Likely, yes. An extended dry detention basin is dry most of the time and will only contain water for a short time after significant rainfall.

It may be in need of maintenance. Excessive sediment and nutrients can result in smelly, yucky ponds. Maintenance to remove these pollutants as well as preventing new pollutants is critical. Limit sediment by controlling erosion around the edges and any upstream sources. Limit the use of fertilizers and maintain an un-mowed, vegetative buffer around the pond.

You may have an extended detention wetland or an extended dry detention basin, which do not have deep, permanent pools of water like an extended wet detention basin.

Native vegetation around basins, ponds and wetlands as well as aquatic vegetation play a critical role in maintaining the health of the basins, ponds or wetlands. For a less ‘weedy’ look, consider lower growing species and adding wildflowers for color. Controlling woody and invasive species also provides a more uniform look.

Proper maintenance is the answer.

A properly maintained basin, pond or wetland will support healthy vegetation and good water quality, therefore providing an undesirable habitat for mosquitoes. A well-maintained basin, pond or wetland also provides habitat for mosquito predators like dragonflies. Mosquitoes reproduce by laying eggs in still pools of water or on mud or fallen leaves. A few inches of standing water such in dry pond depressions, voids in riprap linings, or other inconspicuous places can become mosquito breeding areas.

An unmowed vegetative buffer around the edges deters geese. Geese prefer regularly mowed grass to the edge of the water so they can see predators approaching.

Cattails are an introduced species that become invasive and choke out more desirable plants. Cattails are usually a sign of poor maintenance.

The bench, known as a littoral bench, is part of the design. It is installed for safety reasons and to allow dense stands of desirable vegetation, keeping out undesirable plants like cattails. It also provides habitat for insects (mosquito control) and takes up nutrients to prevent algal blooms.

Not all algae indicates a problem but algal blooms usually indicate an excess nutrient problem. Nutrient  input from fertilizers or pet waste needs to be controlled to mitigate the problem.

Establishing wetland vegetation within the basin, pond or wetland as well as a vegetated buffer around the edges will help improve water quality by filtering pollutants in the runoff.

This helps reduce algae growth within the basin, pond or wetland and in downstream rivers and streams. Reducing pollutants that may get to the basin, pond or wetland is important in protecting water quality. Excess nutrients, including nitrogen and phosphorus, encourage algae growth.

It may be a forebay, designed to catch sediment and pollutants before they enter the downstream lakes. In the photo to the right, the forebay for pretreatment is at the top right. It collects sediment and pollutants and allows for easier maintenance access. The extended wet detention basin is shown on the bottom half of the photo.

Native, deep rooted perennials are needed to allow for infiltration and pollutant removal. Native perennials suited to the moisture conditions of the rain garden are generally long lived and tolerate harsher conditions. Consideration should also be given to aesthetics by choosing plants with colorful blooms or foliage, seasonal interest and that fit the surrounding landscape. Shorter, more compact plants are often more acceptable. Limiting the number of species simplifies maintenance and helps discern weeds from desirable plants. Any plant that is invasive or problematic is not allowed (examples: cattails, woody brush/trees, Johnsongrass).

Native Plants

Generally, yes. The designed vegetation is critical for function and performance. With poor vegetation cover and density, the rain garden or bioretention will not perform as intended.

For a subdivision, the HOA is generally responsible for rain gardens and bioretention located on community property. Individual homeowners and business owners are generally responsible if located on private property.

No, unlike wetland and bog gardens that have a permanent pool of water except during very dry conditions, rain gardens and bioretention should be considered ‘dry’ gardens with only brief wet periods. Properly functioning rain gardens and bioretention that infiltrate standing water quickly allow for a greater selection of plants.

Rain gardens and bioretention are designed to hold water for 1-2 days. They may also be frequently inundated with repeated rain events. However, standing water beyond these conditions usually indicates maintenance to increase infiltration, clear an underdrain/overflow or remove excessive dead plant material, sediment or other debris.