Awaiting expert review. This page covers safety or regulatory rules that change over time. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
Stormwater runoff management is the set of practices, from rain gardens and downspout disconnection to city storm sewer programs, that slow rain, let it soak in near where it falls and keep pollutants from washing into streets, storm drains and waterways.
EPA calls the home-scale version low impact development or green infrastructure. It works with nature to manage stormwater as close to its source as possible. Rules come from your city or county, so the same yard can face different requirements in different places.
Quick facts
The key facts about Stormwater Runoff Management, with sources:
- Core problem
- Hard surfaces and compacted land block soak-in, which raises the volume and speed of runoff 1
- Home-scale tools
- Rain gardens, rain barrels, permeable pavement, bioretention and green roofs, per EPA 12
- Rain garden
- A depressed area that collects water from a roof, driveway or street and lets it soak into the ground 3
- Who is regulated
- Operators of municipal separate storm sewer systems (MS4s), not individual homeowners, under EPA’s permit program 4
- Phase I and II
- About 855 Phase I MS4s and 6,695 Phase II MS4s are named on EPA’s page 4
- Dry wells
- EPA treats stormwater infiltration systems with added piping as Class V injection wells under the UIC program 5
- Before digging
- EPA advises accurate information about underground utilities before you dig a rain garden 3
Key takeaways
- Stormwater management is about where rain goes and what it carries. On a yard, that means slowing it, soaking it in and keeping it clean.
- EPA names rain gardens, rain barrels, permeable pavement and bioretention among the practices that handle runoff near its source 1.
- Cities and counties, not homeowners, hold the federal stormwater permits. Your local program sets what applies to your yard 4.
- Never send runoff to a neighbor or the sanitary sewer. Ask your stormwater office before you change a drain, outlet or large grade.
- Some systems, such as dry wells, can fall under federal underground injection rules. Check before building one 5.
What stormwater is, and why it needs managing
Stormwater is rain and melted snow that runs off roofs, driveways, lawns and streets instead of soaking in. In natural ground, most of it soaks in.
In built areas, much of the land is covered by buildings, pavement and compacted landscape.
EPA says these surfaces do not let rain and snowmelt soak into the ground, which greatly increases the volume and speed of stormwater runoff 1.
That runoff picks things up. EPA lists sediment, oil and grease from vehicles, pesticides and nutrients from lawns and gardens, bacteria from pet waste and failing septic systems, road salt and heavy metals 1. It carries them into storm drains and streams.
Management is the response. EPA describes low impact development, also called green infrastructure, as an approach that uses natural processes to infiltrate, evaporate or reuse stormwater, working with nature to manage it as close to its source as possible 1.
Its list of practices includes bioretention facilities, rain gardens, vegetated roofs, rain barrels and permeable pavement 1.
On a home lot, that comes down to a few choices: where the roof water goes, how the lawn and soil take in water, and whether you add a planted basin or a barrel. The other pages in this glossary cover the pieces. This page owns the big picture and the rules.
How a yard can slow and clean runoff, step by step
Think of it as a chain from the roof to the street. Each link keeps more water on the lot.
- Catch it at the roof. Gutters and downspouts collect the roof’s water. Where it ends is the first choice 7.
- Spread it out. A downspout extension, splash block or swale slows the flow and gives it a path 710.
- Let it soak in. Planted ground, a rain garden or permeable surfaces let water enter the soil instead of the street 31.
- Loosen packed soil. The Susquehanna River Basin Commission says compacted soil prevents rainwater from soaking in and can be improved with a core aerator or compost 9.
- Keep pollutants off the surface. Fertilizer, pesticide and pet waste on hard surfaces wash off in rain 19.
- Send only the overflow away. What cannot soak in should leave by an outlet that the city allows.
- Roof and guttersCollect rain at the source
- Downspout endExtension, splash block or barrel
- Soak-in zoneLawn, swale, rain garden
- Overflow pathSafe, legal outlet
- Street or storm drainThe public system; city rules apply
The chain follows EPA’s source-control approach and the City of Portland downspout guide. Source: [1] [7]
Home-scale stormwater practices
| Practice | What it does | Typical place | What the sources say |
|---|---|---|---|
| Downspout disconnection | Sends roof water to planted ground | Roof edge | Portland describes cutting, plugging and extending 7. See downspout drainage |
| Rain garden | A planted basin that holds runoff so it soaks in | Low area that receives roof or driveway water | EPA: a depressed area that collects water from a roof, driveway or street 3 |
| Rain barrel | Stores roof water for later use | Beside a downspout | EPA lists rain barrels among practices; check state rules 16 |
| Permeable pavement | Lets water pass through the surface | Patios, drives, paths | EPA names permeable pavements 1. See permeable pavers |
| Swale | Carries and slows runoff on the surface | Along lot edges or slopes | PNNL: slows, filters and soaks in runoff 10. See swale vs. berm |
| Mini-wetland | Turns a wet low spot into planted habitat | A swale or heavy clay low area | SRBC says it can store, filter and clean roof and lawn runoff 9 |
Example: following one roof’s water through the chain
The lot below is invented. The roof size is an example, and the planted-ground figure uses Portland’s local 10 percent sizing factor 7. Your city may use a different method.
| Step (example lot) | Choice | Check from the sources | Result |
|---|---|---|---|
| Roof on one downspout | 600 sq ft | Portland: planted ground at least 10 percent of roof area 7 | 60 sq ft of ground needed (our arithmetic) |
| Where it ends today | Piped into the sanitary line | Jefferson County lists this as incorrect roof drainage 8 | Ask the utility before disconnecting |
| Soak-in zone | Lawn bed 6 ft by 10 ft | 60 sq ft; check slope and hazards 7 | Meets the local factor on paper |
| Soil | Packed from construction | SRBC: compaction blocks soak-in 9 | Loosen soil or add compost first |
| Overflow | Swale to the lot’s low corner | Outlet must not harm a neighbor 11 | Confirm with the stormwater office |
Yards rarely check every box. The point is the order: roof, spread, soak, overflow. If the soak-in zone is too small, a rain garden or a dry well may be the next option. A pro should size either one.
Where homeowners meet stormwater rules
On a utility bill. Some cities charge a stormwater fee and give credits for keeping rain on site. Portland offers a discount on the stormwater part of the city utility bill for containing rain 7. Other places have no such program.
In a permit. A new patio, a large grade change or a drain tie-in can need approval. The city’s stormwater program sets the details.
In an HOA or builder plan. Developments may include basins or swales you are not allowed to alter.
In a landscape plan. Designers use green infrastructure terms for rain gardens and permeable surfaces. See landscape design and drainage and grading.
In a lawn program. Fertilizer and pesticide use affects what runoff carries. EPA lists lawn and garden pesticides and nutrients among urban runoff pollutants 1. Our lawn chemical safety page covers label basics.
What managing runoff on site can do, and what it cannot
What it can do
- It reduces the volume of runoff that reaches streams and keeps pollutants out of waterways 9.
- Disconnected downspouts can keep water out of the sewer; Jefferson County says a 1,500 square foot home can redirect 25,000 gallons a year 8.
- It can cut basement flooding from sanitary sewer backups 8.
- Planted systems filter runoff and support wildlife, as SRBC notes for mini-wetlands 9.
Limits and trade-offs
- It needs soil that can take in water. Compaction, clay or a high water table limit soak-in 913.
- Some systems are regulated, such as dry wells with added piping 5.
- Space is a limit. Portland’s guide needs planted ground equal to 10 percent of the roof area 7.
- Poor design can move water to a neighbor or the foundation 1110.
What the sources do not cover
EPA’s pages describe practices and programs. They give no yard-scale sizing rules, and EPA’s rain garden page gives no dimensions or depth 3. We do not give any either. A designer or your city’s manual should set the size for your soil.
EPA’s MS4 page explains who holds permits, not what a homeowner must do. It says the obligations fall on the regulated operators, and resident-level rules depend on the local program 4. We found no single national homeowner rule.
Portland, Jefferson County and the Susquehanna River Basin Commission are local or regional sources. Their distances and factors do not apply everywhere.
This page is held for review. It has not been signed by a licensed civil engineer, landscape architect or stormwater professional, and it should not be used to design a system.
What drives the cost, and how long systems last
We publish no prices. For a yard, cost moves with the size of the roof area, the soak-in area you need, the soil, the excavation, plants, pipe, rock and how far water must travel. A disconnection with an extension is a small job. A rain garden, a buried line or a dry well is larger.
City programs can change the math. Portland gives a utility discount for containing rain on a property 7. Check whether your city has a credit, a rebate or a design guide before you pay for a system.
No source gives a service life for these practices. Clogging, plant health and maintenance decide it, so we give no number. See the cost guide and the landscaping cost estimator for what sets a bid.
Who plans and builds, and how a project runs
A homeowner can disconnect a downspout or add a barrel. A rain garden, a swale or a dry well is usually a job for a landscape or drainage contractor, with design help for anything near a building.
- Find your local stormwater or public works office and ask what applies to your lot.
- Map the roofs, paved areas and where water goes today.
- Check the soil. The NRCS Web Soil Survey maps mapped soils at your address 14, and a hole test shows local drainage.
- Call 811 before digging. EPA says a rain garden needs accurate utility information before you dig 3.
- Pick the practice and a safe overflow path. Ask whether a permit or an inspection applies.
- Build, plant and protect the outlet from erosion.
- Watch it through the first big rain and adjust.
No runoff onto neighbors or into the sanitary sewer
Keep runoff on your own lot or send it only to an outlet your city allows. Michigan State University Extension warns that redirecting runoff can harm neighboring properties 11.
Do not connect roof or yard drains to the sanitary sewer; the City of Homer, Alaska, calls such connections prohibited 12. Do not build a rain garden or drain over a septic field, or near a foundation, without a pro. Call 811 first.
Keeping a runoff system working
Upkeep tasks are listed here without fixed dates.
- Clean gutters and clear downspouts. Portland says at least twice a year, and more with overhanging trees 7.
- Check outlets for erosion. PNNL suggests splash blocks or stones at outlets 10.
- Keep soil from compacting. SRBC says core aeration or compost can improve compacted soil 9.
- Keep debris out of swales. PNNL notes organic debris can fill a swale 10.
- Watch pollutants. Sweep fertilizer and clippings off hard surfaces so rain does not wash them away 1.
- Look after the plants. A planted basin works only if the plants are healthy.
Warning signs, and when to call a pro
- Water at the foundation or in the basement. PNNL links saturated foundations to mold and poor indoor air quality 10.
- Erosion or gullies where water leaves. EPA ties runoff to higher volume and speed 1.
- A basin that stays full for days. The soil may be too slow; see yard ponding.
- A neighbor’s complaint. Stop and review the outlet.
- A roof drain tied to the sanitary line. Jefferson County lists this as incorrect 8.
Call a civil engineer, landscape architect or drainage contractor for anything near a foundation, on a steep lot, or involving an underground system. Our guide to choosing a landscaping company covers what to ask.
Federal, state and local rules, kept apart
Federal permit program, for cities. EPA’s stormwater program regulates municipal separate storm sewer systems (MS4s), which are public systems that collect stormwater and discharge to waters of the United States.
The Phase I rule from 1990 covers medium and large cities and certain counties with 100,000 people or more, and the Phase II rule from 1999 covers small MS4s in urbanized areas 4.
Regulated operators write a stormwater management program that describes the practices they will use 4. This is a permit duty on the operator, not on a homeowner.
Federal rule for injection wells. Under the Safe Drinking Water Act, EPA sets minimum standards for Class V underground injection wells, and stormwater infiltration systems with added piping meet the definition.
They are authorized by rule when they do not endanger drinking water and the owner submits basic inventory information. Some states run their own programs, and their rules may be stricter 5.
EPA’s page does not state a residential exemption, so ask your state or EPA region before building a dry well.
Local rules. Cities and counties set outlet rules, permits, setbacks and credits. PNNL tells readers to follow local stormwater ordinances 10.
Product labels. Fertilizer and pesticide labels are separate from stormwater rules and apply to anything you spread on a lawn.
Stormwater management vs. related terms
| Term | What it is | How it differs | Read more |
|---|---|---|---|
| Stormwater runoff management | The whole system of practices and rules | Covers yard, street and city scales | This page |
| Yard drainage | Moving water out of a lot | A narrower goal: get rid of water | Drainage and grading service |
| Erosion control | Keeping soil in place | One result of good runoff control | Erosion control in yards |
| Soil drainage and infiltration | How soil takes in water | Sets how much soaks in | Soil drainage and infiltration |
| Hardscape drainage | Water on patios and paths | A source of runoff | Hardscape drainage |
Common myths about stormwater
- Myth Stormwater goes to a treatment plant.
- Reality In many places it flows through storm drains to streams without treatment. EPA says polluted runoff is commonly carried by municipal separate storm sewer systems and often discharged untreated 4.
- Myth It is only a city problem.
- Reality EPA’s program puts permits on cities, but runoff starts on private roofs, driveways and lawns 19.
- Myth A rain garden is a place to dump water.
- Reality EPA describes it as a planted area that lets runoff soak in, and says to check utilities before you dig 3. It still needs a safe overflow.
- Myth Disconnecting a downspout is always allowed.
- Reality Portland says not to disconnect on slopes over 10 percent or near certain hazards 7.
- Myth Rain barrels are legal everywhere.
- Reality EPA’s watering tips say some states restrict rainwater collection, so check first 6.
The regional variable: your city’s stormwater program
The variable here is local rule, not climate alone. Whether you sit inside a Phase I or Phase II MS4, what your city allows at the curb, and whether a credit or a manual exists all depend on where you live 4.
Portland, Oregon, ties a utility discount to keeping rain on a property 7; most cities do not. Soil and rainfall matter too, and the NRCS Web Soil Survey maps your soil 14.
Find your city or county stormwater office, and read our research page for how soil drainage varies by region.
When this matters, and your next step
The work matters when you plan a new hard surface, a big regrade, a drain or a rain garden, and when water leaves your lot in a way that could affect a neighbor or the street. It also matters when your roof drains into a sewer.
Your next step is small. Call or visit your city’s stormwater page and ask three things: what rules apply to my lot, are downspouts allowed to discharge on the surface, and is there a credit or guide for rain gardens.
Then pick the lowest-effort step that works: disconnect a downspout, loosen packed soil, or add a planted basin. Bring a pro in for the rest.
Start at the roof
Roof water is the part of runoff you control most easily. Fix where the downspouts end before you plan a rain garden or a drain.
Questions about Stormwater Runoff Management
What is stormwater runoff management?
It is the set of practices and rules that slow rain, soak it in close to where it falls and keep pollutants out of streams. EPA calls the yard-scale version low impact development or green infrastructure, and says it works with nature to manage stormwater as close to its source as possible.
What is a rain garden?
EPA describes a rain garden as a depressed area in the landscape that collects rain water from a roof, driveway or street and lets it soak into the ground. It is planted with grasses and flowering plants. It needs the right soil, a safe overflow and a utility check before anyone digs.
Do homeowners need a permit for stormwater practices?
It depends on your city and the work. EPA’s federal permit program applies to cities that run storm sewers, not individual homeowners. Local rules can still require approval for large grading, drains, new hard surfaces or tie-ins. Ask your local stormwater or building office before you start.
What is an MS4?
It is a municipal separate storm sewer system, owned by a city, town or other public entity, designed to collect stormwater and discharge it to waters of the United States. EPA regulates these systems under a permit program, and the operator writes a stormwater management program. It is not a combined sewer.
Can I connect my downspout to the sewer?
In many places you cannot. Jefferson County, Missouri, lists downspouts draining into the sanitary sewer as incorrect, and the City of Homer, Alaska, calls roof drain connections to the sanitary sewer prohibited. Ask your utility before changing any pipe.
Is a dry well regulated?
It can be. EPA says stormwater infiltration systems with added piping to enhance infiltration meet the definition of a Class V injection well under its Underground Injection Control program. They are authorized by rule when they do not endanger drinking water and the owner submits basic information. Some states have stricter rules.
How much ground does a downspout need to soak in?
The City of Portland says the planted ground should be at least 10 percent of the roof area that drains to the downspout, so 500 square feet of roof needs 50 square feet. That is a local rule of thumb. Soil, slope and rainfall can change the answer where you live.
How do I reduce runoff from my yard?
Start with roof water, then loosen packed soil and keep chemicals off hard surfaces. The Susquehanna River Basin Commission suggests disconnecting downspouts, adding rain gardens, reducing paved area and improving compacted soil with a core aerator or compost. Follow local rules on where water may go.
What pollutants does stormwater carry?
EPA lists sediment, oil and grease from vehicles, pesticides and nutrients from lawns and gardens, bacteria and viruses from pet waste and failing septic systems, road salts and heavy metals. These wash off hard surfaces into storm drains and streams. Keeping them off driveways and sidewalks helps.
Are rain barrels allowed everywhere?
No. EPA’s watering tips say rain barrels and cisterns can supplement irrigation but that some states restrict rainwater collection, so check with your state’s water resource agency first. A barrel also needs an overflow that sends extra water away from the house.
Sources
- U.S. EPA, Nonpoint Source: Urban Areas (updated July 21, 2026), retrieved .
- U.S. EPA, Green Infrastructure (updated July 27, 2026), retrieved .
- U.S. EPA, Soak Up the Rain: Rain Gardens (archived program page), retrieved .
- U.S. EPA, Stormwater Discharges from Municipal Sources (updated May 20, 2026), retrieved .
- U.S. EPA, Stormwater Drainage Wells, Underground Injection Control (updated January 20, 2026), retrieved .
- U.S. EPA WaterSense, Watering Tips (updated March 11, 2026), retrieved .
- City of Portland Environmental Services, How to Manage Stormwater: Downspout Disconnection (ES1919, updated February 2020), hosted by the University of New Mexico Southwest Environmental Finance Center, retrieved .
- Jefferson County (Missouri) Stormwater Division, Managing Gutter Runoff, retrieved .
- Susquehanna River Basin Commission, Homeowner Stormwater Practices pamphlet, retrieved .
- Pacific Northwest National Laboratory, Building America Solution Center, Swales, Drains, and Site Grading for Stormwater Control (updated 2020-09-27), retrieved .
- Michigan State University Extension via Ask Extension, answer on a wet yard and drainage options, retrieved .
- City of Homer, Alaska, Public Works, Illegal connections to the sanitary sewer system, retrieved .
- Cornell University, Northeast Region Certified Crop Adviser Study Resources, Surface and Subsurface Drainage, retrieved .
- USDA NRCS, Web Soil Survey, retrieved .
Expert review
Written by the HyreYard Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Held for G-REV. EPA program facts (runoff mechanism, practices, MS4 definitions and counts, Class V stormwater wells) were read on epa.gov pages; no CFR section was loaded, so none is quoted.
EPA’s rain garden page is marked as no longer updated. Local figures come from Portland, Jefferson County (Missouri), the Susquehanna River Basin Commission and the City of Homer, and are labelled as local.
The SRBC PDF text was extracted from the downloaded file. The example lot is invented. We give no sizing rule, price or lifespan. No qualified reviewer has signed this page.
Suggest a correction. We fix errors and say what changed.