Effective stormwater runoff management combines site planning, runoff reduction, treatment, storage, reuse and long-term maintenance. The right design depends on the building footprint, existing paving, soils, slope, climate, adjacent properties, intended water use and local requirements. A single feature rarely solves every problem; a coordinated mix of green infrastructure and conventional drainage is usually more resilient.
Building Design + Construction’s guidance emphasizes making water decisions early, controlling polluted runoff during construction and treating rainwater as a potential resource. Use the framework below to set project objectives, compare options and define the maintenance and approvals needed before construction begins.
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Plan the site and building together
Runoff is created by the relationship between roofs, paving, compacted soil, landscaped areas, grades and receiving drainage systems. Designing the building first and adding drainage at the end can leave no practical space for infiltration, storage or treatment. Start with a site-and-building water plan during concept design.
Review the regional climate, rainfall patterns, topography, existing drainage, adjacent properties and natural water sources. A change in grading or roof discharge can move water toward a neighboring parcel, overload a public system or carry sediment into a stream. Regional water plans and watershed objectives may also influence what the project is expected to retain, infiltrate, reuse or release.
#1 Best Overall
- BLOCKS LEAVES & DEBRIS: Protects your drainage system by preventing particles from entering and potentially clogging the pipeline while letting excess surface water flow through
- HOW TO USE: Drains heavy flows of stormwater from lawns, landscaped areas, patios, walkways, and under downspouts; water flows into a capture device connected to drain pipe to carry the water downstream to a discharge point such as a pop-up emitter
- HOW TO INSTALL: Place the storm drain grate (also known as a drain cover) on top of a capture device such as the 12 in. catch basin, riser, or low-profile adapter to drain surface water
- DESIGN FEATURES: Made of high-density polyethylene (HDPE) treated with UV inhibitors to prevent fading and cracking; available in a variety of colors, styles, and materials
- SPECIFICATIONS: 53.1 sq. in. open surface area; 162 GPM flow rate; rated for NDS Class B loads (up to 175 psi) when properly installed—recommended for medium-duty pneumatic tire traffic, autos, and light trucks at speeds less than 20 mph; ADA compliant
Map the complete flow path from each roof and paved area to its intended destination. Identify where water can be slowed, infiltrated, filtered, stored for reuse or safely discharged during storms larger than the system is designed to retain. Keep emergency overflow routes separate from everyday conveyance so a blocked inlet does not send water into occupied spaces.
Define what the system must achieve
Before selecting products or details, agree on the project’s primary outcomes. Stormwater controls may pursue one or several of these goals:
- Runoff-volume reduction: keep rainfall on site through infiltration, evapotranspiration, reuse or detention.
- Water-quality protection: remove sediment and pollutants before water reaches a drain, stream or neighboring property.
- Nonpotable reuse: capture rainfall for approved uses such as landscape irrigation, toilet flushing, washing or evaporative cooling.
- Peak-flow control: temporarily store water and release it at a controlled rate.
- Construction protection: prevent disturbed soil, concrete washout and material debris from leaving the site.
Compare each approach against available land, existing surfaces, soil and infiltration conditions, storage demand, access for inspection, maintenance staffing and local permit or code requirements. There is no universal ranking: a rain garden may be effective where land and suitable soils exist, while an underground tank may fit a constrained urban site but require more complex access and pumping.
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Compare the main stormwater strategies
| Strategy | Best suited to | Primary contribution | Key constraints or upkeep |
|---|---|---|---|
| Green roof | Buildings with suitable roof structure and access | Retains and delays rainfall near its source while adding planted surface area | Requires structural review, waterproofing coordination, plant care and safe access |
| Bioswale | Edges of parking areas, roads and landscaped corridors | Conveys runoff slowly while filtering it through vegetation and soil | Needs appropriate grades, inlets, outlet protection and removal of accumulated sediment |
| Rain garden | Landscaped areas receiving roof or paved runoff | Provides shallow storage, filtration and infiltration | Plant selection must suit wet and dry periods; grounds staff need time to maintain a diverse plant palette |
| Porous or permeable pavement | Parking, walkways and other paved areas where subgrade conditions permit | Allows rainfall to pass through the surface into a stone or soil profile | Can clog; periodic inspection and vacuuming may be required |
| Retention pond | Sites with sufficient open area and a suitable receiving landscape | Stores water and can provide treatment and controlled release | Requires land, safety measures, vegetation management and an outlet that remains functional |
| Underground storage tank | Constrained sites or projects with substantial reuse or detention demand | Stores runoff below grade without consuming surface space | Access, structural loading, pumps, controls, cleaning and overflow planning are essential |
| Direct rainwater collection | Roof areas with a practical nonpotable demand | Captures water for approved reuse instead of sending it directly to drainage | Tank sizing, screening, lids, maintenance and cross-connection protection must follow local requirements |
Many successful projects combine measures. A Building Design + Construction report on a Philadelphia community center described rain gardens, a porous athletic field, porous asphalt, engineered soil and cisterns working together. Its reported result—almost 100% of the first two inches of stormwater runoff from the site and building captured, reused and infiltrated on site—was specific to that project’s design and conditions, not a performance guarantee for other properties.
Rank #2
- PERFECT FOR DOWNSPOUTS: Sized specifically to handle residential gutter runoff and garden drainage. Its 15.7" depth allows for easy installation without deep excavation.
- ADVANCED SILT TRAP: Includes a removable filter basket that captures fine debris and sediment, preventing long-term buildup in your underground French drain lines.
- DURABLE COMPOSITE GRATE: The high-strength composite cover is walk-over safe for adults, providing a reliable, rust-proof, and anti-corrosive alternative to metal grates.
- WEATHER-RESISTANT FRP: Crafted from high-strength FRP to withstand shifting soil and extreme temperature changes without warping or degrading like common resin basins.
- VERSATILE ADAPTABILITY: The un-drilled basin walls provide total flexibility. Position your pipe connections at the exact height needed to maintain a proper gravity-fed slope.
Use rainwater where it makes sense
Rainwater harvesting is the practice of intercepting runoff for beneficial use. As Reagan M. Waskom, PhD, of the Colorado Water Institute and Colorado State University’s Water Center, put it: “Rainwater harvesting focuses on intercepting stormwater runoff for beneficial use.”
A simple small-site arrangement can route roof water through gutters and downspouts into sturdy, lidded aboveground containers. Water can also be directed to planted areas designed to receive it. Larger systems may include filters, pumps, underground cisterns, treatment equipment and a separate distribution network for approved nonpotable fixtures.
Design a collection and reuse loop
- Identify roof catchments. Separate clean roof areas from surfaces that may introduce contaminants unsuitable for the intended use.
- Define demand. Match storage to realistic irrigation, toilet-flushing, washing or cooling needs. A tank with no regular demand can remain full when the next storm arrives.
- Provide conveyance. Size and route gutters, downspouts, leaders and underground piping so water reaches storage without eroding soil or flooding entrances.
- Screen and overflow safely. Keep leaves and debris out of the tank, then route excess water to a designed infiltration, detention or drainage feature.
- Protect stored water. Aboveground plastic tanks and decorative wood barrels should have secure lids. Lids reduce evaporation and mosquito breeding, while also limiting debris entry.
- Separate potable systems. Any connection to building plumbing requires approved backflow and cross-connection protection, clear labeling and compliance with the authority having jurisdiction.
- Plan inspection. Include access for cleaning tanks, checking screens, servicing pumps and verifying that overflow paths remain open.
Local rules determine whether rainwater may be collected, how it may be used and what treatment or plumbing safeguards are required. Confirm those rules before installation; the general concepts above are not a substitute for jurisdiction-specific requirements.
Control sediment and pollution during construction
Construction runoff can carry exposed soil, concrete residue, fuel, trash and other pollutants even when the finished site will have excellent controls. Temporary measures must be installed before earth disturbance and maintained as work progresses.
Rank #3
- Fiberglass Reinforced Construction: Made from plastic reinforced with 10% fiberglass to provide added structural strength compared with standard plastic grates. Designed for outdoor drainage systems where durability and stability are important.
- Designed for Standard 6 Inch Drain Pipes: Top diameter 6.75", bottom opening diameter 5.75", and height 2.375". Designed for use with common 6 inch outdoor drainage pipes and drain fittings used in lawns, patios, and landscape drainage systems.
- Helps Keep Leaves and Debris Out: Open grate structure helps prevent leaves, mulch, and debris from entering the drainage pipe while allowing rainwater and surface runoff to pass through for effective yard drainage.
- Suitable for Lawn and Landscape Drainage: Commonly used in small yard drainage systems, landscape drains, patio drains, and garden drainage areas where managing light stormwater runoff is needed.
- Simple Installation: The drain grate installs easily by placing it over the drain pipe or drain fitting. Suitable for DIY yard drainage projects and landscaping installations.
Use a site-specific erosion and sediment plan
- Phase clearing and grading so the smallest practical area is exposed at one time.
- Stabilize completed slopes and disturbed areas as soon as work allows.
- Direct clean water around disturbed ground where feasible, rather than through it.
- Protect inlets, stockpiles and material-storage areas from sediment and spills.
- Provide a designated concrete-washout area and keep waste out of storm drains.
- Inspect controls after storms and repair them before the next rainfall.
Building Design + Construction project descriptions cite silt fencing and a crushed-stone site entrance as examples of construction controls. Treat those as examples, not universal specifications: the required measures, dimensions and inspection schedule depend on the jurisdiction, soil, slope and project disturbance.
Build maintenance into the design
Stormwater infrastructure is an operating asset, not a set-and-forget installation. Assign responsibility, access and budget before turnover. A feature that cannot be inspected or reached with maintenance equipment will eventually lose performance.
Permeable paving
Fine sediment can fill the surface voids and reduce infiltration. Plan routine sweeping and, where needed, vacuuming with equipment appropriate to the pavement system. Keep adjacent soil and mulch from washing onto the surface, and investigate ponding promptly rather than waiting for widespread clogging.
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Plants must tolerate the site’s wetting and drying cycles, salt exposure where applicable and expected maintenance level. Remove invasive growth, replace dead plants, clear sediment from pretreatment areas and keep inlets and outlets visible. A diverse plant palette is beneficial only when grounds staff have the knowledge and time to care for it.
Rank #4
- 【For Dry Well Covers】This 6 inch round surface drain inlet with grate is designed for installation on a compatible dry well cover to create a direct top entry point for surface water runoff. Ideal for yard drainage and underground stormwater drainage systems. Dry well chamber is not included.
- 【Collects Surface Water】This surface drain inlet helps collect surface water from wet spots, low areas, and other places where rainwater tends to build up. A practical add-on for improving yard drainage and moving water into the underground drainage system below.
- 【Grate Helps Block Debris】The drain grate design allows water to flow in from the surface while helping block leaves and other larger debris from entering the opening. Great for everyday outdoor drainage use in yards, lawns, and landscape drainage areas.
- 【Easy to Add】This round surface drain inlet is designed as a practical add-on for a compatible dry well cover. It helps add a direct top water entry point to an existing underground drainage or stormwater drainage setup without replacing the full system.
- 【Package Includes】Includes 1 surface drain inlet with grate. Dry well and other drainage components are sold separately.
Tanks, ponds and underground systems
Inspect lids, screens, pumps, valves, liners, embankments and overflow routes. Keep safety barriers and access controls in place around open water. Record inspections and cleaning so the next facilities team can see what was done and when.
The urban-campus guidance reported by Building Design + Construction highlights these practical risks: permeable pavers can clog without vacuuming, and rain gardens require staff capable of maintaining their plantings. Include those labor and equipment needs in life-cycle comparisons, not only in the construction estimate.
A step-by-step project workflow
- Assemble the baseline. Map roofs, paving, grades, soils, drainage connections, utilities, property lines, receiving waters and existing problem areas.
- Set measurable objectives. Decide whether the priority is volume, quality, reuse, peak-flow control, construction protection or a combination.
- Screen feasible locations. Reserve space for green roofs, swales, rain gardens, ponds, tanks, access lanes and overflow routes before plans are crowded.
- Develop a treatment train. Combine source controls, conveyance, pretreatment, infiltration or storage and safe overflow rather than relying on one device.
- Check soil and structure. Confirm infiltration suitability, groundwater conditions, pavement subgrade behavior, roof loading and underground conflicts through qualified design professionals.
- Coordinate disciplines. Align civil, landscape, architectural, structural, plumbing, electrical and facilities plans so outlets, controls and access are not omitted.
- Verify approvals. Submit the design to the relevant permitting authorities and confirm current stormwater, plumbing, health, fire, accessibility and environmental requirements.
- Plan construction sequencing. Install temporary erosion controls before disturbance, protect completed features from construction sediment and document as-built locations.
- Commission and train. Test pumps, valves, overflow paths and irrigation or plumbing controls; give facilities staff drawings, schedules and inspection checklists.
- Monitor outcomes. Track ponding, sediment accumulation, tank levels, plant condition, pavement infiltration and maintenance events, then adjust the operating plan.
Codes, standards and professional review
Stormwater obligations vary by jurisdiction and can change over time. Confirm current requirements with the authority having jurisdiction rather than relying on a 2015 article or an older project detail. Large or complex sites may require licensed civil, geotechnical, landscape, structural or plumbing professionals, depending on the system.
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Best Value
- DRAIN WATER FROM SURFACE: directly into the Flo-Well Dry Well Kit for detention and infiltration. Works with the Flo-Well Dry Well system to capture and detain excess water and slowly release it into the ground
- EASY TO INSTALL: just knock out the connection hole in the Flo-Well Cover and align the registration tabs at the base of inlet into the cover; also connects to 4 in. Sch. 40 Pipe Fittings directly
- SPECIFICATIONS: 8.2 sq. in. open surface area for 6 in. grate; 25 GPM flow rate; Rated for NDS Class A loads (up to 60 psi) when properly installed—recommended for pedestrians, bicycles, wheelchair traffic, and lawn tractors; ADA compliant
- PREVENT WATER DAMAGE: Eliminates traditional drainage problems such as standing water in yards. Drain grate prevents debris from entering the Flo-Well dry well. The Flo-Well dry well size and gravel-free interior provide 2 ½ times water holding capacity than comparable sized gravel-filled dry wells.
- INCLUDES: Comes with 1 Surface Drain Inlet with 6 in. Drain Grate; Inlet grate is 6 in. diameter, 9 in. total inlet height; The Flo-Well Stormwater Dry Well System is sold separately
Common failure modes and corrective actions
| Symptom | Likely cause | First response |
|---|---|---|
| Water ponds on permeable pavement | Surface clogging, sediment from adjacent areas or blocked underdrain | Inspect inlets and outlets, remove sediment and arrange appropriate sweeping or vacuuming; investigate the subgrade if ponding persists |
| Rain garden remains saturated or dies out | Inadequate soil conditions, blocked outlet or plants mismatched to hydrology | Check grades, underdrain or overflow, remove accumulated sediment and revise the plant palette with qualified guidance |
| Tank overflows during ordinary storms | Storage is undersized, demand is lower than expected or reuse equipment is offline | Verify demand, controls and overflow routing; do not bypass required safety or plumbing protections |
| Sediment leaves the construction site | Controls were installed late, damaged or overwhelmed | Stabilize exposed soil, repair perimeter and inlet controls, clean tracked sediment and increase post-storm inspections |
| Neighboring property receives concentrated flow | Grades or downspouts changed without a complete flow-path review | Trace the discharge, provide lawful conveyance or storage and coordinate corrective work with the design team and jurisdiction |
How to choose among options
Choose the smallest combination of measures that can meet the project objectives while remaining maintainable. A constrained urban redevelopment may favor roof capture, permeable walkways and underground storage. A campus or industrial site with open land may have room for bioswales, rain gardens or a pond. A building with a reliable irrigation demand can justify cistern capacity that would be uneconomic where water use is seasonal or minimal.
Document why each measure was selected, what it is expected to do, who will maintain it and what happens when it is full, clogged or offline. That record lets owners compare proposals on whole-life performance instead of initial cost alone.
What current runoff figures do—and do not—tell you
Building Design + Construction reported an average of 59.5 million acre-feet of stormwater runoff per year, described in the same report as 53 billion gallons per day. That figure is attributed to the March 18, 2024 publication and should be treated as a reported national-scale estimate from that secondary source, not as a design value for an individual property. Project sizing still requires local rainfall, catchment area, soils, storage and discharge criteria.
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