I am a research professor in the UMass Amherst Geoscience department. I am interested in how human perturbations to flows of water and sediment affect physical and ecological systems. This broad interest is divided into a few main study areas:
- How do coastal conditions drive the evolution of tidal wetland systems? What changes can we expect in a warming climate with increases in extreme weather and the rate of sea level rise.
- How do changes in catchment processes – both local land use and climate-related – affect the delivery of sediment from upland areas to lakes, reservoirs, and the coast.
- How do riparian aquifers adjacent to rivers respond to natural and anthropogenic changes in river discharge?
Statement on Inclusion in the Geosciences
One of the thrills of working in research is the impact that our results and findings can have to make people’s lives better and improve the world. That happens best when a diversity of viewpoints are represented.
The discipline of geology is one of the oldest in western science, with a rich history and many exciting discoveries that have changed worldviews around the globe. The same history is rife with unfortunate wrongs that we must reckon with: colonialism, extraction and environmental harm, environmental injustices, sexism / misogyny, and racism. I strive to help with the dismantling of these harmful forces that are still with us as a discipline. Here are some things that I am doing along these lines:
- Support departmental participation in AGU Bridge
- Actively amplify the voices and research findings of scientists from minoritized backgrounds
- Serve on the departmental DEI committee since 2018
- Introduce students to fieldwork in a way that is inclusive and intentional about reducing harm and risks to folks from minoritized backgrounds
- Volunteer work with Fort River Watershed Association to provide more outdoor opportunities to environmental justice communities.
- Actively recruit students from underrepresented backgrounds to work in my lab and on research projects
- *please reach out if you have more ideas
Here are some current projects that I am working on:
Dams and Sediment on the Hudson– along with collaborators at Woods Hole Oceanographic Inst. and the Hudson River National Estuarine Research Reserve, we are helping river managers and dam owners better understand the sediment impacts of dam removal on the Hudson River estuary. With input from an advisory committee made up of stakeholders with a variety of perspectives, this project produced a tool for dam owners to make an initial assessment of sediment inventory in their dam as they weigh dam removal. Three papers are forthcoming: (1) aggregate impacts of dams trapping sediments; (2) response of Hudson tidal marshes to channel modifications; (3) turbidity hysteresis following 2011 Hurricane Irene. Data from this project can be found at UMass Scholarworks data repository.
Manuscripts from this research:
Dynamic Tidal Wetlands – Current and projected rates of sea level rise threaten to drown tidal marshes along coastlines. Tidal marshes mitigate storm impacts to vulnerable coastal infrastructure and provide myriad ecosystem services. I am currently working on tidal wetlands in the Northeast US and the Caribbean Islands that have undergone dynamic growth or decline over the last 100 years. Selected study sites have all experienced a dramatic change in coastal morpholoogy or hydrology which likely catalyzed rapid marsh growth or decline. By studying the conditions that allowed for rapid marsh expansion or collapse, we can better prepare to seed new marshes and restore those that suffer as sea levels continue to rise.
High Resolution Mapping of Blue Carbon
Roughly a third of global CO2 emissions have been absorbed by the ocean, with much of that carbon stored as organic material in tidal wetlands. Tidal wetlands are uniquely able to store carbon, making them essential tools to mitigate global CO2 emissions. First, temperate tidal wetlands display exceptional levels of net primary productivity, rivaling mature tropical rain forests. Second, they trap allochthonous carbon as they accrete sediment. Third, rather than plateauing at a stable total carbon content as would be expected in most terrestrial ecosystems, tidal marshes continually store additional carbon as they accrete in step with sea level rise. As a result of this continual accumulation, salt marshes annually store roughly twenty times more carbon per unit area than forests. In light of the growing value of carbon, with stored carbon stocks valued in excess of $100 per ton and projected to increase to more than $200 per ton by 2050 (2007 dollars), an estimate of future carbon storage will add to the urgency to restore tidal marshes. Given the likely development of carbon markets in the near future, accounting for the value of carbon stored in tidal wetlands aligns closely with USDA’s mission to expand economic opportunities in rural America.
In order to estimate blue carbon burial rates and total inventories within Northeast US tidal marshes, I have broken this broad goal into four components as follows:
- Develop pedotransfer functions for Northeast US marshes that relate carbon burial rates at each point within a marsh based on their geomorphic classification and distance from tidal creek network and lidar-derived elevation.
- Relate total carbon inventories to marsh geomorphic context. Test accuracy at sites with known marsh peat volumes and carbon content to provide error bounds.
- Classify all Northeast US tidal marshes according to geomorphic setting and estimate total carbon inventory of each.
- Quantify blue carbon burial rates in tidal marsh soils for the Northeast US using a lidar big data approach (~5E8 pixels in study domain).
Historical Perspectives on Sediment Mitigation– Along with Scott Steinschneider and Keith Ahn (both of Cornell), I am studying the sediment archives in one of New York City’s largest water supply reservoirs. NYC is one of five municipalities in the country that holds a filtration avoidance permit from the EPA, allowing them to distribute unfiltered (but treated) water to its customers. This permit was acquired and is maintained through NYC’s exceptional watershed management program, which ensures high quality source water. Sediment in the reservoir’s bottom informs us as to how well various measures over the last century have fared in reducing sediment loading of the reservoir. This is the first paper that has come out of this research.
Sustainability and Hydroelectricity– Hydroelectric power is often touted as a clean solution to energy challenges. However, hydroelectric generation comes with myriad well-documented adverse effects. Along with Eve Vogel and others at UMass, I am studying how changes to energy markets have affected the operation of hydroelectric facilities and in turn affected downstream river reaches.
Extreme Event Sedimentology – Destructive floods from rainfall and coastal storm surge can leave sedimentary layers in lagoons, reservoirs, and lakes that are distinct from background sedimentation. I use sediment cores to understand changes in past frequency and magnitude of these extreme events. By coupling modern observations with sedimentology, we can extend inferences from often short-term gauge records to longer time-spans. Ongoing research is examining the erosivity of Hurricane Maria in the uplands of Puerto Rico.
Hydropeaking and Riparian Forests– Hydropeaking – hydroelectic dam releases corresponding to periods of energy demand and price increases – has been shown to cause water to be lost from downstream river reaches. During a release, river water downstream of the dam is pushed into the bank, removing much of it from the river and denying it from downstream users such as farmers, municipalities, and ecosystems. I am studying how this water is taken up by trees and to what extent hydropeaking robs rivers of their water.
I am also interested in the development of floodplains over time and combining records of sedimentation and forest development in floodplains. This paper, with collaborators Christian Marks and Keith Nislow, shows how geomorphic conditions in floodplains influence tree bioproductivity.
Teaching I have a masters of education in secondary science and taught for three years as a Teach for America corps member at a public school in rural Hawaii. As an instructor at UMass, I was awarded the university’s most prestigious teaching award (two awarded per year). Here are some courses that I have taught:
- Introductory Geology
byellen < a t > geo.umass.edu