Water Resources Research Act Program

Details for Project ID 2017MT319B

Student Fellowship Project: Influence of wood on sediment storage in a low order stream in the northern Rocky Mountains

Institute: Montana
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $769 Total Non-Federal Funds: $346

Principal Investigators: Robin Welling

Abstract: Sediment connectivity within a basin varies through space and time. It includes lateral, vertical, and longitudinal linkages, and the relative strength of these depends on the scale at which they are considered. The sediment delivery ratio, the ratio of downstream sediment output to input from basin erosion, approaches one in the long-term. Over time scales up to about 10,000 years, however, the sediment delivery ratio for a basin may be less than one. Hillslope-channel sediment connectivity is high in mountainous headwater streams because of steep hillslopes and narrow valleys. Steep mountain streams convey sediment downstream. Channels that are lower in the drainage network are sensitive to sediment supply due to their lower transport capacity. Sediment supply dynamics determine channel morphology, which in turn affects aquatic habitat and susceptibility to flooding. Determining the controls on sediment transport in headwater streams is a logical first step to understand sediment connectivity within a basin. Channel slope and confinement limit sediment storage in mountain streams. While sediment may be present in occasional bars and trapped behind boulders, wood obstructions are the most common sites of sediment storage. Wood has long been recognized for its important role in pool formation and influence on other aspects of stream morphology and aquatic habitat, but its role in sediment storage is a new and active area of research. Most research on wood-associated sediment storage has focused on the spatial nature and arrangement of wood. Only a few studies have considered the former’s temporal significance. The limited number of empirical analyses on wood-associated sediment storage and their focus on streams in northern coastal environments constrain our understanding of its temporal significance and its impact on sediment transport dynamics in other types of mountain streams. In particular, little research has focused on wood-associated sediment storage in semiarid and snowmelt-dominated mountain streams. While streams steadily recruit wood in wet environments, semiarid streams receive episodic inputs of wood and sediment. In addition, these streams may be especially vulnerable to climate change, and predicting their response to disturbance requires a better understanding of current wood and sediment supply dynamics.