To be perfectly clear, I am not saying you cannot or should not drain your roof water into your pervious concrete stormwater management system. I am saying there is a right way and a wrong way to do it. The picture below is a great example of what happens when done the wrong way.
Directing roof water, and the fine sediment it contains, directly onto the surface of the pervious concrete pavement is a guaranteed way to cause localized clogging. Regular maintenance to clean the surface is an effective way to keep the pores open and functioning (and prevent grass from growing!). However, this is generally not done and leads to performance problems.
The detail below illustrates a much more effective system for catching and containing roof sediment and debris before it enters the system. Any large debris such as leaves, or pine needles are stopped at the surface of the rock catch basin while small debris settles to the bottom of the catch basin, allowing clean water to flow out of the exit pipe into the base of the pervious concrete system. The large rock in the catch basin can be easily removed on a regular basis to clean out the accumulated sediment.
A well-designed and installed system will perform at a high level for a long time with minimal maintenance. If you are planning or considering utilizing a pervious concrete stormwater management system for your project, please feel free to contact us for design guidance and assistance.