Slug and Snail Trap

This year in spring I found slugs everywhere. So I have declared war to them.
This trap includes a watering system. Slugs like to have cold and humid. The green roof has a water basin in the middle to cool in sunshine. Both roofs have water channels down to bottom. Make a groove in the ground, it will be humid there. Slugs will sleep there over the sunny day and you can find them. This groove has to be humid but not a lake, slugs are afraid from water because they cannot swim. This model file