Managing floods in Urban catchments: Experiences in Denver area (Colorado, USA) and Geneva (Switzerland)

Abstract

As Denver, Colorado, began its rapid growth in the 1960s, two major floods led to the formation of an extensive flood control district, which adopted a two-pronged approach: Through land-use regulation, it prevented further development in floodplains. In already-built floodplainareas, it removed houses where possible and elsewhere used structural measures to reduce flood hazard. The result is fewer houses vulnerable to flooding than before, and large riparian parklands, providing ecological and social benefits. The River Aire flows north and east from the French Alps to central Geneva. About 5 km of the river was channelized in the nineteenth century to provide better drainage, but this conveyed floods faster, increasing flood risk downstream. Restoration of the Aire River included two extensive, shallow impoundments on the floodplain to reduce peak flows downstream and a highly innovative approach to allowing for a dynamic channel within a framework of multiple possible channels from which the river could adopt a course.