Date of Award

Fall 2020

Document Type

Geospatial Analysis Masters Capstone

Degree Name

Master of Science

Department

Geography

Department Chair or Program Director

Gallagher, Jackie

First Advisor

Millones Mayer, Marco

Second Advisor

Gallagher, Jackie

Third Advisor

Parmentier, Benoit

Major or Concentration

Geospatial Analysis

Abstract

Landslides occur when a slope is unstable and collapses with different contributing and mediating factors to slope instability, including human activity. This study evaluates the association between the occurrence of landslides and irrigation in Franklin County, Washington. The study sought to evaluate whether irrigation can be linked to an increase in the occurrence of landslide events within Franklin County. The study area was divided into a ‘treatment site’ and several ‘control sites.’ The treatment site is located in Franklin County where irrigation has occurred near the cliff, while the control sites are sloped and non-irrigated areas outside of Franklin County. Control and treatment areas share the same characteristics in terms of underlying geology and slope. Therefore, the likelihood for landslide events is comparable for both types of areas, except for the presence or absence of irrigation. The study spans 20 years; from 2000 to 2019. For each year, landslide events were extracted using the Digital Elevation Model (DEM) differencing method and verified with visual analysis of false color composites. Results show that eight landslides were identified in irrigated areas while two landslides were detected in non-irrigated areas, for a total of 729 pixels. I used a Generalized Linear Model (GLM), specifically the Binomial specification/Logistic Regression to determine the importance of irrigation on the occurrence of landslides identified. Pixels located within irrigated areas were found to be 32.5 to 36.3 times more likely to have landslides occur than if no irrigation occurred. Several different versions of the GLM were explored, and the rate at which irrigation effects landslides changes depending on which variables were included. The results of this study can be used to advocate for more environmental regulations where irrigation occurs on slopes. Limitations of this research include data restraints and study area restrictions. Future work can further investigate the study area or develop additional methods.

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