Game of Stones: how does rock strength control river incision?

Theme: Solid Earth Dynamics

Primary Supervisor:

Byron A. Adams

Earth Sciences, UCL

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Secondary Supervisor:

Tom Mitchell

Earth Sciences, UCL

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Project Description:

Bedrock river incision is the key process that controls the response to changes in tectonics and climate in most mountain ranges. Models of landscape evolution commonly assume that river incision rate is proportional to shear stress on the channel and lump other factors into a term called erodibility. Our models are usually simplified in such a manner because we have methods for estimating shear stress, but the other variables that go into erodibility are much more difficult to constrain including the effects of lithology. However, high-quality geology maps are available for most places on Earth and generally outcrops of the rocks found in the river channel can be sampled in easier to access locations. We need a better technique for estimating the importance of local rock strength at the river reach scale and laboratory scale to find a fundamental relationship between the mechanical properties of core of rock and the resistance of these rocks to erosion in a river.
The student will focus on three primary tasks. 1) Develop methods for estimating the erodibility of rock samples in the laboratory setting. We have designed a new device for quantifying the erodibility of rocks as it relates to abrasion; however, its performance requires characterisation and standard operations procedures need to be developed for sample processing. 2) Measuring the mechanical properties of synthetic and natural samples. 3) Capitalizing on the lessons learned in the laboratory to create a scaled relationship between rock mechanical properties and bedrock erodibility in a river channel.

Policy Impact of Research:

Rivers set the pace and pattern of natural hazards around the world. To predict incision and sediment flux, and broadly how landscapes respond to changes in forcing factors such as anthropogenic, climate, or tectonic activity, the influence of rock erodibility needs to be constrained quantitatively.

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