Side channel evolution and design: achieving sustainable habitat for aquatic species recovery
1. How do side channels form and evolve in both sand and gravel bed river systems?
Side channels in natural river corridors are created and maintained as a result of a number of processes related to the morphology and geology of the river corridor and floodplain, the hydrology of the watershed, the sediment supply and size, and the amount of large wood within the system. A global understanding of how side channels form and evolve over time currently does not exist.
To achieve this understanding of side channel form and process, we propose to conduct an empirical study of side channels across the variety of river systems represented in our study areas. This study would evaluate a range of variables that characterize side channels in terms of their form, location and angle of inlet from the main stem of the river, their frequency of inundation (perennial to intermittent), the type of habitat they provide (target species life stage served) as well as their evolution over time (see Task 2). The outcome of this study would be a classification of side channels and a conceptual model describing the side channel life cycle.
2. A sustainable side channel is one that is able to maintain habitat function over time, either as a single channel or as part of a network within a floodplain. Though a sustainable channel may evolve over time, the biological, geomorphic, and hydraulic characteristics will continue to provide intended habitat function. In some cases there may be a desire for side channels to not evolve over time and to maintain their constructed forms. In some cases it may not be feasible to design a long-lived side channel and a network approach with multiple inlets may be required. Whether they are intended to evolve or not, we currently lack a comprehensive understanding of how to design side channels as well as how environmental flow releases and other management activities affect side channel evolution.
A corollary to this question is how long should
Need and Benefit
Need: Reclamation, its federal and local partners, and the public have an interest in funding habitat restoration
designs that will improve on existing conditions and play a positive role in species recovery. Constructed side
channels represent an important and widely used approach for habitat restoration. For recovery program managers to
better quantify the habitat benefit resulting from their restoration efforts, they need to be able to evaluate the evolution
of habitat suitability over the lifespan of a constructed side channel. Each species recovery program has internal
systems for evaluating project success and applying lessons learned on future restoration work. However, to date no
broad synthesis of side channel processes and design recommendations has occurred. Without synthesizing
restoration project performance across the many programs in which Reclamation is involved, we will not be able to
draw upon lessons learned in other programs and may continue to fund the design and construction of sub-optimal
and uncertain habitat restoration designs. Because our team has existing relationships with the many recovery
programs, we are well-positioned to serve as the institutional framework for integrating information.
Benefit: With a better understanding of side channel processes and the evolution of habitat suitability over time,
species recovery program managers can better allocate their resources and have more effective recovery programs.
More effective species recovery programs will decrease the potential for future legal battles and ensure continued
water delivery and hydropower generation.
Urgency: Each year Reclamations spends tens of millions on habitat restoration and maintenance. When habitat
restoration does not perform well, recovery programs and Reclamation run the risk of greater scrutiny and even
lawsuits from conservation groups. All of this can serve to impact Reclamations core missions of water delivery and
power generation and increase compliance costs.
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