River restoration is one of the most prominent areas of applied water‐resources science. From an initial focus on enhancing fish habitat or river appearance, primarily through structural modification of channel form, restoration has expanded to incorporate a wide variety of management activities designed to enhance river process and form. Restoration is conducted on headwater streams, large lowland rivers, and entire river networks in urban, agricultural, and less intensively human‐altered environments. We critically examine how contemporary practitioners approach river restoration and challenges for implementing restoration, which include clearly identified objectives, holistic understanding of rivers as ecosystems, and the role of restoration as a social process. We also examine challenges for scientific understanding in river restoration. These include: how physical complexity supports biogeochemical function, stream metabolism, and stream ecosystem productivity; characterizing response curves of different river components; understanding sediment dynamics; and increasing appreciation of the importance of incorporating climate change considerations and resiliency into restoration planning. Finally, we examine changes in river restoration within the past decade, such as increasing use of stream mitigation banking; development of new tools and technologies; different types of process‐based restoration; growing recognition of the importance of biological‐physical feedbacks in rivers; increasing expectations of water quality improvements from restoration; and more effective communication between practitioners and river scientists.

Water and sediment inputs are fundamental drivers of river ecosystems, but river management tends to emphasize flow regime at the expense of sediment regime. In an effort to frame a more inclusive paradigm for river management, we discuss sediment inputs, transport, and storage within river systems; interactions among water, sediment, and valley context; and the need to broaden the natural flow regime concept. Explicitly incorporating sediment is challenging, because sediment is supplied, transported, and stored by nonlinear and episodic processes operating at different temporal and spatial scales than water and because sediment regimes have been highly altered by humans. Nevertheless, managing for a desired balance between sediment supply and transport capacity is not only tractable, given current geomorphic process knowledge, but also essential because of the importance of sediment regimes to aquatic and riparian ecosystems, the physical template of which depends on sediment-driven river structure and function.

Connectivity describes the degree to which matter and organisms can move among spatially defined units in a natural system. River connectivity is typically described in longitudinal, lateral, and vertical dimensions within the river corridor and the watershed and can be conceptualized as a continuum from fully connected to disconnected over diverse temporal and spatial scales. Explicit characterization of connectivity helps understanding of disparities among short-term, local rates of flux and inferred fluxes over larger scales. Connectivity also strongly influences the response of rivers to natural and human disturbances. Investigations of connectivity facilitate the recognition of processes that cross traditional disciplinary boundaries, as well as understanding of nonlinear behavior and retention within rivers. Enhancing the ability to identify, quantify, and predict the processes that create and maintain connectivity is integral to the effective management of rivers.