Bioretention Pond Design: Effective Stormwater Management

February 28, 2024
Fish Pond Liner

Bioretention ponds have emerged as a tool in the modern landscape architect’s arsenal, blending functionality with aesthetic appeal to manage stormwater effectively. These systems not only mitigate flooding risks but also enhance water quality, making them a cornerstone of sustainable urban and suburban development. 

What Is a Bioretention Pond?

A bioretention pond is an engineered landscape feature designed to treat and manage stormwater runoff. 

Unlike traditional stormwater management systems that focus solely on diverting water away from built-up areas to prevent flooding, bioretention ponds serve a dual purpose. They slow down the flow of stormwater, allowing it to infiltrate into the ground, while simultaneously filtering pollutants through a carefully designed system of vegetation, soil layers, and sometimes, microbial action. 

This process not only reduces the volume of water that needs to be managed downstream but also improves the quality of water that reenters the aquifers or local water bodies.

Who Uses Bioretention Ponds?

Bioretention ponds are utilized by a broad range of entities, ranging from municipal governments to private developers, and even individual homeowners. 

Municipalities often incorporate them into public parks, roadside verges, and within residential areas as part of their stormwater management infrastructure. 

In the private sector, developers include bioretention ponds in commercial, industrial, and residential projects to meet regulatory requirements, enhance property values, and contribute to sustainability goals. 

Homeowners may use smaller-scale versions to manage runoff, reduce flooding risk, and improve landscape aesthetics.

When Do You Need a Bioretention Pond?

The need for a bioretention pond arises in scenarios where stormwater management is crucial to prevent flooding, erosion, and water pollution. This is particularly relevant in urban and suburban areas where natural landscapes have been replaced with impervious surfaces, leading to increased runoff. 

Bioretention ponds are also essential when:

  • Regulatory requirements necessitate on-site stormwater treatment.
  • There is a goal to recharge local groundwater supplies sustainably.
  • Landscape or site design aims to incorporate green infrastructure for environmental, aesthetic, or recreational benefits.

How Should the Pond Be Designed?

Designing a bioretention pond requires a meticulous approach that considers the specific environmental conditions and stormwater management needs of the site. Key considerations include:

  • Size and Depth: The pond should be sized based on the volume of runoff it will need to manage. This involves calculating the area of impervious surfaces draining into the pond and the typical rainfall statistics for the region.
  • Infiltration Rate: Soil analysis is vital to determine the infiltration rate, which influences the design of the pond’s base and the selection of soil media.
  • Vegetation: Plant selection is crucial for the success of a bioretention pond. Native plants that can tolerate wet conditions and are capable of filtering pollutants are preferred.
  • Overflow Mechanisms: To handle extreme storm events, the design must include overflow pathways that prevent the system from being overwhelmed while minimizing erosion and damage to the surrounding areas.
  • Maintenance Access: The design should facilitate easy access for regular maintenance tasks, such as removing sediment, managing vegetation, and inspecting structural components.

What Pond Liner is Best for a Bioretention Pond?

The choice of pond liner is critical to the function and longevity of a bioretention pond. While the natural infiltration of water into the surrounding soil is a key feature of these systems, certain circumstances may necessitate the use of a liner to prevent contamination of groundwater or to manage water levels effectively.

  • Clay Liners: In situations where natural permeability is desired but with a controlled rate, compacted clay liners can be an effective option. They provide a natural barrier that can be engineered to specific permeability standards. However, in most cases using a geomembrane liner is more effective at meeting requirements.
  • EPDM Liners: Ethylene Propylene Diene Monomer (EPDM) rubber liners are frequently used in small ponds, but most bioretention ponds are large enough that other liner materials will out-perform it by a large margin.
  • PVC Liners: Polyvinyl Chloride (PVC) liners are an economical option that offer good puncture resistance and longevity. However, they are less flexible than EPDM liners and can become brittle over time under UV exposure.
  • RPE Liners: Reinforced polyethylene (RPE) geomembranes perfect for bioretention ponds because they are mostly impermeable and prevent water leakage, which allows the stormwater to travel easily to its destination. Our Aqua series of RPE also offers a long-term guarantee.

The selection of a liner depends on the specific requirements of the bioretention pond, including budget constraints, expected lifespan, local climate conditions, and the types of pollutants expected to be present in the runoff.

Bioretention ponds represent a harmonious blend of engineering, environmental science, and landscape design. By integrating these systems into urban and suburban landscapes, communities can enhance their resilience to stormwater-related challenges while contributing to the health of their local ecosystems. Through careful planning, design, and maintenance, bioretention ponds can offer a sustainable solution to the ever-growing need for effective stormwater management.

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