How to care for a rain garden or other stormwater facility on your property

Photo shows a rain garden with basin of rocks and good plants coverage.
Thank you for managing the rain on your property! Follow these important steps to make sure your rain garden, basin, planter, swale, disconnected downspouts, or other stormwater management facility keeps working safely and as designed.
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Rain gardens, basins, planters, swales, disconnected downspouts, and other stormwater solutions require regular maintenance to keep them safe and fully functioning. In addition, if you receive a Clean River Rewards discount for stormwater services, maintenance is required in order to keep the discount.

Do you have a required maintenance plan?

Properties with operations and maintenance (O&M) plans are required to follow the maintenance schedule and activities outlined in that plan. You may have a required O&M plan for your home or property if it:

  • Was built or substantially renovated or expanded after 2001, when Portland started requiring onsite stormwater management for new construction. These properties may have an O&M plan recorded to the property’s deed on file with the County.
  • Participated in the Environmental Services’ rain garden program (also called the Private Property Retrofit Program). Properties participating in this program have signed maintenance agreements on file with the Bureau of Environmental Services. If your facility was installed through this program, contact Environmental Services Private Property Drainage Inquiries.

If you’re not sure, contact the Environmental Services Maintenance Inspection Program (contact information on this page) to request help locating your facility/facilities and the required O&M plan.

Do you have disconnected downspouts?

If your property participated in the Environmental Services Downspout Disconnection Program, you don’t have a signed O&M agreement. However, maintaining your disconnected downspouts is still required. See below for required maintenance activities. Contact Environmental Services Private Property Drainage Inquiries with questions.

Do I need a permit?

Most maintenance and repairs within a rain garden or vegetated stormwater management facility can be completed without permits. However, changes or replacement of drainage features such as downspouts, catch basins, or stormwater piping will generally require a plumbing trade permit. If you or your contractor is unsure of permitting for repairs or replacement, schedule a free 15-minute permit consultation.

Safety first! Prevent damage to buildings and property.

It’s very important to manage stormwater on your property safely so that it does not damage buildings, property, or neighboring properties. Not all properties are the same, and not all stormwater management is the same. It’s important to select the proper management solutions for your property. For questions or onsite guidance, request technical assistance for drainage issues on your property.

Prevent moisture or standing water.

Moisture or standing water in or near your house poses the greatest risk of property damage. Water can leak into the basement or crawl space or cause erosion around foundations. Improperly directed water can damage your or your neighbors’ property or structures. Check to make sure:

  • Your facilities collect and direct stormwater runoff away from any building foundation.
  • There is no spillover near a foundation from a clogged gutter, downspout, or rain drain. A rain drain refers to the pipes that connect downspouts to stormwater facilities.
  • Infiltration facilities have certain required setbacks from foundations and property lines. Please refer to section 2.2.4 of the Stormwater Management Manual regarding setbacks. 

Basic routine maintenance

For all facilities with plants, please follow this general information to maintain your facility to keep it looking good and functioning well.


Photo shows basin of rain garden filled with gray silt and debris.
Sediment builds up in a rain garden, blocking flow and harming plants.
  • Remove trash, dead leaves, and debris.
  • Check inlets for erosion and clear them of sediment and obstructions.
  • Check that splashblocks or rocks are in place under inlets.
  • Clean gutters and clear downspouts. For best results, be sure to do this regularly throughout the fall and winter.
  • Pull weeds. Need help with identification? Check out the weed identification guide we created for our Green Street Stewards. It covers the most commonly found weeds.

At least once every year

Photo shows grasses in a rain garden trimmed to about 6 inches tall.
Trim grasses no shorter than 6 inches.
  • Replace dead or missing plants — best done in spring and fall when new plants can get a better start.
  • Prune trees and shrubs. This is best done during fall or spring. Find pruning tips from Portland’s Urban Forestry.
  • Leave sedges and rushes. If you need to prune them, don't trim them any shorter than 6 inches in height. Remove dead material through cutting or raking. 
  • Divide and move plants around the facility as needed. Plants should cover 90% of the space. 
  • Clear plants from inlets and outlets by a 1-foot radius.

Special summer activities

During the hot, dry summer months (May through October), water plants weekly or daily depending on temperature and sun exposure. Irrigation systems can be a good solution for full sun or especially high-heat conditions. 

Common problems and their solutions

What should I do about ponding water? Is it a problem?

Stormwater facilities are designed to hold water during and after a rain. Ponding water in the facility doesn’t necessarily indicate a problem. Most will drain within 48 hours after the rain has fully stopped. If you notice standing water in your facility longer than 48 hours after the rain has stopped, then contact the Environmental Services Private Property Drainage Inquiries.

The inlets are blocked

Shows photos side-by-side of a black pipe opening situated between rocks. In one, the pipe is full of dirt and debris. In the other, the pipe is open.

Blocked inlets are a very common problem and a critical one to resolve. If water cannot access the facility, then it can back up onto your property and cause damage. Take these steps:

  • The most common cause of a blocked inlet is debris build-up coming from gutters. The best way to avoid inlet obstruction is to regularly clear your gutters and check that the inlets of your rain garden are clear at least twice each year. 
  • If you do experience a blocked inlet, first check inlet openings in your facility and clear them by hand, if possible. 
  • If the blockage cannot be reached by hand, try to use a high-pressure nozzle on a hose to send a jet of water down the standpipe, where it connects to your downspout to loosen debris. 
  • If the inlet pipe of your rain garden is buried in soil or debris and is not visible, try to send water into the pipe at the downspout connection. Watch for where water seeps out. This can reveal a hidden or buried inlet. 
Photo shows hand with wad of roots pulled from inside a pipe.
Pull out any root wads blocking inlets.
  • Another common cause of inlet blockage is root growth into the inlet pipe. Remove these by pulling on the roots from the open end of the inlet pipe. To avoid this problem, remove all plants in a 1-foot radius around an inlet as part of regular maintenance at least twice a year. 

Debris is killing the plants.

Photo shows rain garden completely covered by leaves.
Debris build-up is smothering plants. Rake and remove leaves regularly to prevent build-up.

Healthy, established plants aerate the soil and allow for better infiltration while providing habitat for pollinators and wildlife. Natural debris, especially leaves, can collect, fill facilities, and smother plants. Leaf debris builds up over time and eventually creates soil which can reduce infiltration and lead to capacity and ponding issues. To solve:

  • Rake up leaves and remove debris regularly, especially in the fall and early winter.
  • Remove dead or dried plant material.
  • Sedges and rushes can be divided and removed to contain spread, if needed.
  • Prune plants.

Don’t block the escape route.

Photo shows a small green drain at the bottom of a basin with rocks and plants
Keep overflow drains clear.

Every system needs a safe overflow plan for those times when it rains a lot or for a long time. Know what the overflow plan is for your facility and maintain it.

  • Ensure the escape route is the lowest point around the border of the rain garden. 
  • Keep the escape route clear of debris, soil, and plants that could get in the way of water flowing out of the facility should it reach its capacity. 
  • Make sure the escape routes direct overflow away from structures.
  • In facilities with overflow pipes or grates, remove any debris or obstructions to the overflows or grates so stormwater can properly drain.

Watch for erosion or soil settlement.

Erosion typically occurs below piped inlets or downspouts to a facility. Settling happens when a boulder or side slope moves into a different position than originally constructed. Settling is not always a major problem. However, it is important to note any change in the structure of your facility. To resolve erosion or settlement issues: 

Photo shows the end of a black pipe located between rocks with water flowing out of it.
Placing splashblocks or drain rock below inlets can help prevent erosion.
  • Place splashblocks or drain rocks below inlets to prevent erosion.
  • Backfill eroded areas with soil and protect them with splashblocks or rocks.
  • Add groundcover plants, gravel, or river rock. Reset the boulder or reshape the side slopes.
  • Contact Environmental Services Private Property Drainage Inquiries if you notice repeated erosion or settling.

How to maintain your disconnected downspouts

Many systems include disconnected downspouts that direct water to a landscaped area. Follow these steps to keep them working.

Keep your gutters clean and in good repair.

  • Clean gutters at least twice a year and more often if you have trees. 
  • Check that gutters are tilted to direct water to downspouts. 
  • Make sure all parts are screwed together. Caulk leaks and holes. 
  • Make sure roof flashing directs water into the gutter.
  • Look for low spots or sagging areas along the gutter line and repair with spikes or place new hangers as needed.

Keep your downspouts in good repair. 

  • Check and clear elbows or bends in the downspouts to prevent clogging. Each elbow or section of the downspout should funnel into the one below it. All parts need to be securely fastened together. 
  • Avoid removing or redirecting extensions.
  • If your downspouts are disconnected at the surface:
    • Make sure water drains at least 2 feet away from crawl spaces, porch steps, garages, or walkways and at least 6 feet from a basement, retaining wall, or oil tank.
    • Water should drain at least 5 feet from the property line. 
    • The extension, splashblock, and ground – all should drain water away from structures.
    • Always use a splashblock to absorb the energy of falling water and prevent erosion.
  • If your downspout connects to an underground pipe:
    • Inspect standpipes regularly for clogs.
    • Check to ensure standpipes aren’t loose below the surface or cracked. 
  • Don’t reconnect your downspouts. If you experience drainage problems, request technical assistance for drainage issues on your property.

Pay attention to the landscaping.

  • The ground should slope away from structures.
  • Don’t build up soil, bark dust, or woodpiles against the foundation or siding.
  • Don’t overwater. Use vegetation that requires less water and absorbs runoff.
  • Avoid draining water onto impermeable plastic weed barrier fabric.
  • Driveways and patios should be free of cracks and sloped away from foundations. You may need to seal the seam between the foundation and the pavement. 

How to maintain structural and manufactured stormwater treatment technologies

Many properties in Portland also have structural or manufactured stormwater treatment technologies. Examples include sedimentation manholes and StormFilter catch basins and vaults. It is highly recommended to hire a licensed contractor for maintenance on these types of facilities.


Private Property Drainage Inquiries

Environmental Services
phone number503-823-5858For questions from home and business owners about safe ways to manage the rain on their property or solutions to drainage problems.

Stormwater Maintenance Inspection Program

Environmental Services
phone number503-823-5313For assistance with researching required O&M plans, identification of existing facility locations, and maintenance of stormwater management facilities like rain gardens, planters, and swales on private property.