This is where I should have consulted an engineer. I am not sure this is the best way to connect the two downspouts that empty into the trench. The other way would have been to bring a second trench along the top of the slope and then down to the rain garden.
Here the plastic lined pea gravel filled trench flows into the deep section of the rain garden.
The trench to the rain garden is lined with plastic held in place with pins I made from old shirt hangers and a wire cutter. Then we filled in with bags of pea gravel. It took about ten bags fron Menards. I may add some larger rocks later to give it a stream-like look. I think a few flat rocks under the gutter pipes at both locations instead of just sitting on the gravel for sure. When it rains the water does not show in the trench but if you stick your fingers in you can feel the water moving through when it rains. It is working very well so far.I find myself out in the rain watching to be sure.
The rain garden is not actually a water garden. It is a large level hole we dug two spades deep along but slightly lower than the sidewalk and a slope that edges the garden. It is refilled with compost mixed with part of the soil dug out to make a very well drained space that can hold the runoff rain from the roof of the buildings and/or sidewalks and other higher areas to give the water time to be drawn deep into the soil rather than into sewers. Established plants rarely need to be watered.Newly planted material always needs watering for awhile, maybe the entire first summer if it is hot and dry. If you use native plants with deep roots it takes a couple of years to grow those very deep roots but then you may never have to water the rain garden again.
The longest water has sat on the surface of the rain garden has been a couple of hours. If the rain garden fills during a very long heavy rain(like once it rained in a heavy downpour for 45 minutes) excess rain will then follow the natural path of run-off to the sewers in the alley. No danger to house. No mosquitoes.
It was hard work digging the hole so if you try it make sure you have help or take it real slow.
Some of the annual coreopsis is beginning to bloom and soon the purple coneflower will follow. Liatris has loads of flower buds but it will be a couple of weeks.
What I think is trifolium rubens will soon bloom for the first time for me in the garden. The rabbits have not eaten this one and only specimen.
I divided several large clumps of panicum and spread throughout the rain garden so it will be next year before it comes into its prime.
I have not added Ratibida pinnata /yellow coneflower or aster but there is plenty nearby.First some of the other plants need a chance to grow so as to be able to compete for space.
Many flowering plants and grass are very small yet as I started them from seed in a winter sowing project.
Only one compass seed germinated and it is still in a container where I can protect it for awhile.
This is a fun project...
Rain Gardens . org
dnr wi gov
rain gardens network
A picture of Silphium Compass Plant