I missed this article when it came out in 2014 but it makes fascinating reading in light of the flooding in Ireland and Britain at the moment.
Water sinks into the soil under trees at 67 times the rate at which it sinks into the soil under grass. The roots of the trees provide channels down which the water flows, deep into the ground. The soil there becomes a sponge, a reservoir which sucks up water and then releases it slowly.
Read the article for the full context. I wonder why more action on forestation of hills isn’t being done.