#insights

The design and calculation of surface runoff drainage networks has undergone significant evolution over the years. Traditionally, the industry focused on rapid water removal to prevent flooding. However, with the development of new infrastructure and growing recognition of its environmental impact, the focus has shifted towards sustainable stormwater management.

Originally, the design of drainage networks relied heavily on the experience and judgment of the engineer. Over time, more systematic and quantitative methods have been developed. These include empirical, semi-empirical and physical methods that consider factors such as rainfall intensity and duration, topography/leveling of the terrain, soil permeability and vegetation cover and the capacity of the discharge point of the concentrated flow.

In this context, the application of BIM methodology is interesting, allowing the application of computational hydrological and hydraulic models that allow a more detailed and precise analysis of the design of surface drainage closely linked to the development of the infrastructure and its evolution throughout all design phases. Spreadsheet development is no longer a calculation and design option.

Today, digital tools facilitate the design and calculation of drainage networks, simulating different rainfall scenarios to evaluate the performance of drainage networks under any demanded condition, as well as the design of sustainable urban drainage systems (SUDS).

SUDS seek to imitate natural processes to manage water where it falls. They use a variety of techniques, including infiltration ditches, rain gardens, permeable pavements, green roofs, and retention ponds. These techniques reduce flow velocity, promote infiltration into the soil allowing the recovery of disappearing aquifers, improve water quality through filtration, and provide additional benefits such as green spaces and habitats for wildlife.

SUDS are part of the new sustainable development strategies, in adaptation to the environmental benefits and requirements of projects to address climate change. Designing a sustainable drainage network should include building a sponge system, which means developing a rainwater system that absorbs, stores, filters and purifies water when it rains, and releases it when needed.

The application of SUDS in urban environments achieves, among other benefits:

• Reduce the peak flow released in city streets and mitigate the levels of danger associated with high drafts and speeds in flood events, scenarios that are increasingly common in cities on the Mediterranean coast as a result of climate change.
• Reduce air pollution levels in urban environments thanks to the increase in green areas.
• Reduce the average temperature of cities by exchanging large impermeable spaces (areas covered by asphalt or concrete) for areas with abundant vegetation.
• Create spaces that contribute to urban development, not only more sustainable, but more respectful of the citizen and that favors a healthier relationship between water and the city. Rainwater runoff, traditionally relegated to being buried underground and expelled as quickly as possible, now becomes integrated with the day-to-day life of the city and creates spaces for coexistence.

Benefits of digital tools

Digital tools allow for calculations in variable regime of a drainage network, offering benefits compared to the calculation in steady state that is usually applied with spreadsheets:

• Greater precision: The variable regime takes into account the variations in flow over time, which allows a more precise analysis of the behavior of the infrastructure throughout the duration of the study rainfall.
• Modeling of complex natural phenomena: Numerical calculation models in variable regime allow us to appreciate natural flow phenomena such as contractions and dilations that occur in the network.
• Infrastructure optimization: The benefits provided by the use of complex models translate into optimizations in the infrastructures to be developed, both from the point of view of design and execution, operation and future maintenance, as well as the guarantee towards security against the risk of damage caused by an avenue.

Applying the various hydrological calculation methodologies depending on the territory, as well as the integration of the drainage system in the 3D model, are just some of the advantages of using this type of digital tools that also allow for the agile analysis of a multitude of alternatives to do more. efficient drainage.

Additionally, using a single digital tool, linking the calculation, design and 3D modeling in a single database, provides additional benefits:

• Improves the management of complex project data and information: By having all the information in a single database, access and management of project data is facilitated.
• Facilitates communication between the parties: By having all the data in one place, workflows are optimized and communication between the different project actors is improved.
• Allows to foresee and solve construction problems in advance: By being able to visualize the project in 3D and have access to all the relevant information, problems can be identified and resolved before they occur.
• Optimizes costs and work times: By having a clear vision of the project from the beginning, more accurate estimates of costs and times can be made.

The evolution of the design and calculation of drainage networks reflects a change towards more sustainable and environmentally friendly management of rainwater. SUDS play a key role in this change, providing solutions that reduce the impact associated with the development of new infrastructure, as demonstrated by recent success stories, such as that applied to the Coffs Harbor bypass in Australia, in which the team of Water Technologies of Sener has applied these types of solutions to its designs to address climate change.