Solving Typical Rain Garden Problems
Many of us embraced rain gardens in the past several years for their ability to mitigate storm water runoff and to help cleanse groundwater of pollutants.
We love rain gardens; we really do. It’s just that sometimes rain gardens don’t love us back. Here are some reasons that rain gardens don’t always work, and the most likely solutions:
1. Problem: Lack of an underdrain. Rain gardens are designed to infiltrate storm water into the soil. But sometimes they fill up faster than they can drain.
Solution: Install a 4’’ perforated pipe underdrain below the rain garden basin. This underdrain operates as a kind of relief valve if excess water accumulates in the rain garden. The underdrain is connected to an outlet structure, which is there to function during intense storm events when the basin fills up.
2. Problem: Clay and silt clog the perforations in the 4” underdrain pipe.
Solution: If the rain garden stops draining, the underdrain pipe may be clogged. Flush the underdrain pipe with a garden hose via the outlet structure.
3. Problem: Sediment washes into the rain garden from surrounding surfaces, filling in all the desirable and needed air pockets in the mulch, preventing infiltration.
Solution: Protect the rain garden from sedimentation with a silt fence or filter sock until the surrounding areas are stabilized with vegetation or paving.
4. Problem: Water won’t seep into the soil. Sometimes heavy construction vehicles compress subgrade soil to a degree that water cannot infiltrate.
Solution: Loosen the subgrade before constructing the rain garden.
In Pittsburgh, Green is in the Air
It’s summer and that means the City is green with trees. Not only are plants in the midst of their growing season, but people are in the midst of launching green initiatives. Last week we attended a poster session during the Who’s Who in Green Infrastructure Implementation event hosted by the Green Building Alliance and organized by 3 Rivers Wet Weather. The event was packed with people interested in sharing their projects and learning more about green infrastructure.
This morning over 80 people packed a Pittsburgh Zoo conference room to kick-off this year’s Green Workplace Challenge (GWC), a program of Sustainable Pittsburgh. We took part last year in the challenge and are excited to enter again this year with the revamped program.
Promoting Green Infrastructure
Sometimes it’s hard to convince people that more trees are good or that the extra cost for installing pervious paving can go a long way later. The good news is that the Federal, State, and local governments are starting to recognize the importance of green infrastructure in protecting our health, safety, and welfare in addition to future cost savings and improving the environment.
Rain Garden Myths
When people first learn about the term “rain garden”, they often have pre-conceived notions about them. For example, some people begin visualizing a big hole in the ground that fills up with water and can be dangerous for kids. We would like to clear the air about the following myths:
Rain Gardens are More Maintenance
Rain gardens require no more maintenance than your typical planting bed. In fact, many common plants that are used around your home can be used in rain gardens. Using native plants will reduce the amount of maintenance compared to non-natives. It all depends on the types of plants you specify.
Rain Gardens Create More Flooding
My neighbor asked me once about whether the rain garden I installed in my own backyard would create more flooding in his yard and basement. I quickly reassured him that unless I secretly piped my overflow into his yard, he would not have any flooding because of my rain garden. A good overflow plan is important for preventing extra water from going where you don’t want it to go.
Rain Gardens Harbor Mosquitoes
Rain gardens are designed to hold water for up to 48 hours, which is not long enough for mosquitoes to breed.
Rain Gardens are Detention Basins, Ponds, or Wetlands
Rain gardens are none of the above. They are similar in that they help store stormwater runoff. However, they are dry most of the time and are not as deep as detention basins.
Rain Gardens Create a Liability
We’ve run into clients that do not want rain gardens because they believe they are a liability. “Some kid is going to fall in and drown in a few inches of water that may accumulate during a storm event”. Well, we strongly believe the benefits far outweigh the risk. In fact, numerous schools around the country have promoted and used rain gardens as educational tools. Below are just a few examples of rain gardens planted in public spaces or on school properties:
- NE Siskiyou Street – Portland, Oregon (photo by Kevin Robert Perry)