Downstream Ecological Effects of Dams

TLDR

Damming alters river flow, sediment, nutrients, energy, and biota, disrupting most ecological processes. The article argues that geomorphological analysis is essential for river conservation and management, illustrating how subtle geomorphic adjustments can profoundly affect downstream ecological relationships through three case studies and a proposed mitigation framework. The authors present three case studies—channel simplification and salmon decline on the McKenzie River, channel incision and reduced floodplain inundation on the Oconee River, and increased stability of a braided river in New Zealand’s South Island—and outline a geomorphology‑based approach to assess and mitigate dam impacts by tailoring design and operation. The article includes 41 references, 10 figures, and 1 table.

Abstract

The damming of a river changes the flow of water, sediment, nutrients, energy, and biota, interrupting and altering most of a river`s ecological processes. This article discusses the importance of geomorphological analysis in river conservation and management. To illustrate how subtle geomorphological adjustments may profoundly influence the ecological relationships downstream from dames, three case studies are presented. Then a geomorphically based approach for assessing and possibly mitigating some of the environmental effects of dams by tailoring dam designed and operation is outlined. The cases are as follows: channel simplification and salmon decline on the McKenzie River in Oregon; Channel incision and reduced floodplain inundation on the Oconee river in Georgia; Increased stability of a braided river in New Zealand`s south island. 41 refs., 10 figs., 1 tab.