Alteration of the creek by moving it, dredging it, building levees or dams can be very expensive to construct and maintain. Many of these actions aren't necessary if the stream is allowed to be natural with a buffer of trees. This is a way to save our tax dollars. A tree can absorb up to 1000 gallons of water a day, holding it so that the stream doesn't have to. This is a way to slow flooding.
Trees keep water cool enough to support fish and other wildlife.
If our creeks can't support wildlife it ultimately can't support us. This is a way to improve stream productivity. Trees filter many agricultural, household and industrial pollutants. Without such a filter the stream is much more susceptible to contamination. This is a way to slow down pollution.