This invention is a Low Impact Development (LID) solutions system called Drainage Block that is effective for retention of rainfall on paved areas in average as well as in extreme conditions. The system is developed for roof runoff but the general idea can also be applied to delay runoff from roads parking lots and in small canals. The Drainage Block is very well applicable in a modular system. Modular application in large paved areas will create nearly endless possibilities to spread the runoff from rainstorm events.