Stormwater management may not seem like a critical subject, but it is highly important for human settlement and development.
Most people are aware that the Water Cycle is a basic process that would happen with or without man’s help. It occurs when:
- Water evaporates from big water reserves (such as oceans and lakes),
- it condensates into clouds,
- when clouds meet certain conditions, it rains over a territory,
- part of the precipitation transforms into runoff that supplies rivers flows, leading to the sea,
- the rest infiltrates into the soil, recharging ground water aquifers that supply streams and watercourses towards oceans and lakes.
But since man started to populate the Earth (our home), it is no longer as simple as that. We have recently learned how important water is for us. If we plan to never run out of this precious element, we need to acknowledge that progress requires the use of water, as such impacting its availability. At the same time, modern activities contribute to water scarcity. The good news is that we can alleviate water imbalance through adequate stormwater management.
When humans settle for good, areas where they live suffer many modifications and our actions lead to consequences that interfere with the Water Cycle, which are, as sorted by importance:
- Urbanization increases surface imperviousness: There is more and faster runoff as a response to the same rainfall event ➡️ Higher flood risk.
- Urbanization decreases surface perviousness accordingly: There is less recharge of groundwater ➡️ Depletion of aquifers.
- Pollution builds up on the city’s surface: Rainfall washes away many toxic substances that poison nature, via river flows or subterrain infiltration ➡️ Water chemical contamination.
- Temperature changes: Vegetation losses and impervious surface materials lead to higher temperatures during the summer and colder values during the winter as evapotranspiration and air humidity is reduced ➡️ Thermal pollution in the atmosphere and in watercourses.
It is a fact that flooding episodes have increased around the globe over the last few decades, so humanity faces a greater flood risk than ever. Climate change has been blamed, but the truth is that deficient stormwater management is also the culprit. On undeveloped, raw terrain, natural infiltration and evapotranspiration could be as high as 90% of the total rainfall, whereas in urban areas, losses due to these two processes could be as little as 10%. This means that runoff could be up to 9 times higher! Can you imagine the devastation this would signify if we let urban areas expand indefinitely?
|Stormwater runoff is 9 times higher in urban areas vs. undeveloped, raw terrains||River flooding will increase in 85% of cities between 2050 and 2100||147M people will be hit by floods by 2030||The sea level will rise 30 in by 2100|
Furthermore, uncontrolled flooding leads to water pollution, since floods reach many areas where there are accumulations of chemicals. At the same time, when there is a huge volume of water in the same area, it becomes extremely complicated to manage. It is also highly likely that different quality (like filthy water and surface runoff) flow sources will be mixed together, and therefore the worst components will be spread to the rest. The quality of groundwater and river water, which are the main clean water sources to human life, are thus compromised.
Flood in Thailand Airport
Rivers all over the world suffer from this type of chemical and thermal pollution, and this results in environmental damage that destroys the flora and fauna of rivers and wetlands that have the ability to purify and digest some of these pollutants.
This is the vicious cycle that leads to Day Zero.
The importance of stormwater drainage
In order to deal with local flooding and wastewater drainage, drainage systems were first created more than 5,000 years ago, and these, of course, were always associated with human settlements.
Initially very primitive, such as simple brick or stone channels, they have been found in ancient cities from the Minoan, Indus, Persian, and Mesopotamian civilizations. Roman cities benefited from a relatively big development of water collection systems—a technology that was almost forgotten about until the 19th century in Western Europe, when main cities like London, Paris, and Berlin started construction of sewer systems again.
In the 20th century, this kind of water collection infrastructure grew to become a complex system, with the use of large sewer pipes, storm tanks, and wastewater treatment plants, becoming a top model in civil design and construction. However, it never addressed the main cause: the increased imperviousness of human landscapes.
So, how can we restore the water cycle back to its previous condition? The short answer is that we cannot because human settlements dramatically alter the morphology of our terrain, but we can mimic some of the aspects of natural infiltration, depuration and flow attenuation processes that happen in nature.
With the aim of source restoration and runoff control, at the end of the last century, in 1997, a new way to address stormwater excess was planned—the first sustainable drainage system to apply a full management train, including source control, was designed at a services motorway station in Oxford, England.
This kind of solution was rapidly defined as SuDS, which stands for Sustainable Drainage Systems. They are designed to manage stormwater locally (as close to its source as possible), to mimic natural drainage and encourage its infiltration, attenuation, and passive treatment.
Suds in Rio de Janeiro
They are also designed to manage flood and pollution risks resulting from urban runoff, and to contribute wherever possible to environmental enhancement. There are many different options, adapted to climate and location conditions. The four pillars of SuDS are:
- Water Quantity – Controlling the quantity of runoff to support the management of flood risk and maintain and protect the natural water cycle.
- Water Quality – Managing the quality of runoff to prevent pollution.
- Amenity – Creating and sustaining better places for people.
- Biodiversity – Creating and sustaining better places for nature.
Some of these options are:
- Permeable pavements
- Detention basins
- Retention ponds
- Rain barrels
- Green roofs
- Filter drains
- Inlets, outlets, and control structures
Combined into larger scales, a relatively new global approach to manage storm and urban water are Sponge Cities. These are, as their name suggests, designed to soak up as much extra water as possible, and are designed, or in many cases redesigned, to use a combination of storage tunnels, permeable pavements, rain gardens, constructed ponds and wetlands to store as much water as possible. They have the capacity to mainstream urban water management into the urban planning policies and designs, including the appropriate planning, legal frameworks, and tools in place to implement, maintain, and adapt the infrastructure systems to collect, store and treat (excess) rainwater.
The correct application of stormwater management leads us into water management resilience and sustainability. So how can you help? In several ways, depending on your community role:
- As an individual: By reducing and being conscious of water usage, by not littering streets and fields with your trash, so it never reaches rivers.
- As a community member: By applying green management solutions (green roofs, rain barrels, rain gardens) to your home or apartment building as soon as you have the chance.
- As a public employee or a private consultant: By demanding SuDS solutions and combining low impact developments within existing or new metropolitan areas.
Progress requires the use of water, impacting its availability. The good news is that we can alleviate water imbalance through adequate stormwater managementQatium