THE UNIVERSITY OF WASHINGTON PERMEABLE PAVEMENT DEMONSTRATION PROJECT– Background and First-Year Field Results

Wherever grasslands and forest are replaced by rooftops and roads, the movement of water across the landscape is radically altered. Some of these changes are intentional, and they render the land more useful for the purpose for which it has been altered. Yet some of the changes are unintended and can have severe consequences. Flooding, channel erosion, landsliding, and destruction of aquatic habitat are some of the unanticipated changes that can also result from these alterations, recognized by many decades of studies (e.g., Wilson 1967; Seaburn 1969; Hammer 1972; Leopold 1973) because of the loss of both lives and property that sometimes result. With urbanization, stream channels expand catastrophically to consume adjacent land never before affected by either flooding or erosion, sediment inundates low-lying areas seemingly far away from active channels, stormwater facilities are overwhelmed by frequent flows far beyond their design capabilities, and populations of aquatic organisms are decimated.