Portuguese 
English 
Spanish 
6 min of reading 
0 comments 
Rain gardens gain space in Brazilian cities and bring the country closer to international urban drainage models, focusing on water retention, pollutant filtration, and reducing the overload on storm drains, galleries, and channels.
Brazil is expanding the use of rain gardens in urban drainage projects, a nature-based solution that already appears in policies and technical manuals of countries such as China, Denmark, the United Kingdom, and New Zealand.
The proposal is to reduce the speed with which stormwater reaches storm drains, galleries, and channels, allowing part of it to be retained, filtered, and infiltrated into the soil.
In practice, these structures function as lowered, vegetated areas, installed on sidewalks, squares, roundabouts, or road margins.
-
Women occupy bridge for over 500 days to prevent hydroelectric plant from being sold as clean energy, face cold, threats, and police, and transform Bosnian village into a global symbol of the fight for water.
-
US Government chooses sacred mountain to bury dangerous nuclear waste, faces indigenous peoples, fear of water contamination, and transforms Yucca Mountain into a symbol of environmental deadlock
-
Reservoirs in Ceará register one of the largest recharges of the decade in April 2026 and reveal a surprising scenario with intense rains, expressive volumes, and water inequality in the State.
-
The flying monster that rips a tank from the ground, flies through sandstorms, and uses 3 brutal engines that no other heavy helicopter has been able to match.
Although they look like common flowerbeds, rain gardens have prepared soil, vegetation chosen to withstand periods of flooding, and entry points to receive runoff from streets, rooftops, and impervious areas.
The difference lies in the technical role of the structure.
Instead of merely composing the landscape, the garden acts as a bioretention system, capable of temporarily storing water and reducing the volume that reaches the drainage system in a short period.
This retention is considered relevant by urban drainage specialists because floods usually occur when rain reaches the public system in a concentrated manner.
Recent experiences in Brazil indicate the gradual incorporation of this model into local policies.
In Belém, the city hall reported in February 2026 the implementation of rain gardens, stormwater planters, biowales, retention basins, and infiltration basins to reduce flooding in urban areas.
In Porto Velho, the municipal administration announced structures capable of storing thousands of liters of water during intense rain events.
Rain gardens in Brazil and urban drainage
The functioning of a rain garden depends on the combination of urban design, soil, and vegetation.
Water enters through openings next to the curb or through small channels, remains for a period in the lowered area, and then passes through layers of sand, organic compost, and substrate before infiltrating the soil.
During this process, sediments and some pollutants are retained within the system itself.
Roots help maintain soil structure, while microorganisms present in the substrate participate in natural decomposition and immobilization processes of contaminants associated with surface runoff.
This mechanism explains why the solution is treated as a complement, and not a substitute, for conventional drainage networks.
Storm drains, channels, and reservoirs remain necessary, especially in densely populated areas.
The rain garden acts before this stage, reducing the amount of water that reaches the collective system simultaneously.
In cities with soil made impervious by asphalt and concrete, this local retention can reduce the formation of flash floods on the roads.
Water no longer flows only through the gutter to the nearest storm drain but is distributed to points capable of storing and infiltrating part of the volume.
Plants used in rainwater filtration
The vegetation used in these projects does not have only an aesthetic function.
Species adapted to humidity variations contribute to stabilizing the substrate, creating pathways for infiltration, and reducing the risk of erosion within the lowered area.
The choice of plants, however, depends on the climate, soil type, and the expected maintenance frequency for each location.
In bioretention projects, plants capable of tolerating alternation between waterlogged soil and dry periods are usually prioritized.
This characteristic is important because the rain garden should not remain continuously flooded.
After the storm, the water needs to infiltrate or drain in a controlled manner so that the structure can function again in the next event.
It is also necessary to differentiate stormwater filtration from sewage treatment.
Rain gardens are designed primarily to receive rainwater mixed with road residues, such as dust, oil, leaves, tire particles, sediments, and other contaminants from urban runoff.
When there are irregular sewage connections in drainage systems or old networks that overflow during storms, rain retention can reduce the volume reaching treatment systems and watercourses.
Even so, this does not transform the rain garden into a domestic sewage treatment plant, which requires its own infrastructure and specific sanitary control.
Sponge Cities and Sustainable Drainage Systems
China incorporated the “sponge city” concept into public policies in the last decade, with projects aimed at absorbing, storing, purifying, and reusing rainwater in urban areas.
The journal Pesquisa Fapesp reports that the Chinese program reached 30 pilot cities, using floodable parks, permeable pavements, bioretention swales, and other urban drainage solutions.
In Denmark, Copenhagen began redesigning public spaces after extreme rain events caused significant damage.
One example cited in urban studies is the Karens Minde Axis, designed to function as a park on dry days and as a drainage corridor during storms, with the capacity to convey a large volume of water.
In the United Kingdom, SuDS, an acronym for sustainable drainage systems, guide the planning of new developments and infrastructure works.
In 2025, the British government published national standards for sustainable drainage focusing on reducing flood risk, storing runoff, and improving water quality before it reaches rivers and streams.
New Zealand also appears among the countries that treat bioretention as part of road design.
In Auckland, technical guides provide direction for the sizing of rain gardens and similar structures in street corridors, including recommendations on materials, maintenance, safety, and integration with public space.
Impact of Rain Gardens on Streets and Sidewalks
The installation of rain gardens can modify how sidewalks and roads handle storms.
Instead of concentrating all the water on the paved surface, the design directs part of the runoff to a vegetated area prepared to receive the temporary volume.
This change tends to reduce the speed of water in gutters and the amount of runoff flowing over the pavement.
According to technical drainage manuals, the reduction in surface runoff helps limit erosion processes, sediment transport, and wear and tear on urban areas subject to heavy rains.
The result, however, depends on the correct choice of location and maintenance.
Inlets obstructed by trash, compacted soil, inadequate vegetation, or lack of cleaning reduce infiltration capacity.
As with storm drains and culverts, system efficiency is linked to continuous conservation.
There are also physical restrictions.
Not every sidewalk can accommodate a rain garden, because the design needs to consider clear width for pedestrians, accessibility, road inclination, underground networks, soil type, and proximity to buildings.
In areas with limited space, bioretention swales, rain planters, and infiltration wells can be evaluated as alternatives or complements.
Green Infrastructure Depends on Scale and Maintenance
The adoption of rain gardens does not eliminate the need for macrodrainage works, but it adds a layer of control at the source of the problem.
Each retention point reduces a portion of the volume that would quickly reach the public system during a storm.
When these structures are combined with permeable pavements, green roofs, reservoirs, and retention basins, urban drainage begins to operate in a distributed manner.
This approach is adopted in sponge city plans and sustainable drainage systems because it acts at different stages of the water’s path.
In the Brazilian context, the expansion of the model depends on projects adapted to the local climate, soil characteristics, and the maintenance capacity of each municipality.
Without such planning, the solution may lose efficiency or turn into a degraded area within the urban space.
International experience shows that rain gardens are more effective when they are part of a network of interventions, rather than appearing as isolated works.
Be the first to react!