PAST RESEARCH & EXPERIENCE
LAKE MIXING DYNAMICS AND BIOGEOCHEMISTRY IN ARCTIC DELTAS
Lake mixing dynamics are well studied in many different biomes. However, lakes within the deltas of great Arctic rivers have been excluded from hydrodynamic studies, due to expense and fieldwork difficulties operating in the northern high latitudes. Biogeochemical studies based out of Arctic deltas have thus based their sampling regimes and extrapolating calculations on lake mixing dynamics studied elsewhere. However, a few studies have found discrepancies in greenhouse gas (GHG) accounting, particularly in regards to CH4 (methane). To address these uncertainties, I spent my PhD conducting hydrodynamic and biogeochemical research on lakes in the Mackenzie Delta.
By combining in situ thermistor arrays and climate stations with discrete CH4 sampling, both during open water and under ice, I discovered that these lakes do not behave like nearby tundra lakes. Instead, these shallow (<5 m deep) lakes develop strong chemical stratification over winter and are resistant to mixing at ice off, thereby delaying spring CH4 evasion to the atmosphere. I have subsequently developed theoretical models to cover a range of hydrologic, bathymetric, and biological lake conditions within the Delta.
MODELING STORMWATER FLOODING IN STEEP TROPICAL WATERSHEDS
Extreme weather events, like short-duration high-intensity rainfall that can cause major damage to infrastructure, are predicted to increase in the coming years with climate change. To prepare for such events and mitigate damages, I created a watershed-scale, hydrologic model of stormwater flow by replicating a major storm event in Waimanalo, Hawaii, that caused millions of dollars in damages in 2018. This simulation model let me pinpoint and assess potential flooding risks and develop best management practices (BMPs) based on FEMA recommendations.
By modeling extreme rainfall/storm events, we are able to generate information at numerous data-points that otherwise wouldn't be recordable. This allows planners and engineers to determine what type of stormwater controls are necessary throughout a municipality to best protect infrastructure and lives.
MODEL COMPARISON OF ROADWAY HARDENING IMPROVEMENTS AND THEIR WAVE ENERGY DISSIPATION EFFECTS
A project for the Hawaii DOT done in collaboration with colleagues at the Coastal Hydraulics Engineering Resilience (CHER) Lab at the University of Hawaii - Manoa. We designed and modeled five possible coastal roadway protections for the King Kamehameha Hwy near Hau'ula, Hawaii. Roadway hardening was necessary to improve shore structure to resist direct wave action run-up.
After designing revetments, we created models using Bouss-2D in SMS by Aquaveo. Results of modeling demonstrated which alternatives would best dissipate the wave energy specific to that area of coastline, and recommendations were made to the Hawaii DOT.
COMPARING HYDROLOGY ABOVE AND BELOW THE INTERMITTENT-PERSISTENT SNOW TRANSITION
"Mountain regions have steep climate gradients that substantially affect streamflow generation. To understand streamflow in mountainous catchments, both the seasonally and the intermittently snow‐covered areas within these catchments should be considered. By comparing water fluxes in seasonally and intermittently snow‐covered catchments and estimating their contributions to the regional watershed, we determined that discharge is low across the intermittent snow zone, but provides roughly one fourth of the regional flow. This highlights the importance of studying discharge generation across elevations," (Harrison et al., 2021).
Harrison, H. N., Hammond, J. C., Kampf, S., & Kiewiet, L. (2021). On the hydrological difference between catchments above and below the intermittent-persistent snow transition. Hydrological Processes.
ALLOCATION OF ALGAE IN NORTHERN LAKE MICHIGAN AFTER ZEBRA & QUAGGA MUSSEL INTRODUCTION
Following the introduction of the invasive zebra and quagga mussels to northern Lake Michigan, the ecology of this part of the lake has changed, moving from a mesotrophic to an oligotrophic regime. By studying phytoplankton distributions at nearshore and offshore locations around Beaver Island, we found that filtration of the water column by the mussel species has contributed to this regime change in a twofold way: first, by filtering pelagic algae out of the water column, and second by allowing benthic algal growth to increase due to deeper sunlight penetration following the filtration of pelagic algae.
This research was conducted as part of an REU with Central Michigan University's Biological Station and the Institute for Great Lakes Research. Photos courtesy of CMUBS.
