Drywells, Swales, and Catch Basins: Tools of Stormwater Management

Stormwater runoff is one of the most persistent challenges small towns face. Whether it’s a sudden summer downpour or steady spring snowmelt, unmanaged runoff can overwhelm roads, erode property, and pollute nearby waterways. Fortunately, towns have a variety of simple yet effective tools to manage stormwater before it becomes a problem.

Three of the most common, and often misunderstood, tools are drywells, swales, and catch basins. Here’s a look at how each of them works, and why they matter for the health and safety of your community.

Drywells: Out of Sight, But Working Hard

A drywell is an underground structure that collects stormwater and allows it to slowly soak into the ground. Think of it as a vertical pit, often filled with stone or concrete rings, that gives runoff somewhere to go when surface drainage isn't possible.

How it works:

• Stormwater from a roof drain, roadside inlet, or paved surface is directed into the drywell.

• The water temporarily collects in the chamber.

• Over time, it infiltrates into the surrounding soil.

Best for:

• Areas with sandy or well-draining soil

• Locations where piping water away isn't feasible

• Preventing puddling in low-lying spots

Maintenance tip: Drywells need to be inspected and cleaned periodically to prevent sediment buildup and clogging.

Swales: Nature’s Drainage Ditches

A swale is a shallow, vegetated channel that conveys stormwater from one place to another, often along roadsides or between properties. Unlike traditional ditches, swales are designed not just to move water, but to slow it down and let it soak in.

How it works:

• Water enters the swale during a rain event.

• The gentle slope and vegetation reduce the water’s speed.

• Some water infiltrates the ground as it moves.

• Sediment and pollutants are filtered out by the plants and soil.

Best for:

• Rural roadsides and open spaces

• Reducing erosion and runoff velocity

• Improving water quality before it reaches a water body

Bonus: Swales can be aesthetically pleasing when planted with native grasses and wildflowers.

Catch Basins: The First Line of Defense

A catch basin is a surface-level structure, often found at the edge of roads or parking lots, that collects and directs stormwater into underground piping systems. It features a grate on top and a sediment trap below to prevent debris from entering the storm drain network.

How it works:

• Water flows over paved surfaces and enters the basin through the grate.

• Heavy debris and sediment settle in the sump at the bottom.

• Cleaner water continues through the connected storm pipe system.

Best for:

• Urbanized or paved areas

• Intersections, cul-de-sacs, and low points in roadways

• Preventing flooding on impervious surfaces

Maintenance tip: Catch basins must be cleaned regularly, especially in the fall, to remove leaves, sediment, and trash that can block flow.

Why These Tools Matter

Stormwater management isn’t just about convenience. It’s about safety, infrastructure protection, and environmental responsibility.

Properly maintained drywells, swales, and catch basins:

• Prevent road flooding and washouts

• Reduce erosion along road shoulders

• Help meet MS4 and Clean Water Act compliance

• Improve water quality by filtering pollutants before they reach streams or lakes

• Protect private property and public infrastructure from damage

In small towns, where resources are limited and every dollar counts, these systems are invaluable, offering low-cost, low-tech, high-impact solutions to everyday water challenges.

Drywells quietly absorb. Swales gently guide. Catch basins quickly collect. Together, they form the backbone of smart, sustainable stormwater management.

By understanding and maintaining these systems, towns can stay ahead of the storm and protect their roads, waterways, and residents for years to come.