Grasses and other herbaceous vegetation in zone 3 tend to increase soil porosity allowing greater infiltration and water storage potential.
Dense grasses slow the flow of surface water and spread the flow more evenly over the landscape.
Reducing the velocity of the water flow allows sediment to settle out, allows time for pesticides to degrade and permits increased uptake of excess nutrients.
Grasses can potentially be used for forage, hay or other products.