Floodplain ecogeomorphic processes: interactions between floodplain forest characteristics, wood accumulations, and hydrogeomorphology

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Downed, dead pieces of wood in rivers and floodplains influence physical and ecological processes in river systems. Many river restoration efforts use wood to provide habitat for organisms, but wood on floodplains can also create habitat. However, very little is known about how wood is moved onto floodplains by rivers and then moved from floodplains back to river channels.

This project uses scaled physical models of rivers and floodplains (flumes), numerical modeling, and fieldwork to determine how flooding, forest characteristics, and physical characteristics of rivers and floodplains cause the deposition of wood onto floodplains. The results of the project will be presented to the river restoration community. The project will also create educational lessons using flumes for K-12, undergraduate, and graduate level students.

Downed, dead wood on the floodplain influences geomorphic processes and provides ecological benefits to river corridors. However, understanding the interactions between floodplain vegetation, wood, and hydrogeomorphology is a new frontier in geomorphic research, and numerical modeling of wood transport and deposition has only recently been developed.

This project combines flume experiments, numerical modelling, and field observations integrating floodplain forest stand characteristics, hydrogeomorphology, and wood transport and deposition during floods to assess the controls on wood deposition in floodplains and subsequent wood remobilization. The research objectives include (1) understanding the role of the forest stand density on the deposition and storage of wood in floodplains, (2) unravelling the importance of floodplain and channel morphology on floodplain wood dynamics, and (3) assessing overbank flow conditions needed to deposit and remobilize wood onto and from the floodplain to better understand wood jam formation and persistence.

Flume experiments will simulate different forest stand densities, overbank flow conditions, and wood transport regimes. The data gathered during the physical experiments will provide baseline information needed to develop empirical relationships for floodplain flow-forest-wood-morphologic interactions. The flume experiments will be used to test and enhance a 2D hydrodynamic model to further explore wood dynamics on floodplains, which will then be applied to a field site where large amounts of floodplain wood jams are present due to a recent flooding event.

The results of the project will be disseminated to management agencies and restoration groups in the US and Europe that are incorporating floodplain wood into efforts to enhance floodplain ecosystem functioning. This project will also develop K-12, undergraduate, and graduate level flume laboratory assignments and lessons on floodplain dynamics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.