Guide to Retention Ponds

Retention ponds are by far one of the more attractive ways to handle surface runoff. They’ve been a practical solution to heavy rains since they were first introduced in the ’80s, but their popularity is surging. They can act as a buffer between natural and urban landscapes and can even assist with pollutant removal.

What Are Retention Ponds?

Retention ponds are usually built from a spillway and dam. The dam itself houses water, while the spillway redirects excess fluids during storms and floods. They rely on a perimeter levy, which prevents overflowing. They’re usually surrounded by lush grasses and plants, so they can be as beautiful as they are useful. Wet ponds collect rainwater as it escapes the watershed, then release it gradually through an orifice. This mitigates the damage of fast-flowing water and encourages evaporation before excess water has time to cause erosion.

Pros and Cons of Retention Ponds

Retention ponds are an alternative to detention (or dry) ponds. The latter technology isn’t permanently covered in water, so its aesthetics can’t compete with those of retention ponds. That said, poorly maintained retention ponds produce the same problems as any standing water. They can generate odors due to algae growth and become a breeding ground for mosquitoes. When well-maintained, they don’t produce either of these problems.

It’s relatively easy to combat algal growth. Your pond will need to be regularly pumped free of sediment. If you prefer easy maintenance, you can cope with algae bloom by planting landscaping that will reduce nutrient load. While you can certainly use herbicides, they only provide a temporary reprieve. Landscaping is a permanent solution that will ultimately reduce your maintenance load.

Detention ponds are designed to hold water temporarily, so they don’t usually require heavy water quality maintenance, but each solution suits its own unique climate. Dry ponds are best for climates that don’t produce much precipitation. In flood-prone regions, wet ponds are far more efficient at coping with runoff. Retention pond risers are built at a higher point, so they gather water from impervious surfaces. This reduces their pollutants and carries a lower risk of forming blockages. However, the rate of drainage in wet ponds doesn’t allow silt particles to settle, so they will be carried into the rest of the water cycle.

Retention ponds are often installed by property owners, municipalities, businesses, and even homeowners associations. Their benefits include:

• Design: Communities generally welcome the addition of a retention pond.
• Easy to line: This allows them to serve in regions where groundwater is vulnerable.
• Ecological benefits: Retention ponds create their own ecosystems to support life.
• Efficiency: Wet ponds can cope with the heaviest storms.

However, no stormwater solution is perfect, and retention ponds are no different. Their downsides include:

• Anaerobic conditions: If they don’t experience regular inflow, water can support algae blooms and mosquitoes.
• Increase in invasive species: Wet ponds create a new ecosystem, which could support unwelcome plant life.
• Need for space: Wet ponds don’t suit built-up urban areas.

iSTORMWATER can help you to find the best solution for your unique region and priorities. Our team has a variety of certifications to cover the breadth of our services. We offer a wide range of flood mitigation solutions and install both above and belowground facilities.

Contact us to arrange a consultation at 443-699-2828.