This map represents areas where water, such as from rainfall, cannot naturally soak into the ground. When water cannot soak into an impervious surface, it runs off downhill towards the nearest water body, often picking up and carrying pollutants along with it. Not only do these data help with modeling potential water pollution sources, but also can be used to quickly visualize more densely and less densely populated areas, and model the sprawl of human development.
Source: RI Digital Atlas