Flooding is the most damaging natural disaster in the world, with average annual losses exceeding $40 billion (Cooley 2006). These damages have been increasing through time and flood risk will continue to rise due to population growth in flood-prone areas, climate change contributing to more intense storms, and the aging of flood-management infrastructure. (See Case Studies below)
This infrastructure—including dams, levees and floodwalls—has been the traditional response to managing flood risk. How-ever, the successful performance of this infrastructure necessarily eliminates one of the most important ecological processes on Earth: the connection between rivers and floodplains. This connection is what makes river-floodplain systems among the most productive and diverse ecosystems on the planet (Bayley 1995). Throughout Africa, Asia and Latin America, river-floodplain systems support productive fisheries and agriculture, providing a primary food source for hundreds of millions of people in rural communities (UNEP 2010).
River basins with extensive flood-management infrastructure have lost this essential connection between rivers and floodplains, resulting in dramatic declines in river productivity and biodiversity. In fact, freshwater species are endangered at higher rates than either terrestrial or marine species, in large part to the fragmentation and changes in flow from infrastructure (Richter et al. 1997, Ricciardi and Rasmussen 1999).
Thus, river floodplains present two great challenges to those seeking sustainable management of the world’s rivers: the need for actions to reduce flood risk and the need to maintain or restore the connections between rivers and flood-plains. At first glance, those objectives seem incompatible. In this report we describe how a “green infrastructure” approach to flood-risk management can address both objectives. This approach incorporates natural features and processes into flood-management projects. The techniques and approaches described here are intended to reduce flood risk for people. However, unlike engineered infrastructure, green infrastructure approaches can also include restoration or conservation of forests, wetlands, rivers and floodplains. When implemented as part of an overall strategy for sustainable river and watershed management, these approaches provide not just the primary benefit of flood-risk reduction, but also support a diverse array of other benefits.