The fluvial ecosystem of mountain rivers provides dynamic habitat with ecological niches for numerous threatened species. The natural soils surrounding such rivers typically consist of sand, gravel, and cobble, which creates an active hyporheic zone, the subsurface region that exchanges water and matter with the surface water. Fish require a functional hyporheic zone with a porous matrix, both for spawning and for foraging for macrozoobenthos, which thrive in the shelter of coarse sediment. Natural or artificial mobilizations of fine sediment (e.g., through engineering interventions) may clog the porous matrix and impact the river ecosystem. Clogging of the sediment matrix results in soil consolidation, which reduces hydraulic conductivity and oxygen content, leading to limited ecological functionality of the hyporheic zone. Once clogged, the ecological functions can only be recovered through active stream restoration. Recent research has shown that parameters characterizing the sediment matrix (e.g., compactness or oxygen concentration) reflect the degree of clogging and provide a measure of restoration success. The introduction of vegetation or large wood pieces (e.g., tree stems) into a river is a common restoration measure used to enhance habitat dynamics. Large wood additions can locally elevate turbulence levels, and thus, potentially offset or eliminate clogging. This hypothesized connection between large wood and riverbed clogging has not yet been assessed, but is highly likely to improve restoration design. By combining MIT’s expertise in vegetation hydrodynamics with the IWS’ expertise in riverbed clogging processes, this collaboration will draw a scientific baseline for future research aiming at insights into river physics and restoration ecology.
From 2021.05.01 to 2023.01.31