Large and costly flood events can occur when warm storm systems deposit heavy rainfall on snow-cover, especially in mountainous areas.  Flood forecasters and reservoir operators lack guidance on how this flood risk will respond to climate change at the scale of mountain river basins. In a recent study, we assessed future changes in rain-on-snow flood risk over western North America. We find the associated flood risk will shift to historically colder regions with flood volumes more than doubling in some regions of the Sierra Nevada and the Rocky Mountains. The results are reported in a new paper in the journal Nature Climate Change.   Read-only version (free):

Increases in winter snowmelt

Photo by Lars Peterson

Research topics

How does forest cover influence our water resources?

Using a process-level approach that relies upon observation and models, my work examines how forest cover alters the surface energy and mass balance. Ongoing research projects serve to build a holistic understanding of the net effect of forests and forest management on basin water yield and seasonal runoff timing - and how these processes are linked to climate, latitude and landscape properties. 


How will Alaskan & Yukon River, Fish, and Communities be affected by climate change?

Uncertainty of windflow prediction methods in mountain hydrology 

In alpine regions, wind plays an important role in determining snow redistribution (drift and scour) patterns, which influence the duration and spatial patterns of spring and summer meltwater availability in headwater basins. An ongoing project in the Canadian Rockies evaluates the hydrological uncertainty associated with windflow representation methods commonly used in snow models.

Photo by Angus Duncan

Future changes in rain-on-snow flood risk

I am leading an exciting, multidisciplinary research project funded by the National Science Foundation’s Navigating the New Arctic Program. The project seeks to assess climate change impacts on hydrology, rivers, fish, and Indigenous communities in Alaska and upstream western Canada.

As the Arctic and its rivers continue to warm, the impacts on people, their fisheries, and winter travel routes are unknown. Better understanding of the possible future changes requires close partnership among Native communities and scientists from diverse fields of study. Strong collaboration with Tribal and First Nation communities, community-based science networks, and environmental professionals will guide the science and facilitate monitoring and modeling. Partners include the University of Colorado, the USGS, the National Center for Atmospheric Research, the Yukon River Inter-Tribal Watershed Council, the Institute for Tribal Environmental Professionals at Northern Arizona University, the University of Saskatchewan, and the University of Waterloo

My research interests and experiences are on the topics of terrestrial hydrology, hydrometeorology, and remote sensing in mountainous and forested seasonally snow-covered environments.

I evaluate the availability of freshwater in these environments and the physical mechanisms and pathways responsible for its evolution.

Seasonal and inter-annual snow accumulation and melt patterns 

Accurate seasonal runoff predictions in mountainous regions require a process-based representation of how snow accumulation (e.g. precipitation, wind redistribution) and ablation (e.g. melt, sublimation) vary in time and space over complex terrain. A project in the southern Sierra Nevada of California evaluates when and where meltwater is available to the soil and river systems and how these processes vary with seasonal meteorology, land cover, elevation, and climate conditions.

Slower snowmelt in a warmer world

Click here to access a read-only version of the paper:
In regions where snow is an important component of the annual water budget, it is vital for water and land managers to understand potential climate change impacts on snow water resources and reliant human and ecological systems. There is general consensus that projected warming will cause earlier snowmelt, but how snowmelt rates will respond is both poorly known and a critical determinant of future streamflow.

In a project conducted at the National Center for Atmospheric Research, historical observations and climate model simulations are used to develop and test a hypothesis that snowmelt will be slower in a warmer world. The results are reported in the journal Nature Climate Change

Snowpack in mountainous regions is an important source of water for more than a billion people globally. This resource is also highly sensitive to climate change. In a recent study, we evaluate long-term trends in snow water resources using data from observation stations across western North America. We find that while snowpack magnitude has declined at 11% of stations, winter snowmelt has increased in a widespread manner at three-times the number of stations with snowpack declines. We conclude that winter melt is highly sensitive to warming and thus is a compelling indicator of change in snow water resources that may be muted in commonly used snow water equivalent metrics. The results are reported in the journal Nature Climate ChangeRead-only version (free):

  -  Water resources

  -  Hydrology

​  -  Forest hydrology 

  -  Hydrometeorology

  -  Snowmelt modeling

  -  Climate change

  -  Remote sensing of surface processes

  -  Ground-based measurements

  -  Forest radiation models

  -  Snow - forest interactions

  -  Micrometeorology

​  -  Data visualization