First Advisor

Jiunn-Der Duh

Date of Publication

Summer 8-30-2016

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Geography

Department

Geography

Language

English

Subjects

Soil moisture -- Remote sensing, Soil moisture -- Measurement, Landsat satellites, Wetland hydrology -- Oregon -- Tualatin River National Wildlife Refuge -- Case studies

DOI

10.15760/etd.3196

Physical Description

1 online resource (viii, 115 pages)

Abstract

This study compared two remote sensing water indices: the Normalized Difference Water Index (NDWI) and the Modified NDWI (MNDWI). Both indices were calculated using publically-available data from the Landsat 8 Operational Land Imager (OLI). The research goal was to determine whether the indices are effective in locating open water and measuring surface soil moisture. To demonstrate the application of water indices, analysis was conducted for freshwater wetlands in the Tualatin River Basin in northwestern Oregon to estimate hydrologic connectivity and hydrological permanence between these wetlands and nearby water bodies. Remote sensing techniques have been used to study wetlands in recent decades; however, scientific studies have rarely addressed hydrologic connectivity and hydrologic permanence, in spite of the documented importance of these properties. Research steps were designed to be straightforward for easy repeatability: 1) locate sample sites, 2) predict wetness with water indices, 3) estimate wetness with soil samples from the field, 4) validate the index predictions against the soil samples from the field, and 5) in the demonstration step, estimate hydrologic connectivity and hydrological permanence. Results indicate that both indices predicted the presence of large, open water features with clarity; that dry conditions were predicted by MNDWI with more subtle differentiation; and that NDWI results seem more sensitive to sites with vegetation. Use of this low-cost method to discover patterns of surface moisture in the landscape could directly improve the ability to manage wetland environments.

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Persistent Identifier

http://archives.pdx.edu/ds/psu/18488

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