Detention vs Retention Pond: What’s the Real Difference?

Stormwater runoff is a serious problem. When rain falls, it flows across surfaces, picking up pollutants and overwhelming sewer systems. This can lead to flooding, erosion, and environmental damage.

To combat these issues, stormwater management systems are crucial. Two common tools in this fight are detention and retention ponds. These engineered basins are designed to control runoff, preventing it from overwhelming infrastructure and harming the environment.

But what exactly is the difference between a detention vs retention pond? This article breaks down their functions, benefits, maintenance requirements, and which one might be right for your needs.

Defining Detention Ponds

Detention ponds play a crucial role in stormwater management. Here’s a closer look at how they work:

Function and Design

Detention ponds are designed to temporarily hold stormwater runoff. Unlike retention ponds, detention ponds are usually dry, draining completely between storms. Water is removed through natural processes like evaporation or infiltration.

Advantages of Detention Ponds

Detention ponds are crucial for flood control, preventing damage to homes and buildings in the surrounding area. They are generally less expensive to build than retention ponds, making them a cost-effective solution in many situations.

Disadvantages of Detention Ponds

Detention basins often require more land than retention basins. Also, they don’t improve water quality as much as retention ponds do because the water isn’t held long enough for pollutants to settle out.

What is a retention pond?

Retention ponds are designed to improve water quality and reduce downstream flooding. They’re designed to permanently hold water, and they often have specially designed outlets or spillways that regulate the release of water.

Advantages of retention ponds

• Water quality. Retention ponds improve water quality through sedimentation and biological processes.
• Aesthetics. If they’re designed well, retention ponds can be aesthetically pleasing and even provide recreational opportunities. A fountain can improve the look of the pond and also keep the water circulating.

Disadvantages of retention ponds

• Safety concerns. Because they are designed to hold water permanently, retention ponds pose a drowning risk.
• Maintenance. Retention ponds need regular maintenance to prevent algae growth and clogging.

How are detention ponds and retention ponds different?

Detention ponds and retention ponds are similar, but they have a few key differences:

• Permanent vs. temporary water storage: Retention ponds have a permanent pool of water; detention ponds do not. Detention ponds only hold water temporarily after a storm.
• Water quality: Because retention ponds have a permanent pool of water, they’re better at removing pollutants than detention ponds.
• Maintenance: Retention ponds require more specialized maintenance to manage algae, aquatic weeds, and sediment buildup.
• Land use: Detention ponds usually require more land than retention ponds because they need a larger surface area to handle stormwater runoff.

Maintaining Detention and Retention Ponds

Both detention and retention ponds require regular maintenance to function effectively and prevent problems like flooding or pollution. Here’s a breakdown of what’s typically involved:

Detention Pond Maintenance

• Debris Removal: Clearing out leaves, branches, trash, and other debris from the pond basin and its pipes is essential to keep the system flowing.
• Erosion Control: After heavy rains, check the areas around the pond for signs of erosion, especially near the banks and inlets. Address any erosion promptly to prevent further damage.
• Vegetation Management: Keeping the vegetation around the pond trimmed and managed helps prevent overgrowth and ensures the pond functions as designed.
• Orifice Inspection: Regularly check the outlet (orifice) of the pond to make sure it’s not blocked by debris or sediment. A blocked orifice can prevent proper drainage.

Retention Pond Maintenance

• Sediment Removal: Over time, sediment builds up in retention ponds, reducing their capacity. Regular sediment removal is crucial.
• Algae Control: Algae growth can be a problem in retention ponds, impacting water quality. Control methods may include chemical treatments or introducing beneficial plants.
• Vegetation Control: Similar to detention ponds, managing vegetation is important to prevent blockages and maintain the pond’s functionality.
• Water Quality Monitoring: Regular water quality testing is necessary to ensure the pond is meeting regulatory standards and not contributing to pollution.

Design and Landscaping

Detention and retention ponds don’t have to be eyesores. Landscaping can prevent erosion and make these ponds pleasant community features.

If you’re designing a detention pond, you’ll need to consider where the water will flow in and out.

Retention ponds can be enhanced with fountains, which are both visually appealing and useful for maintaining water quality. A fountain can help prevent stagnation and algae growth in a retention pond.

Frequently Asked Questions

Putting It All Together

Detention ponds hold water briefly, while retention ponds have a permanent pool. Both types of ponds need proper design and maintenance to work well.

Stormwater management, using detention and retention ponds, is an essential part of reducing flood risk and protecting the environment.