Understanding Detention vs. Retention Ponds in Stormwater Management

Two methods of managing stormwater are the utilization of retention ponds and detention ponds. While these terms are often used interchangeably, there are distinct differences between the two types of constructed basins. A main difference is the presence or absence of a permanent pool of water.

Detention Ponds
A detention pond, also known as a dry pond, is an excavated basin that collects and temporarily detains stormwater runoff to prevent flooding and downstream erosion. Particles and pollutants are allowed time to settle, and filtration can sometimes be added to improve water quality, but water treatment options are otherwise limited. Detention ponds can be dry between rainfall events.

Retention Ponds
Also known as wet ponds, retention ponds are designed to hold a pool of water indefinitely to control stormwater runoff. Retention ponds are very effective at pollutant removal that occurs naturally through the settling of sediments and natural biological activity. They offer more aesthetic appeal than detention ponds, provide a habitat for fish and wildlife, and can be used for recreational purposes.

Site Feasibility and Design Considerations
Civil engineers take numerous considerations into account when determining the feasibility of both dry and wet ponds, including drainage area, slope, soil, topography, and groundwater tables. Design specifications, which are largely influenced by client or community preferences, site constraints, regional climate, and local regulations, include stormwater pretreatment, water treatment design features, conveyance, maintenance requirements, and landscaping.

Cost and Maintenance Comparison
According to the Environmental Protection Agency (EPA), construction costs associated with detention ponds and retention ponds are quite similar. On average, dry pond maintenance costs tend to be slightly higher than comparable wet ponds due to larger areas requiring regular mowing. Whereas detention ponds can often detract from adjacent property values, retention ponds are often considered desirable and can add value.

Past News/Blogs PDF's