Nature provides the perfect means of processing storm water. Storm water seeps downward, traveling through purifying soil, rocks and other natural barriers before entering ponds, lakes and streams. Roads disrupt this natural cleansing by creating runoff, water laced with road-top residue (oil, rust, rubber, metals, gases and more) that's forced to take unnatural routes. The traveling liquid picks up toxins along its way, such as fertilizer and motor oil, and in its wake leaves high concentrations of toxins on vegetation, causes soil erosion, and too quickly enters natural waters without benefiting from nature's slow purification process.
Are some roads worse offenders than others? Let's look at the types of roads and their compositions.