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The Form and Function of Active vs. Passive: A Discussion on River Restoration

Geoffrey M. Goll, PE
Princeton Hydro, LLC
Ringoes, NJ

Authors:  Daniel T. Ketzer, PE.; Sumantha A. Prasad, PE.; Miranda L. Lepek

When discussing river restoration, the “why are we doing this restoration” is quickly overshadowed by the “how are we doing this restoration”. The focus shifts from purpose to credits and risk, which conflates stability with static-ness. When static becomes the expected outcome, we lock the design into active restoration; the construction of in-stream structures, bank treatments, and channel realignment to create the desired form of a restored river. This contrasts with passive restoration, the removal of constraints to a point in which the river is capable of regaining the functions of a restored river through natural processes. Active restoration requires intensive modeling and design costs paired with expensive construction costs. Any mistakes in design or construction can lock the river in a failing state it cannot naturally recover from. Passive restoration requires extensive understanding of the current stressors on the system and the capacity of the river to recover naturally paired with simple design plans and lower construction effort. Is there room for passive restoration in an urban environment? Is active restoration the only approach to protecting infrastructure and property? This discussion examines river restoration and dam removal projects that utilized active and passive approaches and compares the resulting forms as they relate to function.

About Geoffrey M. Goll, PE

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