Past Research Pics  

Boston College

Department of Earth and Environmental Sciences

Environmental Studies Program

 
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Past Research Summary
Flow resistance: how mountain streams dissipate energy

Accurately quantifying flow resistance is important for predicting flow velocity and discharge.  Velocity reflects the balance between the energy it takes to move water downhill and the resistance to flow.  Better predictions can be used for estimating flood flows, which is needed for the design of fish passages, culverts, and small dams in these mountain channels. Therefore my PhD work focused on developing a more detailed understanding of the energy losses in a mountain stream (David et al., 2010a,b; David et al., 2011; Yochum et al., 2012; David et al., 2013).

Flow reistance and channel morphology

Channel morphologies found in East St. Louis Creek, Fraser Experimental Forest, Colorado
Flow resistance varied significantly by channel morphology, for a given gradient and discharge.

Review of headcut mitigation techniques

I developed a technical report to summarize the state of our knowledge on how to rehabilitate an incising channel with a migrating headcut and to provide assistance for forest managers on how to plan a rehabilitation project for this type of stream. Channel incision, and headcut migration, causes a drastic change in the landscape that can disrupt land used for agriculture, threaten adjacent structures, cause changes in environmental conditions such as reducing water quality and increasing nutrient loads, accelerate aridification of the land, and increase the production of sediment. Channel incision is a concern throughout the world because of loss of land, particularly farmland, from erosion. I reviewed techniques that have been used around the world and determined how successful these projects were to meeting rehabilitation goals.

Summary of structures reviewed for technical report

Summary of the types of methods reviewed in the technical document (left) and the major goals of each of the rehabilitation projects (right).
The bar graph on the left shows both the number of studies that are reviewed in this technical document for each method and divided by climatic region. Many of the studies were done in a semiarid climatic region. The pie chart on the right shows the major goals for each of the studies. The main goal is identified as "Headcut" when the structure has been used to stop a headcut from migrating, "Incision" when the goal is to stop a channel from continual incision, "Habitat" when the focus is habitat enhancement within an incised channel, and "Gully" when the focus is to prevent gully development within a drainage basin.

Impacts of ski slope development on mountain streams

My past research focused on the effects of land use alterations on stream channels, emphasizing my interest in the interaction between human activity and surface processes.  I concluded that stream sensitivity to land use change was based on topographic controls, type and density of riparian vegetation, and the underlying geology.  The findings from this project were used by the USDA Forest Service to develop new management practices for developing ski areas in the Rocky Mountains, which highlights my interest in using research to assist in developing best management practices in rivers (David et al., 2009).

Undercut Banks

Impacts of ski slope development on streams in the White River National Forest
Comparison of impacts in basins with granitic versus sedimentary bedrock (click for larger image).

 
 

 

Flow Resistance

Fieldwork in Fraser Experimental Forest, CO
3-D velocity was measured with an Acoustic Doppler Velocimeter (ADV) on a plane bed reach on East St. Louis Creek (David et al., 2013).

Fool Creek, Fraser Experimental Forest, CO

Wood in steps on Fool Creek in Fraser Experimental Forest, CO
Streams with larger wood loads were found to have significantly higher flow resistance than streams with little to no wood. In particular, wood increased step heights creating larger drops and increasing flow resistance (David et al. 2010a,b; David et al., 2011).

Ski lifts on Snowmass Mountain, CO

Ski lifts on Snowmass Mountain, Colorado
Development of ski slopes include ski runs where trees have been permanently cleared away, machine-grading of slopes in the summer, road construction, and snow-making in the winter (David et al. 2009 ).

Keystone Ski Area

View of Keystone ski slopes from Lenawee Mountain in Keystone, Colorado
Photograph shows areas where trees have been permanently cleared from the watershed (David et al. 2009 ).