Introduction

Societal use of rivers is important to meet many human needs, but has come at the cost of significant degradation to the fluvial ecosystem. Different people advocate for balancing the needs of the ecosystem and the potential of the human imagination for utilizing rivers at different levels for different rivers. For example, some people would prefer to see entire rivers or catchments left free of humans. Other people would prefer to divert nearly all water from rivers for agriculture. Most people do not want an "all-or-nothing" outcome, but a reasonable balance among natural values and societal opportunities.

We propose that in the case where a high level of human alteration to a river will be maintained, benefits to the ecosystem are possible primarily through active, science-based river rehabilitation. The spawning habitat integrated rehabilitation approach (SHIRA) is one example of this. Although the name emphasizes "spawning", the approach is in fact a holistic approach that values and addresses diverse species in their multiple life stages. Spawning of anadromous salmonids has proven an effective life stage to use as the indicator of the status and functionality of the entire river system. It is impossible to make high-quality, sustainable spawning habitat without also ending up with a diversity of habitats for other species and life stages.

The degree of benefits possible from river rehabilitation depend on the scale of action allowed. Within a river, there are three scales of rehabilitation usually contemplated: reach, geomorphic-unit, and hydraulic-unit scales. In the material that follows, we provide a basic background to the issues and concepts surrounding spawning habitat rehabilitation on regulated rivers.

Introductory Concepts