Instream large wood enhances the benefits of e-floods in regulated
mountain rivers
Abstract
Environmental high flows, or e-floods, released from dams to restore
aquatic and riparian habitats are a key management strategy to mitigate
the impacts of dam regulation. While there is extensive literature on
the design and implementation of e-floods, the role of instream large
wood—downed trees, trunks, branches, and root wads—in enhancing
e-flood outcomes in regulated rivers has not been adequately explored.
This paper presents insights from the Spöl River in the Swiss Alps,
where years of observations highlight the significant impact of large
wood on the success of e-floods. Large wood contributes to
geomorphological dynamics, increases habitat complexity, and enhances
ecosystem resilience, yet it has been largely overlooked in e-flood
planning. The study argues that the inclusion of instream wood can
define the difference between success and failure in e-floods by
supporting the continuity of the wood regime, which, along with flow and
sediment regimes, is crucial for ecological integrity, and emphasizes
the importance of integrating wood management into e-flood design. The
Spöl River serves as a case study, demonstrating how wood management
during e-floods can restore or sustain essential functions, ultimately
improving the ecological health of river systems. The insights gained
can be applied to the management of other regulated mountain rivers.