Introduction to Temperate Floodplains

Floodplains are among the most dynamic, productive, diverse, and threatened ecosystems in the world (Tockner and Stanford 2002). Intact and restored floodplains generate major environmental benefits that provide significant support for local and regional economies, most notably through flood-risk management, fisheries, recreation, and seasonal agriculture (Postel and Carpenter 1997). Yet the flooding that defines floodplains — and drives their ecological productivity and diversity — is often viewed as a problem. Many floodplains sustain dense human populations and agriculture that is not compatible with inundation. Floods in industrialized countries are usually equated with disaster, prompting extensive construction projects, such as dams, levees, and channel straightening and dredging, to minimize flood impacts on the built landscape. Consequently, floodplains, particularly temperate floodplains in more developed countries, are among the most altered landscapes worldwide, most with ecosystems that are highly degraded (Tockner and Stanford 2002). Yet floodplains also present some of the best opportunities throughout the world for innovative management that reconciles human uses and environmental conservation.

In this book, we focus on floodplains in temperate regions of the world, interweaving floodplain science and management. We review fundamental processes that shape floodplains as biophysical systems and then consider new perspectives on how floodplains are managed. Thus, this book should be of interest to both scientists and managers. We strongly believe that the most promising future for temperate floodplains will arise through management solutions that allow them to function as dynamic ecosystems that are also productive and safe components of the human landscape. Achieving this future will depend on informed dialogue and collaboration among managers, scientists, and stakeholders. Our experiences with temperate floodplains lead us to believe that the long-term social and environmental sustainability of floodplains can best be guided by the interrelated concepts of "novel ecosystems" and "reconciliation ecology." Novel ecosystems are those that are highly altered by humans and often contain alien (nonnative) species, such that their current biota and physical structure may differ markedly from those of the ecosystems they replaced. Nevertheless, they may be functionally quite similar to the original ecosystems (Hobbs et al. 2009, 2013, 2014; Moyle 2013). Reconciliation ecology is the "science of inventing, establishing, and maintaining new habitats to conserve species diversity in places where people live, work, and play" (Rosenzweig 2003, p.7). Reconciliation ecology focuses on conservation of native biodiversity while accepting the reality that virtually all habitats have a strong human presence. Thus, built landscapes, such as cities or flood-management systems, can be treated as novel ecosystems into which biodiversity conservation and ecosystem services are actively integrated in order to provide multiple benefits to human society.

The concept of novel ecosystems is generally applicable to floodplains of large temperate rivers because virtually all are modified and/or regulated. While channels and floodplain surfaces continue to be reshaped by flood frequency, extent, and duration, these forces are modified in large part by the operation of dams, levees, and drainage systems. Even most "restored" floodplains have topography that has been highly altered by agriculture and are subject to inundation regimes managed by people. Species assemblages are often in continuous flux, responding to environmental change, land and water management, and invasions of non-native species.

Because of this ecological novelty and because large areas of temperate floodplains have been converted to other land uses, reconciliation ecology provides a constructive framework for moving forward with sustainable management of floodplains for multiple purposes, including flood-risk management and conservation. People are now an integral part of nearly all temperate floodplain ecosystems and, in the chapters ahead, we will illustrate how reconciled floodplain ecosystems can provide ecological and economic benefits.

The floodplains of California's great Central Valley (figure 1.1), which inspired this book, provide a particularly cogent example of the complex and evolving relationship between people and floodplains. These floodplains have undergone ecological loss and sweeping landscape change, but they also provide examples of paths toward a more sustainable future. We draw heavily on this well-studied landscape as its lessons can be applied globally and reinforced by examples from other floodplain systems.

In short, this book is about reconciling temperate floodplain ecosystems with society's demands on the environment; it is also about how people can work proactively with novel floodplain ecosystems to generate multiple benefits. Our goal is to demonstrate that maintaining native biodiversity and natural floodplain functions can be highly compatible with a broad range of societal objectives and expectations. Innovative management approaches can produce floodplains that provide habitat for some of the world's most spectacular fish and wildlife, while also protecting communities from floods and providing clean water and open space for people. Our ambitious objective is to have the concepts, examples, and syntheses of emerging ideas in this book serve as a foundation for effective and sustainable management of temperate floodplain systems. We hope that this foundation will also provide insight for global floodplain management beyond temperate regions.

GEOGRAPHIC SCOPE AND THE DEFINITION OF FLOODPLAINS

Strictly speaking, the floodplains covered in this book occur within temperate latitudes, defined as those between the Arctic Circle and the Tropic of Cancer and between the Antarctic Circle and the Tropic of Capricorn (spanning the latitudes of 23°26? to 66°34? both north and south). Mountain ranges and other continental features greatly affect river flows and temperature patterns, so floodplains vary in size, character, and importance throughout the temperate regions. We primarily focus on floodplains from North America, Eurasia, and Australia, with limited mention of those in...