Mobility and Stability of Large Woody Material
Project ID: 3842
Principal Investigator: Christopher Cuhaciyan
Research Topic: Ecosystem Needs
Funded Fiscal Years: 2013
Keywords: lwd, stability, mobility, restoration, floodplain, river, flume, froude-scale
Little is known about the exact conditions under which large woody material (LWM) in rivers or on floodplains will move. The placement and management of wood in rivers and floodplains is becoming a common practice for restoring river forms and processes and is a key component of fish habitat and riparian restoration projects. In accordance with a trend toward more natural habitat improvement designs, river restoration is frequently turning toward a light but strategic touch, providing a kick-start in the right direction meanwhile allowing the power of the river to perform the majority of the improvements on its own. In the recent Science and Technology Program sponsored large woody debris workshop the safety of and failure mechanisms of large wood were prioroties, with the development of desing criteria as a high priority. This project seeks to provide basic research that will inform engineering design.
Understanding the most favorable locations to add LWM to a rivers floodplain based on incipient motion characteristics will inform natural habitat and floodplain restoration designs in support of Reclamations habitat improvement commitments and other ongoing restoration efforts. However, placing large wood in and near rivers constitutes a risk which is difficult to calculate. The risks can include the loss of constructed projects, or in more extreme cases, damage to or even loss of downstream infrastructure, such as bridges, pipes, and utility crossings. Deposition of large amounts of suspended wood can also lead to increased localized flooding. We propose to determine the conditions that initiate the movement of large woody material and answer the question, When does large woody material become mobile?
Need and Benefit
Large woody material is a natural and critical component of most river systems providing important structure to a river system by creating hydraulic diversity and river complexity. Physical diversity and complexity can be beneficial to a rivers ecosystem but may also pose a risk to infrastructure, property and even human life. The accumulation of LWM transported by a river has been the subject of much research over the past two decades (e.g., Evans, et al., 1993; Braudrick and Grant, 2001; Fox, 2001; Marcus et al., 2002; Abbe and Montgomery, 2003), but little has been done to learn what conditions are required in order to initially mobilize and transport downed wood already present on a rivers floodplain. Better understanding LWM incipient motion will improve the ability of water resource agencies, floodplain managers, municipalities, irrigation districts, and floodplain landowners to better manage floodplain accumulations of LWM and its potential benefit or risk.
Abbe, Tim B. and Montomery, David R. (2003) Patterns and processes of wood debris accumulation in the Queets river basin, Washington. Geomorphology, 51, 81-107
Braudrick, Christian A., and Grant, Gordon E. (2001) Transport and deposition of large woody debris in streams: a flume experiment. Geomorphology, 41, 263-283
Evans, Brent F., Townsent, Colin R., and Crowl, Todd A. (1993) Distribution and abundance of coarse woody debris in some southern New Zealand streams from contrasting forest catchments, New Zealand Journal of Marine and Freshwater Research, 27:2, 227-239.
Fox, Martin J. (2001) A new look at the quantities and volumes of instream wood in forested basins within Washington State. Masters Thesis, University of Washington College of Forest Resources.
Marcus, W. Andrew, Marston, Richard A., Colvard, Charles R., Gray, Robin D. (2002) Mapping the spatial and temporal distributions of woody debris in streams of the Greater Yellowstone Ecosystem, USA. Geomorphology, 44, 323-335.
This work would result in a graduate thesis (completed FY 2014), two presentations at appropriate scientific conferences, and a peer reviewed journal article which would be expected to be published shortly after project completion in FY 2015.