Wet Detention Ponds vs. Dry Detention Basins: Which Should an Owner Choose?

KANSAS CITY — When commercial sites in the metro need surface-based stormwater controls, two options dominate the discussion: wet detention ponds (permanent pool) and dry detention basins (normally dry). Both can meet local requirements for peak-flow control, but they behave differently on your site plan, your maintenance plan, and your balance sheet. Here’s a practical, owner-focused comparison.

What they are (in plain English)

• Dry detention basin: A graded depression that temporarily stores runoff during a storm and then drains to dry. Between events, it’s typically turf or native cover.

  

  Dry Detention Basin at Smithville Price Chopper -Smithville, MO

• Wet detention pond: A basin that maintains a permanent pool of water for water-quality treatment and detention. It fills and draws down around that pool during storms.

  

  Wet Detention Pond at Heritage Tractor- Lawrence, KS

Where each shines (Kansas City context)

Dry basin — best fit when:

• You have ample land on a suburban parcel and want the lowest up-front capital.

• You can dedicate a block of surface area that doesn’t need to be revenue-producing.

• Maintenance can focus on mowing, outlet cleaning, and periodic sediment removal.

Wet pond — best fit when:

• You want a visual amenity or habitat value that can lift curb appeal (offices, hospitality, mixed-use).

• You’re targeting better water quality performance with settling time in a permanent pool (often paired with a forebay).

• You can design safety features (shelves, fencing/landscaping, slopes) and accept water-body management (algae, vector control).

Land use & site planning

• Dry basin: Typically consumes more usable surface area because the footprint must remain open and mowable. It can fragment parking fields or push buildings farther apart.

• Wet pond: Still uses surface area, but can double as open space/amenity. Thoughtful edges (walkways, native buffer, signage) can enhance the customer experience and community acceptance.

Cost & lifecycle

• Capital cost: Dry basins are usually less expensive to build (earthwork + outlet). Wet ponds cost more due to grading to support the pool, edge treatments, and forebays.

• Annual O&M: Dry basins: mowing, outlet cleaning, sediment removal on a multi-year cycle. Wet ponds: add aquatic management (algae, invasive plants), periodic dredging of the forebay, and more frequent inspections.

• Risk & reliability: Both require debris control and upstream pretreatment to manage sediment. Wet ponds tolerate small clogs better due to storage in the pool; dry basins depend on outlets staying clear to drain to “dry.”

Safety, aesthetics, and community perception

• Dry basin: Low standing-water risk, but can look like “unused land” if not landscaped. Native plantings and shaped side slopes improve appearance and pollinator value.

• Wet pond: Strong visual feature and potential wildlife habitat but introduces open-water safety considerations (shelves, fencing cues, gentle slopes, visibility) and liability planning.

Water quality

• Dry basin: Primarily peak-flow control; limited pollutant removal unless paired with upstream pretreatment (forebay, hydrodynamic separator, filter strips).

• Wet pond: The permanent pool boosts settling of suspended solids and attached pollutants, improving typical water-quality performance when designed and maintained correctly.

Owner decision framework

Choose the one that maximizes your project’s objectives:

1. If first cost rules and land is plentiful → Dry detention basin is often the owner preference.

2. If placemaking, tenant appeal, or water-quality performance are key → Wet pond can justify its higher capex as site amenity.

3. If you must preserve surface land for buildings/parking → consider Underground Detention (e.g., ADS StormTech) instead of either surface option to keep the site fully productive (See Stormwater Strategy, Part 1 & 2).