program, this green space was equipped with reservoirs to store rainwater, which absorb 89% of surface runoff. Why are these projects not spread across the entire territory? “Because of land conflicts,” replies García.
“A flood-prone park doesn’t mean much. It occupies a space in the city that, in general, we try to make profitable with urbanizable projects. When looking for water solutions, public administrations look for shortcuts, faster and more traditional mechanisms. The problem is that these shortcuts are intended for certain rainfall parameters. When it rains much more than expected, the work fails and we face disasters,” he explains.
“A flood-prone park doesn’t mean much. It occupies a space in the city that, in general, we try to make profitable with urbanizable projects. When looking for water solutions, public administrations look for shortcuts. The problem is that these shortcuts are intended for certain rainfall parameters. When it rains much more than expected, work fails and we face disasters.
Myriam Garcia
— Director of the LandLab studio in Barcelona
The lack of urban regulation in flood-prone areas – the provinces of Valencia, Alicante and Murcia have 280,000 housing units on these lands – is “another problem”, explains the architect. The new climatic reality, with increasingly extreme precipitation, should generate “a reconsideration of developable land in floodplains”.
“We should remove these urbanization projects and create flood-proof peri-urban parks at the entrance to cities. Unfortunately, we continue to rely on concrete,” laments García.
A flood-prone park for Los Alcázares, in Murcia
Javier Sánchez is Deputy Director General of Water Protection and Risk Management, an office that reports to the Ministry of Ecological Transition and Demographic Challenge (Miteco). He is one of the engineers who participated in a flood park project in Murcia which already has all the administrative permits and is awaiting a tender.
According to the map that identifies areas with significant potential flood risk (ARPSI), Los Alcázares (19,000 inhabitants), on the banks of the Mar Menor, is one of the towns in the country most at risk of serious flooding. .
The last disaster occurred in September 2019, when waters buried its historic center. To prevent this tragedy from happening again, the Government has designed a flood-proof park on 29 hectares of agricultural land.
The future park will be able to contain up to 400,000 cubic meters of water. A system of four canals will be constructed to deliver the first runoff water in an orderly manner in the event of heavy rains. All margins will be vegetated (45% additional specimen trees will be planted) and an impermeable covering capable of resisting the greatest runoff will be laid.
The official says that at the beginning, the project received a lot of rejection from the city’s political authorities. “We had to convince a lot of people. I dare say that 99% of mayors are convinced that by cleaning rivers and creating swamps, the risk of flooding is eliminated. They ask us to clean and raze the entire area to leave the rivers as canals. This is what you shouldn’t do. We need to plant trees and reclaim spaces, increase riparian vegetation, increase biodiversity and achieve more permeable cities with sustainable urban drainage,” he summarizes.
Some objections
José Damián Ruiz is professor of physical geography at the University of Malaga and specialist in water resources. According to him, a flood-prone park “makes sense” in certain areas.
“It’s not a one-size-fits-all solution. The key is knowing where you can build a flood-proof park. The geomorphological and orographic configuration is determining,” he explains. The Murcia project, he points out, would be impossible in Malaga – another province that suffered the impact of DANA – with a mountain flowing into the sea.
“Runoff has a spectacular acceleration. With this transportation capacity, it is not possible to simply carve out an area to create a flood park with storage tanks. Each site has its own water solution. Be careful not to fall into generalities,” he explains.
For Ricardo Aliod, professor of hydraulic engineering and irrigation at the School of Agronomists of Huesca and member of the New Water Culture Foundation, neither flood-prone parks nor any other urban adaptation measure are effective in the face of a DANA like the one that hit Valencia. .
“There is no possible protection against an event like this,” he emphasizes. According to him, policymakers continue to ignore the causes that intensify extreme weather events around the world. “It is estimated that the economic impacts of reducing emissions are less than the material damage and human lives. Adaptation then becomes more and more difficult,” he laments.
“I wonder: how many farmers in Almería who saw their greenhouses destroyed by hail this week argue that the 2030 Agenda and environmentalism are to blame? A water expert, Aliod celebrates urban projects with sustainable drainage systems. But he insists that we must first focus on the causes of the climate emergency: “Be careful not to create false placebos.”
