Due to the overflow of our drainage cisterns in the northern germany refuge garden lately, we took measures for the future, one of them being the flushing and clearing of the overflow pipe and its outlet. It was nearly completely buried in debris and foilage and any water coming from it would either flow back or accumulate at the outlet.
So we cleaned up everything and gave the area around the outlet a little reinforcement with old bricks. After testing it with about a third of the cistern’s volume (which is very much all at once) it was working beautifully and all the water seeped away within under 30 minutes. It seems vital to give the water a wide space to spread out so no backwater can build up. So far, so good.
We’ll have to see if the unsecured bricks will stay in place, otherwise we’ll have to pour some concrete and fix them permanently. Another possible addition might be a cover made from wire gauze to keep the foilage from clogging it up again.