The benefits of porous pavement in drainage design

Sometimes called permeable pavement, porous pavement is an innovative and environmentally friendly approach to managing stormwater runoff in urban areas.

As cities have grown, the sheer number of impermeable surfaces like roads, parking lots, and sidewalks has only increased, leaving traditional drainage systems struggling to cope with the volume of runoff. It leads to increased flooding, erosion, and water pollution. Porous pavement, a type of Sustainable Drainage System (SuDS), offers a solution by allowing water to infiltrate through the surface and into the ground, thereby reducing runoff and promoting natural groundwater recharge. These have different names across the world like LIDs/BMPs/WSUDs – we call them SWC (Storm Water Controls) in our software – but whatever you call them, they all have the same goal: building more sustainably.

Porous pavement is designed with a permeable surface layer, which is often made from materials like pervious asphalt, pervious concrete, interlocking pavers, or even plastic grid pavers. These materials have interconnected void spaces that allow water to pass through and be temporarily stored in an underlying stone reservoir. From there, the water can either infiltrate into the soil or be slowly released into the drainage system. This approach not only helps manage stormwater and improves water quality, it has a very useful side effect of reducing the heat island effect in urban areas.

Let’s explore some of the direct benefits, as well as a few of the potential downsides of permeable pavement.

The ‘Pros’ of porous pavement

The biggest benefit of permeable pavement is that it allows for a roadway or walkway that does not increase the impermeability of a site. But there are many other “pros” to porous pavement:

• Stormwater management: Porous pavement effectively reduces surface runoff by allowing water to infiltrate through the pavement. This helps mitigate flooding and reduces the burden on traditional drainage systems.
• Groundwater recharge: By allowing water to infiltrate into the ground, porous pavement promotes the natural recharge of groundwater, helping to maintain healthy aquifer levels.
• Improved water quality: As water passes through the porous pavement and underlying layers, pollutants are filtered out, resulting in improved water quality before it reaches natural water bodies.
• Material reusability: While not yet common, it’s possible to create material by reusing by-products like slag cement from the process of manufacturing iron.
• Heat island reduction: Porous pavement can help reduce the urban heat island effect by allowing water to evaporate from the surface, which helps cool the surrounding area. It also allows tree roots to spread out, keeping them more healthy.
• Reduced maintenance costs: In the long term, porous pavements can reduce maintenance costs associated with traditional stormwater management systems, such as cleaning and repairing storm drains and pipes. This is particularly true of climates that experience frequent freeze-and-thaw cycles that can cause cracking and heaving in traditional asphalt.
• Aesthetic appeal: It almost always looks better than concrete, and you can include designs and patterns for even more visual appeal.

The ‘Cons’ of permeable pavement

As with anything, porous pavement shouldn’t be used in every situation. It does have some downsides:

• Initial installation costs: The initial cost of installing porous pavement can be higher than traditional pavement due to the specialized materials and construction techniques required. However, these costs can sometimes be offset by long-term benefits.
• Maintenance requirements: Porous pavement requires regular maintenance to ensure their permeability. This includes periodic vacuuming or pressure washing to remove sediment and debris that can clog the void spaces.
• Structural strength: Porous pavement may have lower load-bearing capacity compared to traditional pavement, making this less suitable for heavy auto traffic. Careful design and material selection are essential to ensure structural integrity. For example, this treatment isn’t suitable for slopes greater than 3%.
• Climate and soil conditions: The effectiveness of porous pavement can be influenced by local climate and soil conditions. In areas with high clay content or extreme weather conditions, a liner or underdrain may be necessary.

While porous pavement can bring some increased maintenance and need for precise soil conditions to work best, it’s becoming a more popular method for creating small, structural roadways that can handle higher inflow and infiltration rates than impermeable concrete.

Want a good example of how designers implement permeable pavement? Read about how VHB simplified and streamlined their workflows by adopting InfoDrainage.

Utilizing SuDS in InfoDrainage

When it comes to completing drainage designs for a site, it means understanding exactly how much stormwater your SuDS can handle. To do that, you need accurate and detailed hydraulic analysis for SuDS and pourous pavement systems.

InfoDrainage is a comprehensive software solution designed to support engineers and designers in creating effective and sustainable drainage systems, including SuDS like porous pavement. The software provides a range of tools and features to facilitate the design, analysis, and optimization of drainage systems, ensuring they meet regulatory requirements and performance standards.

A few reasons why InfoDrainage has become so popular with drainage designers for implementing SuDS:

• Design flexibility: InfoDrainage allows users to design custom porous pavement systems tailored to the specific needs of their projects. The software supports the creation of detailed 3D models, enabling precise planning and visualization.
• Hydraulic analysis: The software includes advanced hydraulic analysis capabilities, allowing users to simulate the performance of porous pavement systems under various storm events. This helps in assessing the capacity and effectiveness of the design.
• Regulatory compliance: InfoDrainage ensures that designs comply with local and national regulations by providing built-in guidelines and standards for SuDS, which can be incorporated into drainage reports through the flexible reporting feature. This helps streamline the approval process and ensures designs meet necessary requirements.
• Optimization tools: The software offers optimization tools that assist in fine-tuning designs for cost-effectiveness and performance. Users can evaluate different design scenarios and select the most efficient solution.
• Maintenance planning: InfoDrainage also supports maintenance planning by providing features that help identify potential maintenance needs and schedule regular inspections. This ensures the long-term functionality of the porous pavement system.

Porous pavement is a valuable component of modern sustainable drainage systems, offering numerous benefits for urban stormwater management. While there are some challenges to consider, the advantages often outweigh the downsides. With the support of advanced tools like InfoDrainage, engineers and designers can effectively implement and optimize porous pavement systems to create resilient and sustainable urban environments.

Dig into the details

• If you’re already an InfoDrainage user, our support docs can help you set every detail of your permeable paving like inlets, outlets, soil type, infiltration rate, and pollution.
• The InfoDrainage documentation covers all of the details, and these details are also covered in our free Understanding SuDS design course.
• Download our free Guide to Representing SuDS in InfoDrainage in accordance with the SuDS Manual Ciria 753.
• Want to try InoDrainage? We offer a 30-day free trial with no credit card required. Are you a student or educator? If so, we have some very good news for you.