one passive "first water exclusion" system that I though was pretty well designed has several (depending on the height of your house) vertical stand pipes of large diameter 4" or so PVC connected to your eaves system...the pipes must fill first before the cascade overflow at the top then goes on to the next pipe then to storage totes... a clean out plug at the bottom allows removal of large debris not screened by the eaves, and left slightly ajar(or drilled with a small hole) to allow water to slowly drain from the stand pipe after the storm