23.01.2025

Retention areas: Solution for heavy rainfall

Building design

Retention areas are in demand as an innovative solution for water management in relation to extreme weather events. Credit: Unsplash

In times of climate change, which is leading to more frequent and more intense heavy rainfall events, cities are increasingly affected by flooding. Innovative water management solutions are needed to minimize this risk and reduce the impact of extreme weather events. One promising measure is retention areas – natural or man-made areas that can absorb, store and release excess rainwater in a controlled manner. This article explains what retention areas are, how they work and why they play an important role in urban water management.

Retention areas are areas that serve to store excess water and thus reduce the risk of flooding. They can be natural mountain slopes, wetlands or floodplains as well as specially constructed retention basins and rainwater retention basins. These areas capture water that enters urban areas as a result of heavy rainfall, thus preventing sewage systems from being overloaded. The storage and delayed release of the water relieves the sewer systems and reduces the risk of flooding.

Retention areas are a form of so-called “near-natural water management” which, in contrast to technical solutions such as rigid wastewater systems, relies on the use of natural processes. They are not only functional, but can also offer ecological benefits, for example by promoting biodiversity and improving the microclimate in urban areas.

Retention areas work by holding back excess water from rain events to prevent flooding. This happens in several steps:

Water retention: After a heavy rainfall event, the water collects in the retention area. This can take the form of natural barriers such as rivers, dykes or retention basins. The areas are designed in such a way that they can absorb and store water over a longer period of time.
Water filtration and evaporation: In wetlands or near-natural retention areas, the water is filtered by plants. The excess water also evaporates, lowering the ambient temperature and stabilizing humidity.
Slow release: The stored water is gradually released back into the natural drainage system, preventing overloading of the sewer systems and thus flooding. This delayed release is important to avoid exceeding the capacity of urban wastewater systems.

The challenge is to find the right balance between storage capacity and release rate so that the excess water is effectively controlled without returning to the urban area and causing flooding.

In urban areas, more and more surfaces are being sealed – by buildings, roads and other infrastructure. These sealed surfaces prevent rainwater from seeping into the ground, which leads to an increased surface runoff rate. The rain cannot run off quickly enough into the sewers, which increases the risk of flooding.

This is particularly problematic in areas equipped with older sewage systems, which are often not designed to cope with the increasing volumes of water caused by more frequent heavy rainfall events. Here, retention areas can provide relief by absorbing some of the water before it enters the sewer system.

Retention areas play a key role in the resilience of cities to the consequences of climate change. By increasing the use of such areas, cities can increase their resilience to flooding and reduce the risk of damage caused by water.

There are different types of retention areas, each suitable for different urban needs and geographical conditions:

Wetlands: Natural wetlands or constructed wetlands are effective retention areas as they can store large amounts of water. They also provide a habitat for many plants and animals and help to improve air quality and the urban climate.
Retention basins: These are often built in urban areas to store water from heavy rainfall events. Retention basins are usually man-made basins or ponds that collect rainwater and release it slowly.
Rainwater retention basins: These special basins are designed to absorb rainwater from an immediate area. They are often used in new development areas to regulate the amount of water entering the municipal sewer system.
Green roofs and areas: Green roofs or planted areas on the roofs of buildings can also serve as retention areas. These areas store rainwater and release it again through evaporation and slow run-off. They therefore not only help to reduce flooding, but also provide additional green space in urban areas.
Infiltration basins: These are shallow depressions in the ground that absorb rainwater and allow it to seep into the ground. They are mainly used in areas without a high level of sealing and help to relieve pressure on sewer networks.

The integration of retention areas into urban planning requires a holistic approach that takes into account both ecological and infrastructural aspects. Here are some approaches on how this can be achieved:

Green infrastructure: cities should increasingly rely on “green infrastructure” that integrates natural elements such as parks, green spaces and water bodies to improve water management. Green roofs, vertical gardens and green facades can also serve as small, decentralized retention areas.
Use of open spaces: Undeveloped or underutilized areas such as parking lots, brownfields or riparian zones are well suited to create retention areas. By converting unused areas into near-natural, water-storing areas, these areas can serve both as retention basins and as recreational areas for the urban population.
Networking of retention areas: A network of retention areas that is integrated into the overall urban structure increases resilience to heavy rainfall. This network can be designed in such a way that rainwater is distributed over greater distances and drained away in a controlled manner.
Political and legal support: In order to promote the creation of retention areas, appropriate legal framework conditions and incentives must be put in place. This could include, for example, the promotion of new buildings with retention areas or tax benefits for owners who practice rainwater management on their land.

Retention areas are an effective and sustainable solution for combating flooding and heavy rainfall events in urban areas. They play an important role in water management by absorbing, storing and releasing excess water with a delay. Especially in cities suffering from the effects of climate change, these areas are an indispensable element of resilience. By integrating retention areas into urban planning, cities can not only relieve the burden on their infrastructure, but also improve the quality of life of their residents and make a valuable contribution to environmental protection and nature conservation.

More on the topic and our STOP THE FLOOD campaign here.

25.11.2024

Sebastian Stettner – Work assignment successful

Building design

From 1995 to 1999, the author restored five paintings from the main altar of the Franciscan church in Subotica (Hungary). The archive material available there already provided indications of the authorship of Sebastian Stettner (1699-1758). The documents in Subotica describe, among other things, the execution of the commission. According to them, Sebastian Stettner painted St. Michael “with extraordinary skill and expertise” in such a way that he […]

The documents in Subotica describe, among other things, the execution of the commission. According to them, Sebastian Stettner painted St. Michael “with extraordinary skill and expertise” in such a way that he steps on the devil. However, the client criticized the number of devils: “Why so many devils?” (Archivium 1751: 30). The artist therefore had to make changes to his painting and probably painted a completely new picture, as X-ray examinations showed no traces of overpainting. As things stand at present, he probably only submitted an oil sketch to the director of the House of the Order and chose the current iconographic concept before executing it. Unfortunately, these or other sketches by Stettner have not survived. They would have provided a better indication of his drawing skills and would have brought us closer to the art workshop where he studied.

However, by examining the materials and production techniques and evaluating the sources, a total of 14 works could be attributed to this master. The painter and gilder, whose origins are documented as “Dorst, Baijern” but could not be verified, settled in Buda (Hungary) in 1727, where he was granted citizenship in 1736. The city fathers made their decision dependent on the consent of two painters in Buda: Georg Falkoner (1646-1741) and Kaspar Landtrachtinger (1670-1744). Around 1738, his marriage to Maria Theresia Seth (1716-1789) enabled him to acquire a house in which he ran his workshop. His wife was also a painter and continued to run the workshop after Stettner’s death.
You can find out more about Sebastian Stettner’s painting technique in RESTAURO 4 / 2014.

24.12.2024

Adding a storey to a house using a 3D printer

Building design

PERI realizes the world's first residential building extension with 3D concrete printing technology in Lindau. — The PERI company is realizing the world's first residential building extension with 3D concrete printing technology in Lindau/Lake Constance. Photo: PERI

After the first residential building with 3D printing technology, PERI has now realized the world’s first residential building extension – also with a 3D printer – in Lindau. You can read all about the project here.

Following the first residential building with 3D printing technology, the company Peri has now realized the world’s first residential building extension – also with a 3D printer – in Lindau. You can read all about the project and its significance for contemporary urban development in terms of redensification here.

A few weeks after Germany’s first 3D-printed house was opened in Beckum, the Weißenhorn-based formwork giant Peri is once again making a name for itself with a project on Lake Constance. This time with the addition of a storey to a residential building in Lindau, Bavaria.

The planning architect André Baldauf is extending the residential building by one storey. What is unique about this residential extension is that the load-bearing wall structures of the new storey are applied to the existing load-bearing structure using a 3D concrete printer. For this purpose, the old roof is first removed and a concrete ceiling is placed on top. In contrast, the ceiling is still being produced conventionally, as current 3D printing processes are not yet suitable for ceilings.

This creates an additional storey on the house with a floor area of 120 square meters and a height of 3.70 meters. The insulation made of Neptune gas insulates the double-shell walls. A new timber folding roof completes the extension at the top. With this project, Peri wants to show how flexibly 3D printing technology can be used in building construction. A particular challenge in the extension project in Lindau was the slope of the property, which initially posed difficulties for those involved in setting up the 3D printer. Like the house in Beckum, the extension in Lindau is a prototype project for Peri, with which the company wants to demonstrate the possibilities of its technology.

Similar to a 3D printer for plastics, the 3D concrete printing process from Danish company Cobod used here involves applying layers of specially designed concrete on top of each other until the desired wall height is reached. This is because the printer is set up as a gantry printer. This means that the machine stands on a structure that spans the work surface. This allows the print head to move in the resulting space. The print head uses a nozzle to apply layers of concrete two centimetres high and five centimetres wide as standard.

Layer by layer, load-bearing walls are created that can follow almost any curves and curves. The layer structure creates the corrugated look of the walls that is typical of this 3D printing variant. According to the manufacturer, the printer used (BOD2) takes around five minutes to print one square meter of double-skin wall.

The concrete used is a special formulation. The manufacturer HeidelbergCement has developed this specifically for 3D printing and calls it “i.tech 3D”. It is designed for good pumpability and high green strength and allows fresh-in-fresh printing. The special concrete is said to be fully recyclable and its development focused on the lowest possibleCO2 footprint. According to the manufacturer, up to 50 percent ofCO2 emissions can be saved compared to conventional concrete construction.

The advantages and disadvantages of adding storeys to buildings using 3D printing are similar to those of 3D building printing in general. In terms of time, costs and manpower, the technology already has an advantage over molded concrete in certain areas of application. In addition, complex shapes can be realized without high additional costs. However, there is currently no way to print reinforced walls with increased load-bearing capacity. This is because the choice of materials for 3D printing of buildings is still very limited.

3D concrete printing could provide a significant boost to urban densification. Where possible, a 3D-printed extension can also be harmoniously added to complex building structures. Compared to traditional construction methods, the disruption caused to the surrounding residents by the construction work would ultimately be reduced, at least in terms of time. This could therefore pave the way for greater acceptance. In the near future, the method could also offer considerable cost savings in some cases compared to traditional formwork concrete construction.

The 3D printing of buildings is still in its infancy and is currently undergoing a rapid phase of development. We can look forward to many more innovations in this area before certain processes become established and suitable for the mass market.

You can find more information on Peri’s 3D concrete printing process on the manufacturer’s website.

Also interesting: In Hamburg, the urban real estate developer Sprinkenhof is planning an administrative building in timber construction together with ADEPT. This is set to become Germany’s largest timber building.