Which material drains the most water sand topsoil or mulch?

Answer 1

Mulch is a cover that will either absorb water or let it through, depending on the kind of mulch. A 2-inch layer of wood chips for instance will absorb only a little water and drain most of it. Sand absorbs a bit more, but also lets most of it through.

Neither will drain any water if they are not connected to a drainage system of pipes to evacuate the water. It will stay stagnant otherwise.

A common material used for drainage systems is a bed of gravel, with porous pipes at a slight inclination onto it, and more gravel put on the sides and top of the pipes.

The pipes themselves are usually clothed with some cheap recycled fabric to prevent the dirt from blocking the drainage holes in the pipes.

If you do not have a drainage system and simply want to know what material will absorb the most water to prevent most rain floodings, you can use a mulch of peat moss, or even better, incorporate it into the top soil. It absorbs several times its weight in water. It is a bit acidic though, so don't forget to add lime to reestablish the original acidity level of your soil.