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 what DANA caused this week in Valencia. The meteorological event challenged the engineers and technicians of the city council and the company in charge of water management. “What infrastructure work can we carry out to avoid future floods?” was the question that was put on the table in the following years. In March 2015, Alicante inaugurated the first floodable 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 that was considered, a drainage system with access to the sea, a work that required intervening several kilometers of urban land, including the railway tracks. The flood park was built a short distance from San Juan beach, in the center of an urban area, on land that, in times past, formed a marsh, a humid area, close to the sea, with swampy areas covered with vegetation. .
The wetland was altered and permeabilized starting in 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 tank was devised, in easy-to-explain terms, with a storm tank,” explains Luis Rodríguez Robles, former head of the City Council’s Service and Projects, participant in the project.
In its technical definition, a flood park is a facility with the capacity to store and delay stormwater runoff in episodes of intense rainfall. “It is 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 surface with the capacity to trap up to 45,000 m3 of water. It has two collectors, located on the adjacent avenues with a tendency to flood, which collect the water from the floods and channel it to the park tank. The collected flow is then diverted to the wastewater treatment plant.
“Works. In all these years we have managed to protect that area of the city from the impacts of torrential rains,” the Aguas de Alicante company explains. In August 2019, for example, Alicante recorded its biggest summer rainfall on record. The urban park 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 species of vegetation and birdlife in the region. In these nine years, it has become a resting point for many species of birds that migrate to Africa.
In August 2019, Alicante recorded its highest summer rainfall since records began. The urban park stored 22,000 cubic meters – half of its maximum capacity – the equivalent of 12 Olympic swimming pools two meters deep.
Two types of flood parks
Miriam García, director of Landlab, a Barcelona studio with several awards for its resilient urban projects, explains that there are two types of flood parks: on the one hand, there are those that serve to retain water in periods of flooding and overflowing of rivers and streams, built near and adjacent to these watercourses. The Zaragoza Water Park, which was planned on an ancient alluvial forest, located on the left bank of the Ebro River, is an example. “They are built close to and adjacent to these watercourses, in such a way that when a DANA occurs like this week’s and the flow of the river increases, the floodplain is flooded. “We manage to contain the river and we make it flood where we want,” he details.
But also, this expert adds, there are flood parks within cities that function as sustainable drainage systems. “These parks are designed to control urban flooding, when drainage infrastructures are not capable of supporting more rainwater, something we also saw with this week’s DANA,” he emphasizes.
Alicante is the best known example. But there are other smaller ones, like the Plaza de Enric Granados, in Barcelona. Within the framework of the Superblocks Program, this green space added tanks to store rainwater, which cushion 89% of surface runoff. Why are these projects not spread throughout the country? “Because of the disputes over the land,” García responds.
“A flood park has little business. It occupies a space in the city that, in general, attempts are made 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 planned for certain rainfall parameters. When it rains much more than expected, the works fail and we are faced with catastrophes,” he explains.
“A flood park has little business. It occupies a space in the city that, in general, attempts are made to make profitable with urbanizable projects. When looking for water solutions, public administrations look for shortcuts. The problem is that these shortcuts are planned for certain rainfall parameters. When it rains much more than expected, the works fail and we are faced with catastrophes
Miriam 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 homes on these lands – is “another problem,” says the architect. The new climatic reality, with increasingly extreme rainfall events, should be generating “a reconsideration of developable land in flood plains.”
“We should be removing these urbanization projects and creating flood-prone peri-urban parks at the entrance to the cities. Unfortunately, we continue to rely on concrete,” García laments.
A floodable park for Los Alcázares, in Murcia
Javier Sánchez is deputy director general of Water Protection and Risk Management, an office that depends on the Ministry for the Ecological Transition and the Demographic Challenge (Miteco). He is one of the engineers who has participated in a flood park project in Murcia that already has all the administrative permits and is pending bidding.
According to the map that identifies the Areas of Significant Potential Risk of Flooding (ARPSI), Los Alcázares (19,000 inhabitants), on the edge of the Mar Menor, is one of the towns in the country with the highest risk of suffering severe flooding.
The last catastrophe occurred in September 2019, when water buried its historic center. To prevent the drama from happening again, the Government designed a flood-prone park on 29 hectares of agricultural land.
The future park will be capable of containing up to 400,000 cubic meters of water. A system of four canals will be built to conduct the first runoff waters in an orderly manner in an episode of heavy rain. All the margins will be greened (45% more tree specimens will be planted) and an impermeable pavement capable of withstanding the greatest runoff will be laid.
The official says that, at first, the project generated a lot of rejection from the town’s political authorities. “We have had to convince a lot of people. I dare say that 99% of the mayors are convinced that by cleaning the rivers and creating some swamps the risk of flooding is eliminated. They ask us to clean and raze the entire area to leave the rivers as canals. It’s what not to do. We must plant trees and recover spaces, increase riverside vegetation, increase biodiversity and achieve more permeable cities with sustainable urban drainage,” he summarizes.
Some objections
José Damián Ruiz is a professor of Physical Geography at the University of Málaga and a specialist in water resources. In his opinion, a floodable park “makes sense” in certain territories.
“This is not a universal solution. The key is where you can build a flood park. The geomorphological and orographic configuration is a determining factor,” he explains. The Murcia project, he clarifies, would be impossible in Malaga – another province that suffered the impact of DANA – with a mountain rushing into the sea.
“Runoffs have a spectacular acceleration. With this hauling capacity, it is not possible to simply delimit an area to create a flood park with storage tanks. Each site has its water solution. Be careful not to fall into a generality,” he clarifies.
For Ricardo Aliod, professor of Hydraulic and Irrigation Engineering at the School of Agronomists of Huesca and member of the New Water Culture Foundation, neither flood parks nor any other urban adaptation measure is effective in the face of a DANA like the one that has hit Valencia. .
“There is no possible protection against an event like this,” he points out. In his opinion, decision makers continue to ignore the causes that are intensifying 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 increasingly difficult,” he laments.
“I wonder: how many of the farmers in Almería who saw their greenhouses destroyed by hail this week maintain that the 2030 Agenda and environmentalism are to blame?” As an expert in water matters, Aliod celebrates urban projects with sustainable drainage systems. But he insists that first we must focus on the causes of the climate emergency: “Be careful with creating false placebos.”
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