Case Western Reserve University highlighted my most recent publication in Nature Communications about floods, floodplain sediment, wildfire, climate, and erosion along Rocky Mountain rivers. The journalist and author of the article, Mike Scott, asked me about similarities and parallels with urban rivers in the East. Check it out!
A portion of my dissertation research that quantified the duration fine sediment resides along the area adjacent to a river before being eroded (floodplain sediment residence time) and examined the role of valley geometry on the impact of extreme floods was just published in Nature Communications!
This paper shows that mountain streams at higher elevation in the Colorado Rocky Mountains store fine floodplain sediment for longer durations (>1200 years) than those below the Pleistocene glacial terminal moraine (<200 years). In addition to differences in glacial history associated with elevation, these differences in floodplain sediment residence times reflect differences in dominant vegetation and forest type, wildfire regime, hydroclimatic regime, and resulting hydrologic runoff response. Additionally, one high-elevation site with evidence of more recent wildfires in the last 400 years exhibits shorter residence times (<200 yrs).
These findings suggest that wildfire and projected increases in the the frequency and intensity of wildfires and extreme floods are likely to reduce sediment storage and residence times along mountain river corridors. Potential decrease in fine floodplain sediment retention along rivers is extremely important for carbon dynamics and ecosystems services, the stability of floodplains and risk to commonly associated societal infrastructure, and the fate and transport of contaminants including contaminated sediment from mines.
Difference between pre- and post-flood lidar complement 52 radiocarbon ages (used to estimate residence times) in identifying stream power, and valley confinement as significant predictors for floodplains disturbance in response to extreme floods. This means that while differences in vegetation, wildfire, and hydrology associated with elevation regulate the geomorphic response along river corridors of the study area, the shape of the valley and the landscape’s ability to dissipate energy during floods is also a determining factor as to where fine sediment will remain stable or be eroded.
This research was partially funded by my NSF Doctoral Dissertation Research Improvement Grant, two graduate student research grants from the Geological Society of America Quaternary Geology and Geomorphology Division, the Colorado Scientific Society, and scholarships from the Colorado State University Warner College of Natural Resources and Department of Geosciences.
Our research, led by Postdoctoral Fellow at Cornell University, Laurel Lynch, was just published in Nature Communications. This work expanded upon some of my PhD research and study sites in Rocky Mountain National Park and utilized Dr. Lynch’s expertise in biogeochemistry to examine the influence of hydrologic connectivity and channel complexity on aquatic carbon dynamics. Our findings show that river corridors with complex river channels in beaver meadows with beaver dams, canals, and multiple channels of flow across a single valley bottom create disparate zones with differences in organic carbon and metabolite composition. These spatial differences in organic carbon composition occur during low flow conditions in the late summer following peak flow.
During peak flow conditions in early June as a result of mountain snowmelt, organic carbon composition is similar across all channels. High flow causes water in numerous channels to become more connected and forces water from beneath the river channel and floodplain to the surface for mixing. These results are important for ecosystem productivity affected by land use management regarding the complexity of river channels, which society has a tendency to intentionally decrease. Changes in hydrologic flow regime associated with a shifting climate can also alter the functionality of these systems so that connectivity is decreased in complex channels, limiting temporal variation in connectivity in unaltered systems.
The first week of classes this semester at Case Western Reserve University, I took my Global Environmental Problems class to the Cleveland Museum of Contemporary Art (MOCA) to learn about environmental problems confronting water resources and freshwater ecosystems at Alexis Rockman’s exhibition, The Great Lakes Cycle.
Magnificent paintings provide a chronological representation of the environment beginning the last glacial maximum and progressing through the period of industrialization and resulting pollution and impact to water resources and various species. An amazing interactive learning tool, A Dive into The Great Lakes Cycle, created by scientist Jill Leonard and artist Taimur Cleary at University of Northern Michigan (UNM) was accessible at MOCA and can also be purchased for use outside of the museum.
Following our visit, I asked students to revisit the museum as groups assigned to each of the five primary paintings in the exhibit and to utilize the UNM website that dives deeper into the science behind the art, which involved 3 years of research by the artist and many references to scientific research.
Above is a photograph I took of Alexis Rockman’s painting titled “Watershed”, which address issues of urban industrial waste, freshwater contamination, genetically modified agriculture, food production and consumption, and environmental impacts that are often not seen on the surface, but underlay ongoing environmental issues.
As a follow up in class, students examined references including peer-reviewed scientific journals and government reports to interpret data and share with one another the themes they investigated more deeply in each painting. We used this exercise to discuss sources of data and information and the importance of investigating sources. In a follow-up class, the students from each painting group will present to the rest of the class their interpretations and the science behind the painting on which they focused.
Students in my hydrogeology course at Case Western Reserve University just turned in their write-ups from our field trip to the university’s Squire Valleevue and Valley Ridge Farm.
The university has a well field (shown below) that taps into an aquifer of Berea Sandstone (shown above in the outcrop of a nearby stream) confined above and below by Orangeville and Bedford Shale.
Using a generator and submersible pump, we conducted a pump test, during which the students measured draw down in the wells.
They installed a pressure transducer to record continuous data of depth to water.
We had some technical difficulties and mechanical challenges with pressure transducers and the sounding tape used to measure depth to water, but this provided a great opportunity for students to examine alternative methods and equations necessary to calculate aquifer properties with draw down data from only one well.
Students measured pumping rate to ensure a constant rate of pumping used in calculations of aquifer properties during the pump test.
Using the data they collected, students estimated aquifer properties including transmissivity, storativity, hydraulic conductivity, and discharge per unit width of aquifer.
They also conducted electromagnetic surveys using an EM31 to measure conductivity and relative changes in moisture in the shallow subsurface. Comparing depth to water values in the wells and differences in EM measurements from two weeks prior, students were able to infer relative changes in water table and aquifer levels.
The students set up differential GPS surveys to obtain the location and elevation of the wells and EM31 survey points.
Examination of topographic and geologic maps of the farm provided additional context to their surveys and examination of the GPS points in Google Earth.
Differential GPS surveys, examination of the well logs, and a hike along an incised stream to see exposures of the underlying stratigraphy allowed students to infer relative connectivity between the water table, nearby ponds, a stream, and the sandstone aquifer.
Examination of seepage faces at bedrock exposures and a closer look at the sandstone and shale provided insight into relative porosity and differences in hydraulic conductivity of the the different rock types. Visual examination of the rock types reinforce the understanding of differences between the sandstone aquifer and the shale aquitards.
The entire report aimed to provide hands-on experience with hydrogeological analysis, an understanding of water table and confined water connectivity, the role of underlying geology on the movement of groundwater, and a regional context for aquifer systems and local groundwater connectivity.
After developing and proposing to teach an experimental upper level undergraduate and graduate level course at Case Western Reserve University, I have received university approval to teach Spatial Analysis of Surficial Processes! I also recently received approval for my request to reserve an interactive learning room and computer lab in the Kelvin Smith Library. This will provide me with extra resources in teaching a course that integrates field observations with an introduction to geographic information systems (GIS), coding in R statistical software, applied multivariate and spatial statistics. The course will emphasize topographic analysis of digital elevation models and the presence and movement of water, soil, and sediment across the surface of the Earth. Because no GIS courses are currently taught on campus, I already have a variety of interest from graduate and undergraduate students in my home department (Earth, Environmental, and Planetary Sciences) as well as those in Civil Engineering and ecologists in the Biology Department!
My new position as a Visiting Assistant Professor in the Department of Earth, Environmental, and Planetary Sciences at Case Western Reserve University for the 2018 and 2019 academic year has just begun! This fall semester I am teaching an undergraduate and graduate Hydrogeology course while I work on getting out some more of my publications. In the spring, I will be teaching Global Environmental Problems and another course I am still designing. This new course will likely integrate aspects of geomorphology, hydrology, sustainability, and GIS. I am very excited about the opportunity to gain more teaching experience, this time at a private institution. These class sizes of 6 to 15 students are likely to be quite different than the course I taught in Vietnam, which had >90 students.