A major change in park management came in 1994 when the city council voted to ban alcohol in all city parks with the exception of the 20th Street Park. The Parks Commission recommended the ban after reviewing the history of alcohol-related accidents and problems at Bear and Salmon Holes. At first, they just wanted to ban alcohol at the problem spots, not the whole park, but the city decided it would be confusing to include some areas and not others. Several studies completed in the last decade have looked at the impacts of usage, which is up sharply, he said. Even on real stormy days in the winter you can find a lot of people.
Usage is way up over ten years ago.
Without a doubt, he said, mountain bikers have more negative impacts than other user groups. Natural erosion of the Tuscan formation, the conglomerate mud flows that form the park's upper canyon, occurs at the rate of about a third of an inch every hundred years. Seven years later, after the number of mountain bikes in the park exploded, I can show you ruts in the Tuscan formation as deep as eighteen inches. When mountain bikes first came out, no one believed pedal power could cause the damage it does. Braking with knobby tires grinds off the top soil, which can start a chain reaction of erosion.