Capstones 2026

Thursday, May 7th

All presentations will take place in the Rieke Science Center, room 113.

4:00-4:15pm, “360 Bike Park Erosion Susceptibility”
Garrett Armbruster
Erosion and destabilization of land surfaces and slopes is a common result of human activity liking building, development, and land management. Many studies have focused on how building roads, railways, and large housing developments impact local landslide and erosion hazards but less attention has been paid to the impact of recreational activities and areas. This study investigates how mountain biking impacts the erosion rates in small regions of Pierce County, WA. Using GIS analysis, I investigated how soil type and local slope correlate with the rates of trail erosion at Gig Harbor’s 360 Mountain bike park. My work found that most studied trails have similar amounts of erosion susceptibility. With minimal rates of erosion observed since the trails construction, likely due to lack of significant elevation change or slope across the park. These results show how we can track and manage erosion susceptibility within an area of concern. This may lead to better planning for future trails that are built within areas with major elevation change, and may prevent major disruption of trails.

4:15-4:30pm, “Assessing Urban Watershed Resilience: Pipers Creek as a Case Study”
Calvin Fisk
Urbanization has significantly altered the natural hydrologic cycle in many cities by increasing impervious surfaces such as roads and buildings. These surfaces prevent rainfall from soaking into the ground, causing more surface runoff to flow rapidly into nearby streams and increasing the risk of flooding. This research examines the Pipers Creek Basin in northwest Seattle as a case study to understand how urban stormwater management strategies can reduce runoff and improve watershed resilience in the Pacific Northwest. The study focuses on the effectiveness of green infrastructure projects implemented in the basin, particularly the Street Edge Alternatives (SEA) Street project and the Viewlands Cascade Drainage System. These projects were designed to mimic natural drainage by incorporating vegetation, soil infiltration areas, and modified street designs that slow and absorb stormwater. Previous research found that green infrastructure projects significantly reduced stormwater runoff and pollutant discharge into Pipers Creek. To evaluate the long-term effectiveness of these strategies, this project analyzes and integrates existing research literature, hydrologic monitoring data, and King County watershed reports, along with aerial imagery and field observations of the basin. By combining historical data with more recent observations, this research evaluates whether these systems remain effective and whether they could serve as a model for improving stormwater management in other urban watersheds.

4:30-4:45pm, “Influence of Sample Preparation on XRF Oxide Measurements”
Gairet Nason
X-ray fluorescence (XRF) is widely used in geology to rapidly measure the elemental composition of rocks in the field. These measurements commonly include major oxide values such as SiO₂, which are used to interpret igneous rock history and magma evolution. However, XRF measurements can be influenced by sample condition, including weathering, surface roughness, grain size, and preparation method. This study evaluates how sample preparation influences XRF oxide measurements by comparing raw/weathered surfaces, freshly cut surfaces, polished slabs, and powdered samples from a Manchester State Park rock sample and glass. Results show that raw surfaces were highly variable, cut and polished surfaces produced the most similar values, and powdered samples were reproducible but shifted away from cut/polished measurements. These findings show that XRF preparation method can shape geologic interpretation and should be reported alongside oxide data.

4:45-5:00pm, “AssessSing Future Landslide Susceptibility Under Increasing Rainfall Intensity in Tacoma, Washington”
Sabrina Humphrey
This capstone project investigates how projected increases in precipitation intensity may influence landslide occurrence in Tacoma, Washington. Tacoma has steep coastal bluffs and river valleys made of loose glacial sediments that easily absorb water, making them prone to landslides during heavy rain. Although total yearly rainfall in western Washington may not change much, climate projections from the University of Washington Climate Impacts Group show that extreme rain events are expected to become more intense by the mid-21st century. This study combines several data sources in GIS, including a lidar-based landslide inventory from the Washington Geological Survey, historical rainfall data from NOAA and PRISM, downscaled climate projections, and detailed elevation data. It also uses a completed ArcGIS landslide susceptibility map that shows slope steepness, past landslides, and average rainfall. By layering projected increases in rainfall intensity over areas that are already unstable or highly susceptible, this project evaluates where landslides may become more likely in the future. The goal is to identify potential hazard “hot spots” and support better hazard planning and risk awareness for Tacoma communities.