Hi guys

I'll soon be creating a drainage model to show how drain systems work, which will include a car park, warehouse building a landscape and river at the side base. I'm guessing the size will be about 3 foot by 3 foot. In order to get the frame (on which all this will sit) I have thought about using chicken wire and then coating this with papier mache, removing the wire and then painting it or varnishing it to make it waterproof. It needs to be sturdy to hold water and some soil. Any thoughts that will help? i.e. will chicekn wire spacing be fine enough (are there cheap enough alternatives?); what ratio of flour/water/glue to use? what is best and cheap to waterproof the papier mache?

Cheers in advance.